Dissertations / Theses on the topic 'Agroforestery Systems'

Le changement climatique et la variabilité ont des répercussions graves dans le secteur agricole des régions tropicales. Le secteur du café est sensible au changement climatique car il nécessite une température relativement froide et une plus grande durée des pluies. L'adaptation au changement climatique dans l'agroforesterie du café est donc importante pour traiter les impacts, mais il existe des obstacles et des limites. Le but de cette thèse était d'analyser les stratégies d'adaptation au changement climatique au centre du Kenya. Nous avons étudié différentes étapes de l'adaptation qui incluent (1) les connaissances sur le changement climatique et l'adaptation, la motivation à l'adaptation, (2) le choix actuel des stratégies d'adaptation et leurs déterminants, (3) les rôles du système d'innovation et du contexte institutionnel. Cette étude repose sur quatre sources d'information: - (1) groupes de discussion sur des questionnaires pré-définis, (2) enquêtes auprès des ménages, (3) entrevues auprès des intervenants et (4) données climatiques historiques sur le contexte de quatre types de systèmes de productions dans l’agriculture : les cultures vivrières, le café spécialisé, les systèmes diversifiés café-laiterie et les systèmes laitiers spécialisés, dans les zones caféières et vivrières. L'analyse des tendances de Mann-Kendal et l'estimateur de la pente de Sen ont été utilisées pour comparer les connaissances des agriculteurs sur les changements climatiques et l’historique des données climatiques, tandis que le modèle de Heckman a été utilisé pour analyser les stratégies d'adaptation et leurs déterminants. Les résultats soulignent des cohérences entre les connaissances des agriculteurs et l'analyse historique des données pour la température mais des incohérences avec le changement des précipitations. L'analyse de la perception par les agriculteurs révèle que les précipitations diminuent radicalement au fil du temps, alors qu'aucun élément de preuve concernant les précipitations ne permet d'appuyer la perception des agriculteurs. L'incohérence est donc corroborée par l'analyse des modèles. Les agriculteurs du secteur du café et des cultures vivrières se sont adaptés différemment aux changements climatiques. Les agriculteurs qui sont conscients des changements sont plus disposés à explorer les stratégies d'adaptation. Une partie des agriculteurs qui ne perçoivent pas le changement climatique adoptent des stratégies d’adaptation à des facteurs autres. L'adaptation au changement climatique est également déterminée par la performance institutionnelle et les différences de systèmes sectoriels d'innovation. La comparaison entre les secteurs du café et des produits laitiers révèle ainsi que les stratégies des acteurs du café sont limitées. En ce qui concerne l’élaboration des politiques, cette thèse contribue aux politiques d’accompagnement de l’adaptation au niveau des ménages, aux politiques de recherche agronomique et de négociation des accords internationaux. Les recommandations politiques au niveau des ménages se différentient selon trois scénarios. En premier lieu de l’intensification dans le café par l’innovation technologique. Les deux autres options politiques sont dans la diversification sectorielle dans la production laitière qui dépend de leur niveau de rentabilité. Les résultats de cette étude sont issus d’enquêtes sur l’analyse des systèmes d’innovation. D’autres options politiques sont proposées dans le développement de nouvelles infrastructures, des subventions pour accroitre les potentiels d’adaptation. Nous recommandons enfin de nouveaux sujets de recherche pour le futur
Climate change and variability is the most widespread anthropogenic challenge affecting agricultural production and productivity particularly in the tropics. Coffee sector is sensitive to climate change as it requires relatively cold temperature and higher rainfall duration. Adaptation to climate change in the coffee agroforestry is, therefore, important to address the impacts, but there are barriers, and limits. The aim of this Thesis was to analyze the adaptation strategies to climate change in Central Kenya. We studied the steps in adaptation, which includes (1) the knowledge on climate change and adaptation, the motivation towards adaptation, (2) current choices of households’ adaptation strategies, and their determinants, (3) the roles of innovation system and institutional context to support adaptation. This study was based on four sources of information: - (1) Focus Group Discussions to predefine the questionnaires, (2) household surveys, (3) stakeholders interview, and, (4) historical climate data. The data collection considered four farming typologies; - food crops, specialized coffee, diversified coffee-dairy and specialized dairy farming systems in the coffee and food crops zones. Mann-Kendal trend analysis and Sen’s slope estimator were used to compare the farmers’ knowledge of climate change with the historical climate data, while Heckman model was used to analyze adaptation strategies and their determinants. The findings explore consistent results between farmers’ knowledge and historical data analysis for temperature, while inconsistency is observed in rainfall change. Analysis of farmers’ perception revealed rainfall is radically declining over time, while no evidence in rainfall record is found to support the farmers’ perception. The inconsistency is therefore, substantiated with analysis of patterns. Coffee and food crop farmers are found to adapt to climate change differently. Farmers who are aware of the changes are found more willing to explore adaptation strategies although some of the farmers who do not perceive the climate is changing are also adopting strategies for factors other than perception. The comparison between coffee and dairy sectors found that actors in the coffee are limited, the system is highly centralized with limited options for farmers to process and market their products, while the dairy sector is informally controlled by demand based business and comparatively, numerous actors. We conclude in this study that the patterns in rainfall affects the farming activities of the study area higher than the annual changes. Consequently, farmers adopt a series of adaptation strategies in response to their perception of changes in climate and economic pressure in the farm. This adaptation to climate change also depends on the nature of actors’ interaction and institutional context. In relation to policy development, this Thesis contributes to household level adaptation policies, research policies and international agreements and negotiations. The household level policy recommendations consists of three scenarios. Farmers’ intensification in coffee applying the right technological innovations. The second and third policy options are the diversification to dairy and complete sectoral transformation to dairy depending on the profitability and adaptation level of the sectors. The results in this study are derived from surveys and analysis of innovation systems. Other strategies such as new infrastructural development and institutional subsidies could be potential for adaptation. We therefore, recommend, these could be potential future research topics

The potential of agroforestry in the British uplands depends largely on the ability of system components to efficiently use resources for which they compete. A typical system would comprise conifers planted at wide spacing, with sheep grazing pasture beneath. Computer models were developed to investigate the growth of trees and pasture in a British upland agroforest system, assuming that growth is primarily a function of light intercepted. Some of the implications of growing trees at wide spacing compared to conventional spacings, and the impact of trees on the spatial and annual production of pasture, were examined. Competition for environmental resources between trees and pasture was assumed to be exclusively for light: below-ground interactions were ignored. Empirical methods were used to try and predict timber production in agroforest stands based on data for conventional forest stands, and data for widely-spaced radiata pine grown in South Africa. These methods attempted to relate stem volume increment to stand density, age, and derived competition measures. Inadequacy of the data base prevented successful extrapolation of growth trends of British stands, although direct extrapolation of the South African data did permit predictions to be made. A mechanistic individual-tree growth model was developed, both to investigate the mechanisms of tree growth at wide spacings, and to provide an interface for a pasture model to examine pasture growth under the shading conditions imposed by a tree canopy. The process of light interception as influenced by radiation geometry and stand architecture was treated in detail. Other features given detailed consideration include carbon partitioning, respiration, the dynamics of foliage and crown dimensions, and wood density within tree stems. The predictive ability of the model was considered poor, resulting from inadequate knowledge and data on various aspects of tree growth. The model highlighted the need for further research into the dynamics of crown dimensions, foliage dynamics, carbon partitioning patterns and wood density within stems, and how these are affected by wide spacing. A pasture model was developed to investigate growth beneath the heterogeneous light environment created by an agroforest tree canopy. Pasture growth was closely related to light impinging on the crop, with temperature having only a minor effect. The model highlighted the fact that significant physiological adaptation (increased specific leaf area, decreased carbon partitioned below-ground and changes in the nitrogen cycle) is likely to occur in pasture shaded by a tree canopy.

While the light regimes of closed forest strands and open pasture have been quantitatively described and modelled, agroforestry involves greater complexity and spatial variability. This research involved intensive measurement of quantum flux density (QFD) above and below re-spaced tree strands of Sitka spruce (Picea sitchensis [Bong.] Carr.) and hybrid larch (Larix x eurolepis Henry) in conjunction with measurement of tree growth. QFD was also measured above and below pasture growing in boxes in imported soil sunk to ground level beneath the trees. The Monteith hypothesis that crop growth in unstressed conditions is linearly related to the amount of QFD intercepted by its canopy was found to hold for above ground growth of trees at agroforestry spacings. The overall dry matter: QFD quotient (e) for Picea sitchensis across the range of tree frequencies was 0.32 g mol^-1 which is lower than typical values reported for agricultural crops, young container grown trees of Salix viminalis and Populus trichocarpa and closed-canopy Picea sitchensis, but comparable with previous estimates for a range of mature tree stands. e was unaffected by tree spacing, but was significantly higher for the tall tree stand which had been pruned. The mean annual QFD transmitted to the understorey varied from 39% to 96% of that in the open across the agroforestry treatments. The mean transmittance was similar but spatial variability of QFD was significantly higher in tree stands with crown to ground level when compared with stands having similar crown dimensions but which had been pruned to approximately 1.3 m height. More than 90% of seasonal pasture growth could be explained by a regression of growth on incident QFD.

Air pollution can lead to environmental impacts. Over the past decades there have been some success stories reducing pollutant emission, namely sulphur dioxide (SO2). However, impacts on ecosystems from atmospheric nitrogen (N) pollution are still seen as a major threat for European biodiversity. Across Europe over 70% of Natura 2000 sites are at risk for eutrophication with over 70% of the Natura 2000 area in Europe (EU28( exceeding critical loads for nutrient nitrogen deposition. Agricultural ammonia is a key contributor to the threat to these sites due to the close proximity of agricultural activities and protected sites. Source attribution modelling using an atmospheric transport model showed that agricultural livestock production in the UK is the dominant nitrogen source for N disposition across the UK Natura 2000 network. Nearly 90% of all sites had livestock as their dominant source, contributing 32% of the total nitrogen deposition across the whole network. 76% of all Special Areas of Conservation (SAC) sites exceeded their critical load for nutrient nitrogen, representing 74% of the entire SAC area. The extent of exceedance is also notable with many sites experiencing depositions of >50 kg N/ha/yr over the critical load. the situation for acidity critical load exceedance is less sever, by 51% of sites are still exeeded. Legislation to regulate pollutant emissions to air and protect biodiversity are often not integrated, and there has been no common European approach for determining the impacts of nitrogen deposition on individual Natura sites, or on conservation status. Off-site sources of air pollution present difficulties in assessing and attributing impacts, because deposition can result from local sources (1-2 km), or very far away sources (>1000 kms). Managing nitrogen losses on the farm and improving the efficient use of nitrogen are key components for overall reduction in NH3 emissions. Many nitrogen management options are available to abate ammonia from agricultural activities. On the one hand, technical and management measures include controlling emissions from manure storage and spreading, livestock feeding strategies, and improving housing systems. Trees, on the other hand, are effective scavengers of both gaseous and particulate pollutants from the atmosphere, making tree belts potentially effective landscape features to support ammonia abatement strategies. Using a coupled deposition and turbulence model the recapture efficiency of tree planting around ammonia sources was estimated. Using different canopy structure scenarios, tree depths and differing leaf area density (LAD) and leaf are index (LAI) were adjusted for a main canopy and a backstop canopy. Recapture efficiency for ammonia ranged from 27% (trees planted around housing systems), up to 60% (under-story livestock silvopastoral systems). Practical recapture potential was set at 20% and 40% for housing and silvopastoral systems respectively. Model results from scaling up to national level suggest that tree planting in hot spot areas of ammonia emissions would lead to reduced N deposition on nearby sensitive habitats. Scenarios for on-farm emission control through tree planting showed national reductions in nitrogen deposition to semi-natural areas of 0.14% (0.2 kt N-NHx) to 2.2% (3.15 kt N-NHx). Scenarios mitigating emissions from cattle and pig housing yielded the highest reductions. The afforestation strategy showed national-scale emission reductions of 6% (8.4 kt N-NHx) to 11% (15.7 kt N-NHx) for 25% and 50% afforestation scenarios respectively. Increased capture by the planted trees also generated an added benefit of reducing long-range transport effects, including a decrease in wet deposition of up to 3.7 kt N-NHx (4.6%) and a decrease in export from the UK of up to 8.3 kt N-NHx (6.8%). Agroforestry measures for ammonia abatement were shown to be cost-effective for both planting downwind of housing and in silvopastoral systems, when costs to society were taken into account. Planting trees was also cost-effective from a climate change perspective. Comparing the cost per kg of NH3 abated showed that planting trees is a method of ammonia emission mitigation comparable with other (technical) measures. The costs for planting trees downwind of housing were calculated at €2.6-7.3/kg NH3. Agroforestry for ammonia abatement offers multiple benefits for the farmer and synergistic effects for society as a whole including i) carbon sequestration. ii) visibility screening around housing units, iii) imporved animal welfare for silvopastoral systems, iv) reducing critical load exceedance on protected sites, v) price advantage of 'woodland chick' productions, vi) supporting the Industrial Emission Directive (IED) requirements for emission reduction, vii) supporting national afforestation policies. The results of this work support the notion that in the emerging discussion about the values of ecosystem services and the role of nature-based solution to tackle persistent environmental challenges, tree planting has a large potential in rural and urban environments.

L’ajout de diversité végétale est présenté comme un moyen d’améliorer la durabilité des agrosystèmes. Cependant, il y a encore des manques importants de connaissances sur l’effet de la diversité végétale sur les processus à la base de l’élaboration des rendements. Les systèmes agroforestiers tropicaux couvrent une large gamme de diversité végétale ; ce sont donc de bons modèles pour étudier la relation entre diversité et productivité. Les systèmes agroforestiers de la région de Talamanca au Costa Rica sont particulièrement intéressants car au sein de communautés végétales complexes, ils comprennent des bananiers et des cacaoyers qui sont des cultures de rente importantes et dont la production peut facilement être quantifiée et analysée. Une autre spécificité de ces systèmes est qu’ils présentent des organisations spatiales particulièrement diverses. Analyser comment la diversité des plantes et son organisation influe sur les performances de ces systèmes est particulièrement complexe et nécessite le développement de nouvelles approches. Les objectifs de cette thèse étaient d’étudier : i) quels facteurs affectent la relation entre diversité végétale et productivité ? ii) Comment la diversité végétale influence la productivité globale des systèmes agroforestiers ? et iii) Comment la structure spatiales des communautés de plantes cultivées influence leurs rendements ?Tout d’abord, une méta-analyse a été menée afin d’étudier la relation entre diversité végétale et production dans une très large gamme de systèmes naturels et cultivés. Cette analyse a notamment traité du rôle de la latitude, du climat et de la structure de la canopée sur cette relation. Elle a montré que le gain lié à la diversité végétal tend à diminuer avec la magnitude de cette diversité. Nos résultats montrent également que la réponse de la productivité à la richesse spécifique en plantes dépend énormément du type de communauté considéré, notamment si la communauté comprend des arbres.Ensuite, un réseau de 180 placettes situées dans 20 parcelles d’agriculteurs a été étudié dans la région de Talamanca. Pendant un an, la production de chaque plante a été évaluée. Cette production a ensuite été convertie en revenus en accord avec les prix du marché local. Alors qu’un effet positif de la diversité végétale cultivée a été observé sur le revenu globale (de chaque placette), cet effet était très contrasté si on le considérait séparément pour les différents groupes fonctionnels. Cet effet était positif pour les plantes des groupes appartenant aux strates hautes et négatif pour les plantes des groupes appartenant aux strates basses. Ces résultats suggèrent que la complémentarité entre plantes était plus forte pour les plantes des strates hautes et qu’inversement la compétition était plus forte dans les strates plus basses.La seconde phase de l’analyse des données de ce réseau de parcelles a visé à étudier l’effet du voisinage de chaque bananier ou cacaoyer sur leur production. Une approche d’analyse individu-centrée a été développée afin de déterminer si le nombre de voisins d’un groupe donné dans un rayon donné était un bon prédicteur de la croissance ou du rendement de chaque bananier ou cacaoyer. Les résultats montrent que la distance à laquelle la production d’un bananier ou d’un cacaoyer est affectée par ses voisins dépend de la taille de ces. De manière surprenante, les grands arbres ont eu un effet plus faible que les arbres plus petits. Cela suggère que des densités modérées de grands arbres pourraient être compatibles avec une production de bananiers et de cacaoyer avec un haut niveau de rendement. Ces résultats ont été discutés en termes de complémentarité et compétition pour la lumière. Des pistes d’organisation sont proposées et discutées au regard de la maximisation des rendements des cultures de rente et des autres cultures mais aussi dans la provision de services écosystémiques au sens large
Adding plant diversity is increasingly presented as a mean to improve the sustainability of agrosystems. However, there is still a lack of knowledge on how plant functional diversity alters processes that support production. Because they cover a broad range of plant diversity, agroforestry systems in the tropics are a good case study to better understand the diversity-production relation. Agroforestry systems in the Talamanca region in Costa Rica are particularly interesting because among the cultivated plants they encompass, banana and cacao are two cash crops of major importance and for which production can easily be quantified and analyzed. Another specificity of these systems is that their vertical and horizontal organization is particularly diverse. Understanding how plant diversity and its organization alter the performances of these complex systems is particularly challenging and requires developing new approaches. The objectives of this thesis were to address the following questions: i) Which factors affect the relationship between plant diversity and productivity? ii) How plant diversity influences the global productivity of agroforestry systems? and iii) How the spatial structure of the plant community affects yields?First, a meta-analysis was carried out to address the diversity-production issue among a very broad range of systems world-wide. This analysis focused on how latitude, climate, and canopy structure modify the effect of plant richness on productivity of agricultural and natural ecosystems. It showed that the gain per unit of diversity added decreased as plant richness increased. Our findings also showed that the response of productivity to plant richness largely depends on the type of plants in the community, especially if the community includes trees.Then, we extensively studied the diversity and the productivity of 180 plots located within 20 fields in the Talamanca region. A global evaluation of the productivity of these systems was possible with the estimation of the production of each plant during 1 year. This production was converted into income according to local market prices. While we observed a global positive effect of plant diversity on global income, this effect was contrasted according to the functional group considered (banana, cacao, other fruits, timber, firewood. When considering the functional group separately, there was a positive effect of plant diversity for higher strata groups and a negative effect for lower strata groups. This suggested that complementarity between plants was stronger than competition for those plants occupying the higher strata of the canopy but that competition was stronger than complementarity for plants occupying the lower strata of the canopy.The second part of the analysis of the Talamanca fields dataset focused on the effect of neighbouring plants on the production of banana and cacao plants. An individual-based analysis was developed to determine whether the number of neighbouring plants of a given functional groups explained the potential yield of each banana or cacao plant. We found that the distance at which other plants alters the yield of banana or cacao plants was greater for larger functional groups (fruit or wood trees) than for smaller ones (cacao trees or banana plants). Interestingly, higher strata trees had a smaller effect than lower strata trees, suggesting that moderate densities of tall trees could be compatible with high banana and cacao production. These findings were discussed in terms of complementary and competition with respect to the availability of light at higher and lower strata of the canopy. On an applied perspective, our results suggest that productivity could be maximized by a reasonably number of plant species, and then we proposed new direction to organize fields in order to maximize the production of cash crops while providing supplementary income for farmers and ecosystem services

Le débat sur d’autres façons de faire de l’agriculture est nécessaire et urgent. Les crisesqui ravagent la société mettent de plus en plus en évidence l’importance d’adapter lespratiques, les techniques et les outils pour produire dans les territoires rurauxd’Amazonie. L'agriculture familiale, y a pendant des siècles été fondée sur une pratiqueconsistant à couper et brûler la forêt, liée à l'agriculture itinérante. Des facteurs récentstels que la croissance démographique et la demande alimentaire ont intensifié les zonesde production pour répondre à la demande du marché. Cela met en danger desressources naturelles telles que l’eau, le sol et l’air. Repenser les modes de production etles systèmes de production est un point clé pour parvenir à une agriculture familialecapable de répondre aux aspects fondamentaux de la durabilité. En ce sens, les systèmesagroforestiers (SAF) sont une alternative adoptée par des agriculteurs familiauxd'Amazonie, car ils sont bien adaptés aux diverses réalités de la région, mais cessystèmes se répandent lentement. Ainsi, la présente recherche vise à identifier lesaspects liés aux barrières qui empêchent l'adoption et/ou la diffusion des SAF enagriculture familiale et les stratégies possibles à adopter qui peuvent contribuer à lessurmonter dans les territoires ruraux de l'Amazonie. La recherche a été menée dans leszones de plaine inondable d'Igarapé-Miri et sur les terres fermes de Tomé-Açu, dansl'est de l'Amazonie, en adoptant une approche de recherche qualitative-quantitative, àdes fins exploratoires et descriptives. À la fin de la recherche, comme principauxrésultats, nous avons identifié que la recherche sur les SAF s'est concentrée sur un débatplus socio-environnemental, tandis que les principales barrières identifiées tant auniveau de la propriété qu'aux multiniveaux spatiaux Local/Territorial etRégional/Fédéral, les facteurs limitant l’adoption des SAF sont liés à des facteurs socioéconomiques.Un autre résultat est de considérer à la fois les spécificités del'environnement biophysique pour structurer ces systèmes et les techniques à utiliserpour les mettre en oeuvre, en considérant divers aspects des exploitations tels que ladisponibilité de la main d'oeuvre, les ressources financières, le temps, le matériel, lesintrants, entre autres. Enfin, un autre résultat extrêmement important que nous avonsidentifié est lié aux relations de coopération et à la création de réseaux sur le territoire:ils s'avérent être des éléments stratégiques et fondamentaux pour surmonter les barrièresrencontrées et ainsi accompagner les agriculteurs familiaux dans la transitionagroécologique
The debate on other ways of farming is necessary and urgent. The crises that areravaging society increasingly highlight the importance of adapting practices, techniquesand tools to produce in rural areas of the Amazon. For centuries, family farming hasbeen based on a practice that consists of cutting and burning the forest, linked toitinerant agriculture. Recent factors, such as population growth and the demand forfood, have increased the production areas to meet market demand. This endangersnatural resources such as water, soil and air. Rethinking production methods andsystems is a key point to achieve family farming capable of meeting the fundamentalaspects of sustainability. In this sense, agroforestry systems (AFS) are an alternativeadopted by family farmers in the Amazon, as they are well adapted to the diverserealities of the region, but these systems are spreading slowly. Thus, the presentresearch aims to identify the aspects related to the barriers that prevent the adoptionand/or diffusion of AFS in family farming and the possible adoption strategies that cancontribute to overcoming them in rural areas of the Amazon. The research wasconducted in the floodplain areas of Igarapé-Miri and on the mainland of Tomé-Açu,Eastern Amazon, adopting a qualitative-quantitative research approach, withexploratory and descriptive purposes. At the end of the research, as main results, weidentified that research on SAF has focused on a more socio-environmental debate,while the main barriers identified both at the property level and at the multi-level spatiallevels Local/Territorial and Regional/Federal, the factors that limit the adoption of SAFare linked to socioeconomic factors. Another result is to consider both the specificitiesof the biophysical environment to structure these systems and the techniques used toimplement them, considering various aspects of the farms such as availability of labor,financial resources, time, materials, inputs, among others. Finally, another extremelyimportant result that we identified is linked to cooperation relationships and the creationof networks in the territory: they reveal strategic and fundamental elements to overcomethe barriers encountered and thus support family farmers in the agroecologicaltransition
O debate sobre outras formas de fazer agricultura é necessário e urgente. As crises queassolam a sociedade destacam cada vez mais a importância da adaptação de práticas,técnicas e ferramentas para produzir nos territórios rurais da Amazônia. A agriculturafamiliar baseou-se durante séculos numa prática que consiste no corte e queima dafloresta, ligada à agricultura itinerante. Fatores recentes, como o crescimentopopulacional e a procura de alimentos, intensificaram as áreas de produção parasatisfazer a procura do mercado. Isto põe em perigo recursos naturais como a água, osolo e o ar. Repensar os métodos e sistemas de produção é um ponto chave paraalcançar uma agricultura familiar capaz de atender aos aspectos fundamentais dasustentabilidade. Nesse sentido, os sistemas agroflorestais (SAFs) são uma alternativaadotada pelos agricultores familiares na Amazônia, pois estão bem adaptados àsdiversas realidades da região, mas esses sistemas estão se espalhando lentamente.Assim, a presente pesquisa tem como objetivo identificar os aspectos relacionados àsbarreiras que impedem a adoção e/ou difusão do SAF na agricultura familiar e aspossíveis estratégias de adoção que possam contribuir para superá-las nos territóriosrurais da Amazônia. A pesquisa foi realizada nas áreas de várzea do Igarapé-Miri e nocontinente de Tomé-Açu, Amazônia Oriental, adotando uma abordagem de pesquisaquali-quantitativa, com fins exploratórios e descritivos. Ao final da pesquisa, comoprincipais resultados, identificamos que a pesquisa sobre SAF tem se concentrado emum debate mais socioambiental, enquanto as principais barreiras identificadas tanto nonível da propriedade quanto nos multiníveis espaciais Local/Territorial eRegional/Federal, o os factores que limitam a adopção do SAF estão ligados a factoressocioeconómicos. Outro resultado é considerar tanto as especificidades do ambientebiofísico para estruturar esses sistemas quanto as técnicas utilizadas para implementálos,considerando diversos aspectos das fazendas como disponibilidade de mão de obra,recursos financeiros, tempo, materiais, insumos, entre outros. Por fim, outro resultadoextremamente importante que identificamos está ligado às relações de cooperação e àcriação de redes no território: revelam-se elementos estratégicos e fundamentais parasuperar as barreiras encontradas e assim apoiar os agricultores familiares na transiçãoagroecológica

Face aux besoins croissants pour une production agricole durable, les systems de culture évoluent vers des systèmes qui accomplissent des objectifs environnementaux et agricoles multiples. La recherche en conception de systèmes de cultures (CSC) s'intéresse à l'effet des pratiques et de l'environnement sur les systèmes de culture et leur performance. L'interaction entre production et services ecosystémiques, et la quantification de ces relations, sont un aspect clé de ce domaine de recherche. Une variété d'approches ont été théorisées, tels que l'utilisation de modèles et la mobilisation de connaissances expertes. Les modèles permettent de tester rapidement et à faible coût l'effet de pratiques agricoles dans une variété de conditions, mais l'application de conclusions théoriques à la parcelle peut être limitée par des contraintes locales ainsi que des obstacles à la communication chercheur-agriculteur. Mobiliser les agriculteurs et autres acteurs pertinents pour la CSC peut aider à surmonter ces obstacles ; cependant, cela limite l'innovation au cadre des connaissances expertes.L'objectif de cette thèse est de combiner la modélisation et des méthodes participatives pour une méthode de CSC qui exploite le potentiel de la modélisation numérique tout en s'assurant que les solutions proposées prennent en compte les contraintes environnementales et socioéconomiques. Après avoir revu l'état d'avancement de la recherche en prototypage et en CSC, nous proposons un cadre méthodologique divisé en quatre parties ; a) combiner une typologie des pratiques et un modèle conceptuel pour évaluer la diversité des pratiques, contraintes et trade-offs dans une zone de production ; b) acquérir des données de terrain pour quantifier les trade-offs pertinents entre production et services écosystémiques ; c) sélectionner et préparer un modèle numérique approprié pour simuler les effets des pratiques sur la production et l'apport de services ; et d) évaluer si l'interaction d'agriculteurs avec le modèle numérique peut générer des systèmes de culture potentiels qui répondraient aux objectifs agro-environnementaux posées (apport d'un service écosystémique) ainsi qu'être acceptables pour les agriculteurs qui les adapteraient à l'expérimentation dans leurs parcelles.The systèmes agroforestiers à base de café (cafés/arbres d'ombrage) du Costa Rica central ont étés le système de culture choisi pour répondre à ces questions. Les systèmes agroforestiers offrent de nombreuses occasions d'étudier et évaluer les services écosystémiques apportés, en plus de la production principale. L'association de deux cultures pérennes place l'évaluation de la performance à long terme et de la durabilité des systèmes au centre de la question. La culture du café au Costa Rica fait vivre une part importante de la population, et est aussi basée sur la gestion intensive d'une culture à haute valeur d'exportation, vulnérable aux fluctuations des prix sur le marché mondial ainsi qu'au changements climatiques. Des pentes raides et une saison des pluies importante créent des problèmes d'érosion significatifs ; cependant, certaines pratiques de contrôle de l'érosion (utilisation d'arbres d'ombrage et d'adventices) impactent la production de café. La réconciliation de ces deux aspects nous offrent l'occasion de tester notre cadre méthodologique dans une situation où une solide argumentation technique serait nécessaire pour encourager les expérimentations dans les parcelles. Enfin, le dernier chapitre porte une réflexion d'ensemble sur l'importance de choisir et préparer correctement un modèle agronomomique adéquat, les application potentielles de cette méthodologie, ainsi que les recommandations que nous avons pu effectuer en termes de pratiques de contrôle de l'érosion dans la zone d'étude
In the face of increasing concerns about sustainability of agricultural production, cropping systemsare evolving towards systems that fulfill multiple agronomic and environmental objectives. Researchin cropping systems design (CSD) is concerned with studying the effect of farming practices oncropping systems and their performance. The interaction between production and ecosystemservices, and quantification of trade-offs between the two, is a key aspect of this research. A varietyof approaches have been theorized, such as use of models and mobilization of expert knowledge.Models allows fast and low-cost testing of the effect of farming practices under a variety ofconditions, but the application of theoretical outcomes to on-farm changes can be limited by localconstraints and researcher-farmer communication. Mobilizing farmers and other relevantstakeholders for CSD can help overcome these obstacles; however this limits innovation to the scopeof expert knowledge.The objective of this thesis is to combine modeling and participatory methods for a CSD frameworkthat harnesses the potential of numerical modeling while ensuring the proposed solutions take intoaccount socioeconomic and environmental constraints. After an overview of current advances inprototyping and CSD, we propose an methodological framework divided into four parts; a) combininga typology of farming practices and a conceptual model to appraise the diversity of farming practices,constraints and trade-offs at the plot scale in a defined production area; b) collection of field data forquantifying relevant trade-offs between production and ecosystem services; c) selecting andpreparing an appropriate numerical model for simulating the effects of farming practices onproduction and provision of ecosystem services; and d) evaluating whether the interaction of farmerswith a numerical model can generate candidate cropping systems that fulfill our agro-environmentalobjectives (provision of ecosystem service) as well as being suitable for the farmers who will adaptthem for on-farm experimentation.The coffee-based agroforestry systems (coffee/shade trees) of central Costa Rica were the chosenproduction system for answering these questions. Agroforestry systems offer plentiful opportunitiesfor valuing ecosystem services in addition to crop production; the combination of two perennialcrops brings long-term performance assessment and sustainability of the system to the heart of thequestion. Coffee cultivation in central Costa Rica concerns a large amount of livelihoods, but is alsobased on intensive management of a highly valued cash crop vulnerable to price fluctuations on theglobal market as well as climate change. Steep slopes and heavy rainfall also cause high levels of soilerosion; yet certain indirect erosion control practices (such as the use of shade trees of weeds) alsohave an impact on coffee production. The reconciliation of these two aspects offers the opportunityto test our methodological framework in situations where precise discussions onproduction/environment trade-offs are needed.Finally, in the last chapter we reflect on the importance of correctly choosing and preparing the rightmodel for the job, potential application of this methodology, as well as the recommendations wereable to make in terms of erosion control practices in the study area

A prototype agroforestry system, which combined the low-input features and environmental benefits of the traditional Indonesian multi-species 'jungle rubber' system with high yielding rubber clones developed in monoculture plantations, was tested under on-farm conditions. Secondary forest was allowed to regenerate between weeded rows of clonal rubber. Clonal rubber establishment was studied, and the interactions between it, secondary forest species and farmer management were investigated using a combination of researcher- and farmermanaged weeding trials. In one trial, alteration of below-ground resources (using root barriers and trenches to create three soil volumes) did not affect above or below-ground growth of clonal rubber, although weeding significantly increased stem diameter and volume. It was concluded that secondary forest regrowth interfered with resource capture at the level of individual roots; interference was not due to depletion of total available resources. Shoot:root ratios and ratios of horizontally- to vertically-oriented proximal roots were not affected by weeding. Growth of clonal rubber in N-fertilised plots, in the presence of weeds, was significantly greater than in corresponding unfertilised plots, indicating that N-addition may overcome some negative effects of competition in the system. However, a bioassay of nutrient limitation showed no significant differences in root biomass or root-length density, for either rubber or weed rootingrowth into soil cores enriched with various nutrients. The second researcher-managed trial, on steep slopes, showed that the survival rate of clonal rubber was 33% higher than that of the 'seedling' rubber variety traditionally used, and that mean stem height and diameter of clonal rubber trees were significantly greater than those of seedling rubber, 21 months after planting. Damage to trees by banded leaf monkeys (Presbytis melalophos nobilis) and feral pigs (Sus barbatus) was severe, unexpected, and greater for seedling than for clonal rubber. For undamaged trees, weeding frequency within the rubber-tree row had no significant effect, indicating that the major influence on rubber tree growth was interference from secondary forest regrowth between rows, operating both aboveand below-ground. In a farmer-managed, trial, vertebrate pest damage was the major influence on clonal rubber establishment, explaining almost 70% of the variation in rubber growth. The amount of labour invested in weeding was positively correlated with rubber growth. However, fanners generally decided to completely cut back the secondary forest regrowth between rows of rubber trees, including potentially valuable trees, rather than weeding within the rows and selectively pruning inter-row trees. Farmers considered that the inter-row vegetation may harbour vertebrate pests and compete with the clonal rubber, and they had access to fruits, firewood and non-timber forest products on other land. Thus, contrary to expectations, when offered clonal germplasm, these 'progressive' farmers opted to use plantation methods to protect what they considered a valuable asset suited to monoculture, rather than maintain the traditional multispecies strategy they use with local germplasm. Thus, although clonal rubber can technically be established in a 'jungle rubber'-like system (albeit with lower growth rates than achieved in plantations), not all farmers may be prepared to adopt this type of system.

Resource capture and utilisation were studied in two agroforestry systems at the International Centre for Research in Agroforestry (ICRAF) Research Station at Machakos, Kenya. The agroforestry systems examined contained two contrasting tree species, leucaena (Leucaena leucocephala (Lam.) de wit) and grevillea (Grevillea robusta), and the C3 and C4 crops, cowpea (Vigna unguiculata) and maize (Zea mays, Katumani composite). The leucaena-based trial was established in November 1989 and the trees were grown with ten maize crop rows on either side of a pruned hedgerow (HM) or unpruned tree row (LM). A sole maize control (SM) was also grown. Paired sets of treatments were irrigated to eliminate below-ground competition for water (HMI, LMI and SMI respectively). Interception of photosynthetically active radiation (PAR) by leucaena and maize was measured on a row-wise basis in all treatments at 7-10 day intervals using a sunfleck ceptometer. Sap flux was measured for the maize and both pruned and unpruned leucaena using heat balance gauges. Results are presented for the 1992 April-July rainy season. Total PAR interception was 30 % greater in LM and LMI than in the SM and SMI sole maize treatments. However, little more than 30 % of the light intercepted by the LM and LMI systems was captured by the crop component, and competition for light alone reduced maize yields by over 30 %. Total water uptake by the LM leucaena and maize comprised 60 % of the seasonal rainfall (237 mm) as compared to 30 % for sole maize. However, as for light interception, only 30 % of the water transpired in LM was used by the intercropped maize, and competition from the trees for soil water reduced maize yields at distances of over 6 m from the leucaena. The leucaena was more effective at resource capture, yet less efficient in resource utilisation since it exhibited a lower dry matter:radiation quotient and a lower transpired water:dry matter ratio than maize. Thus the leucaena in the agroforestry systems captured more of the resources that could have been used more effectively by the maize, causing the performance of the mixture to be sub-optimal; these results suggest that the two components would be best grown separately. Intensive monitoring of resource capture and use by trees and crops was subsequently transferred to the Complementarity In Resource Use on Sloping land trial (CIRUS). Although it had been intended to study both trials during the long rains of 1993, the leucaena trees were almost completely defoliated by psyllid (Heteropsylla cubana) infestation shortly before the onset of the rains: in subsequent seasons, CIRUS was studied in preference to the leucaena trial as the trees had only partially recovered. CIRUS was designed to investigate the effects of competition and the extent of complementarity between grevillea and associated crops using the following treatments; sole crops (Cg) of cowpea during the short rains and maize during the long rains, dispersed-planted trees with (CTd) and without crops (Td), and across (CTa) or on-contour-planted (CTc) tree rows with crops. Light interception and water use were monitored using a similar measurement regime to that employed in the leucaena trial. Results are presented for the 199213 and 1993/4 short rainy seasons; the failure of the 1993 long rains forced the abandonment of experimental measurements during this season. Light interception by the Td and CTd grevillea increased greatly between the two short rainy seasons. Thus, total seasonal interception of PAR was three times greater in sole cowpea than in sole grevillea during the 1992/3 short rains, but by the following short rainy season was over 50 % greater in the grevillea than in the cowpea. Cumulative interception of PAR by the CTd grevillea and cowpea combined was more than twice that of the sole cowpea and over 40 % greater than that for sole grevillea during the 1993/4 short rains. Experiments involving artificially imposed shade showed that there was no reduction in total above-ground dry matter production in cowpea until 75 % shading was imposed. To quantify the degree of below-ground complementarity in water use between grevillea and cowpea, sap flux was measured using heat balance gauges attached to the stems of young grevillea (10-18 months old), both before and after excavating the crop rooting zone (upper 60 cm of soil) around the stem base. The crop rooting zone was removed to establish the capability of the grevillea to extract water from deeper horizons. After excavation, the trees maintained sap fluxes of up to 85 % of the unexcavated values. During both short rains, soil evaporation was by far the largest component of the water balance in all treatments. However, continued extraction of water by the trees during the dry season greatly increased resource capture~ thus total water uptake was three times greater for the sole trees than for the sole crop when dry season water use was included. During the 1993/4 short rains, water use was greatest in the CTd treatment, in which 25 % of the total seasonal rainfall was transpired by the trees and crops. Although transpiration by the CTd trees exceeded interception losses, the latter may have had a greater effect on crop growth by reducing the total quantity of water available within the system. The existence of below-ground complementarity and the shade tolerance of the cowpea suggest that deep-rooted tree species and certain C3 crops may be combined successfully in the semi-arid tropics, but the sensitivity of crop yield to any reduction in water availability within the system demonstrates the need for caution when implementing such systems. The results obtained are discussed in relation to previous research on intercropping and agroforestry and their implications for the successful adoption of agroforestry systems in the semi-arid tropics.

The aim of the study was to establish whether clones could be selected for single or multipurpose products by conducting studies involving the evaluation of phenotypic characteristics and their influence on biomass production using Sesbania sesban (L.) provenances and clones. The study initially examined the extent of genetic variation in phenotypic characteristics and biomass production in S. sesban provenances at Maseno, in Kenya. The study showed that significant differences existed between provenances and that it was possible to select of outstanding individual trees in the best provenances for testing on different sites as clones. Significant allometric relationships were established between dry mass, and tree dimensions for the different tree components. Stem diameter at 0.15 m provided a reliable estimation of biomass in the provenances. The provenance repeatabilities (0.31-0.41) and potential genetic gain (40%) highlight the expected returns due to selection. Plant growth analysis results helped in understanding the growth of young S. sesban clones in the field at Maseno, particularly the distribution of biomass into components. Clones performed similarly in the initial stages of growth and differences were only detected when competition set in. Clone net assimilation ratios were found to be sensitive to moisture stress. Leaf area was found to be the major determinant of clonal differences and was a good indicator of plant growth and productivity. The results from the genetic variation and productivity study of S. sesban clones grown at Maseno, Kisii and Machakos revealed a differential response of the clones to different environmental conditions. Although there was lack of genotype by environmental interaction among clones, biomass production was higher at Maseno and Kisii than Machakos. S. sesban clones differed greatly in absolute biomass but showed similar percentage distribution of dry mass among the different tree components with branches being a major preferred sink.

Agroforestry, though old as man, is a relatively new concept in land and natural resource management. Agroforestry "offers a means of bringing the activities of rural people into greater harmony with the environment by developing a complementary association between trees and agricultural crops" (Ffolliott and Thames, 1983). The capabilities of a people to sustain a system is a fundamental knowledge that resource managers should be equipped with. This study specifically investigated on household labor allocation in three different agroforestry systems, to qualitatively determine whether agroforestry is a viable natural resource management alternative that provides a compromise to government interests of conserving the natural resources, and supplementing and/or providing for a people's needs; and to establish the capabilities of a people to sustain agroforestry by analyzing household labor allocation patterns. The study was conducted in the Northern Philippines and data was gathered summer of 1989. Primary data gathering techniques were utilized, as well as secondary data. Agroforestry was found to be a viable land and natural resource management alternative. However, while natural resources are being managed, certain considerations should be made on: historical antecedents that give rise to the manner by which agroforestry is practiced, existing land use practices, and human activities present in the area. Aside from biophysical constraints, household labor allocation largely explains the nature of the agroforestry system. Labor allocation in Barangay Ambassador is flexible, and is affected by the availability of household labor, and the nature of the activities engaged in by the households, as well as the importance attached to the cited activities.

This study reports the results of experiments on growth and physiology of an agricultural annual (French bean) and a young tree (poplar) in relation to limited soil water. Competition and complementarity between the species were evaluated in a model agroforestry experiment. The experiments were carried out in a greenhouse and growth cabinet with plants grown in pots containing sandy-loam compost. The species studied were Phaseolus vulgaris cv. Argus and Populus trichocarpa X P. deltoides cv. Raspalje. The main aim of the study was to characterise the responses of both species to different soil water supply regimes, shoot water supply by roots and chemical signalling from the roots in drying soil and to show how these responses could be used in the selection of suitable agroforestry for dry regions. Bean and poplar plants showed differential growth responses although both the species performed better in mixed stands than in monoculture when soil water was severely limited. Beanplants were more competitive than poplar, although both species showed complementarity in exploration for soil water. As the soil dried leaf water potential declined. Stomatal conductance of both species was more closely related to pre-dawn leaf water potential than to mid-day leaf water potential, indicating the importance of soil water status. Experiments with both vertically and horizontally divided root systems showed that bean and poplar plants with at least half of their root system in moist soil were able to maintain leaf water status as well as plants with all their root systems in moist soil. Furthermore, stomatal conductance and leaf expansion of both species were affected directly by soil drying independent of leaf water potential.

Agroforestry development programmes frequently rely on knowledge from a number of different sources. In particular, there is a growing recognition amongst development professionals of the value of augmenting partial scientific and professional understanding with the detailed knowledge held by local people. Taking advantage of the complementarity of local, scientific and professional knowledge demands the development of effective mechanisms for accessing, recording and evaluating knowledge on specified topics from each of these sources. The research described in this thesis developed a methodology for the acquisition, synthesis and storage of knowledge. The defining feature of the approach is the explicit representation of knowledge. This is achieved through the application of knowledge-based systems techniques. AKT2 (Agroforestry Knowledge Toolkit), a software toolkit developed in Prolog, an artificial intelligence programming language, provides the user with an environment for the creation, storage and exploration of large knowledge bases containing knowledge on a specified topic from a range of sources. The use of diagramming techniques, familiar to ecologists and resource managers through systems analysis, provides an intuitive and robust interface. This knowledge-based system drives incremental knowledge acquisition based on an iterative evaluation of the knowledge bases created. The iterative approach to knowledge acquisition provides a coherent, consistent and comprehensive, and therefore more useful, record of knowledge. Once created, knowledge bases can be maintained and updated as a record of current knowledge. Techniques for the exploration and evaluation of the knowledge base may be useful in : " giving research and extension staff access to a concise and flexible record of the current state of knowledge; " providing a resource and mechanisms for use in planning and prioritising research objectives; and " providing a resource and mechanisms for the generation of extension materials tailored to the needs of particular clients.

Because of the multiple values and services that trees deliver to society, agroforestry is increasingly interpreted as an agricultural innovation that can help to address challenges in modern agriculture. Despite its potential opportunities in Flanders, many farmers remain skeptical though, resulting in adoption rates that are lagging behind. Therefore the objective of this thesis is to gain a better understanding of the unfavorable environment for agroforestry adoption and development making use of a farming systems research approach (FSR). In Chapter 2 we explain FSR as our general research approach, which implies the consideration of three key characteristics, i.e. systems thinking, interdisciplinarity and a participatory approach. Taking into account the general FSR characteristics, Chapter 3, 4 and 5 “diagnose” the agroforestry implementation gap more in detail. In chapter 3, we gain some first insights by assessing farmers’ intentions to engage in agroforestry and by giving an overview of the current agroforestry acreage in Flanders. In Chapter 4, we use the Agricultural Innovation Systems concept as general framework to identify the different stakeholders and their respective roles, and to give an overview of the different merits and failures with respect to agroforestry development. Afterwards Chapter 5 elucidates the different perspectives that exist on agroforestry systems among Flemish stakeholders, and links them with general discourses on agriculture in Flanders. Diagnostic analyses were followed up by design exercises in Chapter 6, which looks into different instruments that may give economic incentives to farmers to adopt agroforestry. Taking into account the gathered insights, we present in the main discussion chapter five development pathways to further stimulate agroforestry adoption and development: (1) the science and technology pathway, which stands for investing in research, especially targeting the productivity and compatibility of agroforestry systems, and this in active collaboration with farmers; (2) the market and financial pathway, which implies the creation of market mechanisms in which landscape and biodiversity aspects are valued, while stimulating private investments and consumer demand; (3) the policy and institutional pathway, which aims for the creation of a fully-fledged legal landscape for agroforestry, which is clear and steadfast into the future, and which should be complemented with an attractive and effective subsidy program; (4) the educational and organizational pathway, which stimulates the use of multiple communication and education channels to inform the relevant actors and familiarize them with agroecological practices and their benefits for society; and (5) the social and behavioral pathway, which encourages strengthening the dialogue between influential groups to restore mutual confidence, build up common visions, and open up collaboration opportunities. Through further systemic, interdisciplinary and participatory research, the identified development pathways should be translated into concrete action plans to eliminate adoption barriers and close the agroforestry implementation gap in Flanders.
Doctorat en Sciences agronomiques et ingénierie biologique
info:eu-repo/semantics/nonPublished

The work reported here aimed to provide a comprehensive database of core information to support the development and validation of process-based models of resource capture and growth in semi-arid overstorey agroforestry systems. Intensive field studies were carried out in Kenya over a 30 month period and the results obtained were combined with data from a previous project to produce a dataset spanning a 4.5 year period. This dataset was then used to verify output from the HyPAR model. Allometric procedures developed from the pipe model theory (Lott et al., 1998) were used to estimate tree growth non-destructively throughout the observation period. Significant differences in tree size between the sole (Td) and dispersed agroforestry (CTd) treatments were established during the first 130 days after planting, probably because of competition with the associated crops. The above-ground biomass and trunk length and taper characteristics of the CTd trees remained inferior to those of Td trees throughout the observation period, seriously undermining the economic potential of this agroforestry system. The biomass and grain yield of CTd understorey crops were similar to the corresponding sole crops during the first three seasons, but were negligible in three of the final four seasons, with maize yields reaching 50 % of the equivalent sole crop values only when seasonal rainfall was well above average. This observation suggests that water availability was the primary limitation for CTd maize during the final seasons of the trial, a conclusion supported by the superior performance of maize grown under net enclosures which simulated tree shade in the absence of below-ground competition. Cowpea and maize were grown concurrently in two seasons to examine the impact of grevillea on C4 and C3 crops with contrasting responses to shade; biomass and grain yield were less affected in cowpea than in maize. The tree canopy in the dispersed agroforestry (CTd) treatment reduced the daily mean quantity of radiation incident upon the understorey crops by c.30 % during the final four growing seasons, although the discontinuous nature of the tree canopy caused substantial local variation in shading intensity. Seasonal mean fractional interception was greater for the combined canopies of the CTd treatment when soil moisture status was relatively high than for either of the sole canopies, suggesting the occurrence of spatial complementarity. Tree shade had a substantial moderating influence on meristem temperature since the mean diurnal temperature range was reduced from a maximum of 20°C in sole maize to 13 °C under the trees, and maximum meristem temperature was decreased by up to 6 °C relative to sole maize. However, the non-uniform shading provided by the trees caused substantial spatial variation in thermal time accumulation and hence crop development. Grevillea continued to grow during dry seasons and was therefore able to capture off-season rainfall which might otherwise have been lost from productive use. In addition, adaptation of heat balance gauges for use on grevillea roots (Lott et al., 1996) showed that substantial quantities of water could be extracted from deep-seated reserves below the crop rooting zone during dry periods, indicating the potential for spatial and temporal complementarity. However, transpiration by grevillea greatly exceeded rainfall during the dry season, rapidly depleting residual water supplies which might otherwise have been available for crop growth. In addition, approximately two thirds of the water used by the trees during cropping seasons was extracted from the soil surface horizons by lateral roots at distances of up to 2 m from the trunk. Thus, the potential for above and below-ground complementarity may be seriously undermined by the extensive capture of water by tree roots from the crop rooting zone. Comparison of output from the HyPAR model against the observed results provided information pertinent to future model development. The model proved to be insufficiently flexible for end-users wishing to simulate the growth of different crops during the same simulation cycle, or to use model output to aid management decisions such as the timing of pruning. The allometric procedures used by the model to estimate canopy size from trunk diameter at breast height also proved incapable of accounting for reductions in canopy size resulting from pruning. Estimates of tree height are rounded to the nearest metre within the model, representing a potentially serious loss of resolution when annual increments often do not exceed 2 m. In addition, the numerous parameters required by the model would force most end-users to rely heavily on published information, potentially undermining the reliability of simulations.

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A mudança climática global tem sido atribuída ao aumento da concentração de gases de efeito estufa na atmosfera, especialmente o dióxido de carbono (CO2), como resultado das atividades humanas. Para atenuar esse efeito, existe um esforço global em reduzir as emissões de CO2 e desenvolver tecnologias para remover parte desse gás da atmosfera. A maneira mais simples e natural para remover o CO2 da atmosfera é realizada pelas plantas através da fotossíntese. Este processo remove o carbono da atmosfera formando biomassa vegetal, a qual mais tarde será depositada no solo, maior reservatório de carbono (2500 GtC) na biosfera terrestre. O balanço de carbono no solo é resultado da deposição de biomassa vegetal e perda de carbono, especialmente como CO2. Portanto, o solo, no ciclo global do carbono, pode atuar como fonte ou dreno de carbono da atmosfera. Para melhor compreensão do papel do solo no ciclo do carbono não é suficiente conhecer apenas a quantidade de carbono que determinadas espécies de plantas depositam no solo, mas também como esse carbono é liberado de volta para a atmosfera. O CO2 é liberado (efluxo de CO2 do solo) a partir de respiração do solo, a maior fonte de CO2 da biosfera terrestre. O efluxo de CO2 do solo é um processo complexo que depende das características biológicas e físicas do solo, especialmente das condições de temperatura e umidade do solo. No entanto, o tipo de vegetação e as práticas agrícolas podem ser os principais componentes que controlam o efluxo de CO2 do solo em agroecossistemas, porque influenciam as características biológicas e físicas do solo e regulam as condições de temperatura e umidade do solo. Nos sistemas agroflorestais as árvores aportam matéria orgânica no solo e o protegem contra a radiação solar direta, influenciando assim o efluxo de CO2 do solo. O objetivo geral deste estudo foi compreender como a copa das árvores, em sistemas agroflorestais com café, afetam o efluxo de CO2 do solo e quais os fatores controladores deste processo em comparação com café a pleno sol. Para isso avaliou-se o efluxo de CO2 do solo (in situ), em sistemas agroflorestais com café e em sistemas com café a pleno sol em três propriedades de agricultores familiares na Zona da Mata de Minas Gerais, Brasil. O aumento nos níveis de cobertura da copa das árvores resultou no aumento da umidade do solo e na diminuição da temperatura do ar e do solo a 5 e 10 cm de profundidade. O efeito das árvores no microclima não afetou a média diária de efluxo de CO2 do solo entre os sistemas agroflorestais e a pleno sol, mas contribuiu para que a dinâmica das emissões diárias fosse diferente entre os sistemas. No sistema agroflorestal o efluxo de CO2 do solo foi mais estável durante o dia com menor variação entre o período de 08:00-10:00h e 12:00-14:00h e maior variação espacial do que no sistema a pleno sol. No sistema agroflorestal o efluxo de CO2 foi explicado principalmente por variações na quantidade de nitrogênio total e carbono lábil e no sistema a pleno solo pela temperatura do solo, especialmente a 10 cm de profundidade. A análise de componetes principais mostrou que em geral o efluxo de CO2 do solo correlacionou positivamente com a temperatura do solo a 5 e 10 cm de profundidade e negativamente com a umidade do solo. Em conclusão, as árvores em sistemas agroflorestais de café trouxeram maior estabilidade para o microclima e para o efluxo de CO2 do solo comparado com sistemas a pleno sol.
The global climate change has been attributed to increasing greenhouse gas concentration, especially Carbon Dioxide (CO2) in atmosphere as result of human activities. To mitigate this effect, there is a global effort to reduce CO2 emissions and develop technologies to remove part of this gas from the atmosphere. The most simple and natural way to remove CO2 from atmosphere is carried out by plants through photosynthesis. This process removes carbon from atmosphere creating vegetal biomass, which later will be deposited in soil, the biggest reservoir of carbon in the terrestrial biosphere (2500 GtC). The balance of carbon in the soil is the result of input of vegetal biomass and the output of carbon, especially as CO2. Therefore, the soil, in the Global Carbon Cycle, acts either as source or as a sink of carbon from the atmosphere. To better understand the role of soil in Carbon Cycle and to it become sink of CO2 it is not enough to know the carbon that particular plant species can deposit in the soil, but also how this carbon is released back to atmosphere. The CO2 is released from soil (also called soil CO2 efflux) mainly from soil respiration, which is the biggest source of CO2 from terrestrial biosphere. Soil CO2 efflux is a complex process that depends on the soil biological and physical characteristics and especially on the soil temperature and moisture conditions. However, the vegetation type and the agricultural practices may be the main components to control the soil CO2 efflux in agroecosystems, because they influence the soil biological and physical characteristics and control the soil temperature and moisture conditions. Agroforestry coffee management increases the amount of organic matter residue and the canopy’s trees protect the soil against the directly solar radiation, thus, affecting the soil CO2 efflux. The general objective of this study it was to understand how the canopy’s trees in agroforestry and full-sun coffee systems affect the soil CO2 efflux and which factors control it. To this end we evaluated the soil CO2 efflux (in situ) in agroforestry and full-sun coffee systems in three different farms in Zona da Mata of Minas Gerais, Brazil. The increase in canopy cover levels from trees leads to increase soil moisture and decrease air and soil temperature at 5 and 10 cm depth. The effect of trees on microclimate did not affect the daily average of soil CO2 efflux between agroforestry and full-sun coffee systems, but they showed different daily emission dynamics. In agroforestry system the soil CO2 efflux was more stable during the day, presenting less variation from morning to midday and higher spatial variation than the full-sun system. In agroforestry system the variation of soil CO2 efflux was explained mainly by total nitrogen and labile carbon and in full- sun system by soil temperature at 10 cm depth. The principal components analysis shows that in general the soil CO2 efflux was positively correlated with soil temperature at 5 and 10 cm depths and negatively correlated with soil moisture. In conclusion, the trees in agroforestry coffee systems promoted stability to microclimate and soil CO2 efflux compared to Full-Sun systems.

Informal agroforestry is a traditional practice in Solomon Islands, mostly intercropping food crops with fruit trees. Agroforestry systems that intercrop food crops with rows of hardwood species for the purposes of timber production have not been practiced. In response to the common problem that growers of valuable hardwood species such as teak (Tectona grandis) are reluctant to thin their trees, the Australian Centre for International Agricultural Research (ACIAR) established project FST/2007/020 to develop novel silvicultural systems to overcome this problem. Flueggea flexuosa (flueggea) is a local hardwood species that is widely utilized for housing and fencing applications. The project team established several agroforestry trials testing the hypothesis that teak and flueggea could be successfully grown together with the local tree being progressively harvested for local use, effectively thinning the plantation and allowing the teak to develop through to harvestable size. The trees could be intercropped with food crops allowing for multiple land use and income generating opportunities whilst the trees grow through to maturity. The model was based on the assumption that trees and crops, when properly managed, complement each other rather than compete in the capture and efficient use of available growth resources. This system is a hybrid of the informal agroforestry traditionally practiced in Solomon Islands and the silvicultural management techniques applied to production forestry. However, teak and flueggea have not been previously grown together under an agroforestry regime and little is known of the species interaction or of the effect of growing different food and cash crops in the interrow. Traditional practices for growing food crops in Solomon Islands begin with forest clearance and burning of debris, a slash and burn system. Mounds are made using man-made hoes or picks to give crops better growing spot away from competing weeds and surface water flow during rainy seasons. Most root crops and vegetables are planted in their own blocks and kept separate from other crops. Mixing of food crops is not a usual practice in most parts of the Solomon Islands. Other crops and trees are usually planted at the boundaries of each crop’s patch or along the boundary. Most food crops reach harvesting age after 3 months. When crops are harvested, the whole plant is uprooted, plant parts and debris are piled at a location and are burnt when dry. Where the area available for gardening area is large, the harvested plot is left to fallow but if the available area is small, crops are replanted straight after harvest, leaving no time for the soil to be replenished with nutrients through decomposition of plant materials. Amongst several silvicultural trials established in Solomon Islands, this study focuses on trials established at Ringgi and Poitete which are located at the southern and northern parts of Kolombangara Island in Western Province. These silvicultural trials were established for the purpose of examining the effect of stocking rate and species mix on teak and flueggea growth and on their potential influence over the hybrid agroforestry system. Two mixed species spacing trials and one hybrid agroforestry trial of teak and flueggea were established to test the hybrid model. The two main mixed species spacing trials have 5 treatments with 4 replicates each, treatments are a combination of stocking rate and species mix. The five different treatments include teak being grown as a monoculture (Treatment 1); and then in rows interspersed with 2 rows of flueggea at different stocking rates (Treatments 2, 3, and 4); and alternating rows of teak and flueggea at standard spacing (Treatment 5). The hybrid agroforestry trial was based on the standard 4 x 3 m spacing (Treatment 5) and further intercropped with food crops. Only Treatment 3 (4 x4m) and Treatment 4 (4 x 6m) have wider planting spaces. Standard stocking is 833 stems per hectare for Treatments 1, 2 and 5, and 625 and 416 stems per hectare for Treatments 3 and 4. This research examined the interactions occurring between teak and flueggea, and between teak, flueggea and food crops grown in the inter-row with respect to competition for nitrogen (N), light and water, resource access, changes in system interactions with the development of the canopy, nutrient loss and issues of sustainability related to harvesting of food crops, biogeochemical cycling of carbon (C) and N, root architecture and growth and yield. Total carbon (TC), total nitrogen (TN) and stable isotope δ13C and δ15N, and 15N-labelled tracer were analyzed using field sampled soil, foliage, branch, stem, root and litterfall from the stands to examine soil nutrient uptake, biomass content and cycling as a result of the intraspecific and interspecific interactions with relation to tree growth and productivity of the hybrid system over time and space. Root architecture, tree mean total height (THt) and diameter at breast height (DBH) were measured and assessed over the study period. We investigated the competition between teak and flueggea for N using a 15N-labelled tracer in a field trial in a 2 year old and a 4 year old mixed species stand. The study also reports the acquisition and allocation of TC and C isotope composition (δ13C) in different tree components of teak and flueggea. Seven pairs of trees, one of each species, were isolated using an impermeable membrane 60 cm deep and 15N-labelled tracer was applied to the soil surface. The first four plots were sampled for a period of 18 months and the age of the trees at final excavation was 4 years. The final three plots were sampled for 12 months and the age of the trees at final excavation was 2 years. Each tree was measured, felled and roots excavated, divided into the components: roots, stem, branch and foliage, and then weighed for biomass, samples of each component were oven dried at 60° C to constant weight, ground to a fine powder and analysed for TN, TC, 15N enrichment, and δ13C. There was no significant difference in component 15N enrichment between teak and flueggea at both ages, suggesting that there could be equal uptake of added 15N-labelled tracer by both species. The 15N -labelled tracer concentration was greater in the foliage followed by the root, stem and branch for teak and flueggea. However, stem had significantly greater biomass and therefore had greater 15N enrichment mass (kg) than other components of teak in the 2 years trial and with teak and flueggea at 4 years trial. Approximately 55 % of added 15N tracer was recovered in the 4 years trial and 43 % was recovered in the 2 years trial, suggesting that higher uptake is possible with well-established root structure with age. Although teak had significant growth, 15N tracer uptake and enrichment were not statistically different to those of flueggea which may mean that competition in growth resources was still at minimum stage and growth rates were species specific. TN was not significantly different between teak and flueggea components at age 2 and 4 years and may indicate equal access to available N belowground and with similar allocations. TC was not significantly different between components of teak and flueggea in either age and may indicate equal access to atmospheric C and similar allocations of photosynthates. Higher δ13C in teak components than those of flueggea indicated that teak has higher water use efficiency per kg of tree and does not discriminate against 13C as strongly as flueggea during photosynthesis. Similar 13C values in tree components within the species may be the result of subsequent partitioning of the photosynthates synthesized during photosynthesis. The litter production and C and N cycling in both teak monoculture and teak and flueggea mixed species plantings in the two trials were studied over 18 months period. Leaf litter samples were collected monthly from the five treatments. Monthly litterfall production ranged from 250.51 to 541.61 kg ha-1 depending on treatment and trial. Treatment 1 produced significantly higher total litter than Treatment 4 at Ringgi but this difference will have been due to stocking rates. When based on individual tree productivity, teak in Treatment 4 at both trials produced significantly higher litter per tree than the teak in Treatments 3, 2, 5 and 1 while there was no significant difference with flueggea productivity. Although teak and flueggea TC and TN, and δ13C and δ15N varied over the study period, their mean values were not statistically different except for teak in T4 having significantly lower values at Ringgi. Teak and flueggea C/N ratios were not statistically different at both trials except for flueggea in Treatment 2 at Ringgi which was significantly higher. The highest annual TC and TN returned to the soil from total litterfall were observed in Treatment 1 followed by Treatments 3, 5, 2 and 4 for Ringgi. The highest at Poitete was Treatment 5 followed by Treatments 1, 3, 2 and 4. When comparing each treatment and using individual tree productivity, Treatment 4 produced and returned the significantly highest litter and nutrient than Treatments 3, 2, 5 and 1. Overall, individual tree productivity demonstrated that mixed species stands have significant potential for cycling higher rates of C and N than monoculture teak stand, therefore establishment of mixed species stands especially using the stocking rates of Treatment 3 and Treatment 4 is recommended as a practical measure in forest rehabilitation and agroforestry systems to realize sustainable development of community forestry in the Solomon Islands. The spatial distribution of the root systems of teak and flueggea were examined by excavating pairs of trees of each species that had been grown in isolation plots for 2 (3 pairs) and 4 (4 pairs) years. Additional trees grown without a barrier were partly excavated to ensure that the effect of the barrier on root architecture was not significant. The root architecture of both species had similar patterns of development but showed a different topology and distribution. Teak had extensive horizontal and vertical roots and occupied a larger portion of the soil volume than flueggea. Both species had similar root biomass increment of 87 % between 2 and 4 years and roots made up 20-22 % of total tree biomass at both ages. Teak and flueggea roots occupied different depths within the soil volume, which would promote nutrient uptake efficiency and therefore minimize competition. The study evaluated the effects of stocking rate and species mix on early growth of teak in a mixed species system. Intercropping with flueggea promoted diameter, height and form of teak. Teak diameter and basal area growth significantly increased with wider planting spacing though height was not statistically different to teak in single-species stands. Intercropping with flueggea resulted in teak developing smaller branches which facilitated a self-pruning habit that promoted clear wood production. Differences in teak height between all treatments were not significant though it is interesting to note that sixty months after planting, teak in T1 at Ringgi and teak in T5 at Poitete had the greatest height as had Flueggea in T5 at Ringgi though again differences in height of flueggea was not significantly throughout the treatments. Diameter and basal area were greatest at the lower stocking than at the higher stocking for teak and flueggea. Teak of T4 had the significant diameter and basal area growth than other treatments at age 60 months. Teak form was best at the pure and mixed species stands due to self-pruning while larger crown and big branches occurred at lower stocking rates. While this can be corrected with timely silviculture, a 4 x 3 m spacing would seem to optimise the benefits of higher stocking and lower maintenance. Overall, mixed species and agroforestry systems promoted reduction and delay of competition for growth resources in the early phase of the systems compared to monocultures. Both single and mixed species systems promoted similar C and N cycling in the plantation establishment phase. Growth in basal area was significantly higher at the mixed species stands at the lowest stocking rate, which also enable longer period of intercropping of food crops. However, as the present investigation was confined to the first 5 years, which is considered as establishment phase for teak, more studies are needed as the systems mature to fully understand the systems development and interactions to maturity.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Natural Sciences
Science, Environment, Engineering and Technology
Full Text

The future of food production contains some challenges. The production needs to increase in order to feed a growing population, but at the same time there is an increased need to transi- tion to more sustainable ways of cultivation. This can be a challenge since increased intensity and sustainability is not always compatible. Agroforestry systems have shown potential as sustainable food production system in previous research. The area where this study was con- ducted, Haraa in Babati District, has a long history of agroforestry. The aim of this study was to answer what resources agroforestry farmers used to manage their farms, to determine if the agroforestry systems could be regarded as sustainable. Circular economy was used as a theo- retical framework and resource flow as an analytical tool. This study investigated how the resource flow looked like on six agroforestry farms in a Haraa, a village in Tanzania. The empirical data was gathered with semi-structured interviews from 8 informants. The analysis showed that the farmers were dependent on few external resources and could produce or pre- form most of the needed resources inside their own system. The farms had a circular flow to a large extent, but some of the farms have room for improvement in the management regarding sustainability.

Deutscher Akademischer Austausch Dienst
For thousands of years, people have practiced different forms of agriculture, based mostly on the handling of materials available in their own land. Among these, we highlight the organic origin, that allow an improvement of soil quality and increased crop production. In this context, this dissertation presents a study of five years, from 2008 to 2012, of an Agroforestry System (AFS) for growing corn and beans intercropped with gliricidia and cashews, in conditions of northern coast of CearÃ. The (AFS), had four treatments: Testimony (A), under normal conditions the AFS; Dung (B), with the addition of 116 grams of sheep dung in the pit of corn and beans at planting time; Bagana (C), with addition of 16 tons of carnauba straw on the soil as mulch; and Dung + Bagana (D), which is a combination of treatments B and C. In addition to the experimental treatments, 10 local farmers were interviewed to develop the treatment (T) Regional Testimony (local production system). Two analyzes were performed comparing this 5 treatments: Productivity of the system and its Economic analysis. It was concluded that the AFS assists in fixing agriculture, avoiding the opening of new areas for cultivation, having succeeded to higher production levels than the obtained by local itinerant cultivation. Regarding the productivity, was noticed an increasing pattern from treatment T (lower middle), through A, to the D, which has always had the highest average productivity besides showing greater resilience to the effects of drought. The T and A treatments were not economically viable, with negative indicators. Whereas the B, C and D treatments proved feasible economically and financially, with the best indicators in treatment D. For this set of analyzes, the proposed AFS, especially the treatment D, presents itself as the most advantageous for the exploitation of agriculture in studied conditions.
Durante milhares de anos, diferentes povos tÃm praticado uma agricultura baseada no manejo dos materiais disponÃveis nas suas prÃprias terras. Dentre esses, podemos destacar os de origem orgÃnica, que possibilitam uma melhoria da qualidade do solo e um aumento da produtividade vegetal. Nesse contexto, esta dissertaÃÃo apresenta um estudo sobre 5 anos, de 2008 à 2012, de um Sistema Agroflorestal (SAF) para cultivo de milho e feijÃo, consorciados com gliricÃdia e caju, nas condiÃÃes edafoclimÃticas do litoral norte do CearÃ. O referido SAF, apresentou 4 tratamentos: Testemunho (A), em condiÃÃes normais do SAF; Esterco (B), com adiÃÃo de 116 gramas de esterco de ovelha na cova do milho e do feijÃo no momento do plantio; Bagana (C), com adiÃÃo de 16 toneladas de bagana de carnaÃba sobre o solo como cobertura morta; e o Esterco + Bagana (D), que à uma combinaÃÃo dos tratamentos B e C. AlÃm dos tratamentos experimentais, foram entrevistados 10 agricultores locais para elaborar o tratamento (T) Testemunho Regional (sistema de produÃÃo local). Foram realizados duas anÃlises comparando os 5 tratamentos: Produtividade do sistema e sua AnÃlise econÃmica. Concluiu-se que o SAF auxilia na fixaÃÃo da agricultura, evitando a abertura de novas Ãreas para cultivo, pois conseguiu nÃveis produtivos superiores aos obtidos pela agricultura itinerante local. Em relaÃÃo à produtividade, percebeu-se um padrÃo crescente desde o tratamento T (menores mÃdias), passando pelo A, atà o D, que apresentou sempre as maiores mÃdias de produtividade alÃm de apresentar uma maior resiliÃncia aos efeitos da seca. Os tratamentos T e A nÃo foram economicamente viÃveis, apresentando indicadores negativos. Jà os tratamentos B, C e D mostraram-se viÃvel econÃmica e financeiramente, com os melhores indicadores no tratamento D. Por esse conjunto de anÃlises, o SAF proposto, principalmente o tratamento D, se apresenta como o mais vantajoso para exploraÃÃo da agropecuÃria nas condiÃÃes estudadas.

L'agroforesterie est un système dynamique d'aménagement écologique des ressources naturelles renouvelables, qui en intégrant les espèces ligneuses aux champs agricoles, fermes et autres paysages, diversifie, augmente la production et engendre des bénéfices socioéconomiques et environnementaux. En tant que solution pour la fourniture des services écosystémiques, son application à la restauration des écosystèmes dégradés, endommagés ou détruits devient très importante. Les terres dégradées, endommagées ou détruites (3-D) par l’exploitation minière sont caractérisées par un sol de faible fertilité et parfois des niveaux élevés des contaminants. Ces conditions les rendent difficile l'obtention d'un avantage à court terme de l'agroforesterie en comparaison aux terres arables, mais sa principale fonction restaurative consistant à rétablir les services écosystémiques et à accroître la résilience peut être bénéfique à long terme. Le défi consiste à développer la meilleure stratégie pour accélérer la productivité des plantes tout en améliorant le sol et l’écosystème grâce à une combinaison des techniques d’ingénierie écologique pour la biorestauration des milieux miniers. Nous explorons ici le mélange de plantes, d’inoculation microbienne et d’amendement en biochar, dans un système agroforestier ligneux-herbacé. L’objectif est de trouver le meilleur scénario de biorestauration à partir des effets combinés de mélange de plantes et d’autres facteurs écologiques connexes. Des recherches antérieures sur l'agroforesterie et la restauration ont été révisées à travers le monde entier, y compris l’application du concept agroforestier en biorestauration des terres post-minières. La stratégie de restauration connue dans un milieu donné ne constitue pas une solution universelle. Ainsi, l'identification de tout aspect important des travaux antérieurs sur la restauration et l'agroforesterie est cruciale. La stratégie de mélange des plantes est un facteur important dans les processus de succession. Dans cette recherche, nous avons appliqué le concept de parcelles de Nelder modifié pour la combinaison d'espèces de plantes dans une expérience en serre sur les stériles et les résidus fins afin d'explorer l'interaction au début de la plantation. Nous avons aussi appliqué l’inoculum microbien et le biochar sur le mélange de plantes dans des essais en serre et sur le terrain sur les stériles et les résidus fins comme matériau de sol d’un site post-extraction de l’or. La performance de la co-plantation de quatre espèces ligneuses (Alnus viridis (Chaix) DC. ssp. crispa (Aiton) Turrill, Picea glauca (Moench) Voss, Populus tremuloides Michx. et Salix arbusculoides Andersson) avec les les espèces de plantes herbacées (Avena sativa L., Festuca rubra L. et Trifolium repens L.) a été évaluée. Le mélange de plantes est un principe très important dans les pratiques de restauration, étant donné son rôle connu pour augmenter la biodiversité et la diversité fonctionnelle dans le système écologique durable. Bien que la stratégie de mélange ait été rarement explorée, nous avons constaté que la combinaison des espèces avait un effet neutre (ni avantages, ni inconvénients) par rapport à une seule espèce dans l’expérience de parcelles de Nelder. En même temps, l'effet positif de la densité suggérait que l'amélioration du microclimat avait joué un rôle dans la croissance précoce des plantations. L'essai sur le terrain confirme l'effet positif de la modification du microclimat sur la productivité des plantes lorsque la densité de plantation est élevée. Le compromis sur la concurrence des plantes a montré que la densité la plus élevée ne constitue pas nécessairement une condition optimale pour la productivité des plantes. L'effet d'interaction du biochar et du traitement d'inoculation montre l'intérêt de ce traitement, mais l'impact varie selon la densité de plantation. La densité de plantation a été démontrée comme le facteur le plus important pour générer l'effet positif net. Nous suggérons que le mécanisme était corrélé à l'amélioration du microclimat par la conservation de l'eau des plantes du sol et l'amélioration de l'activité microbienne par rapport à la modification de la température du sol. Par conséquent, mettre l'accent sur l'amélioration du microclimat, ainsi que sur d'autres facteurs combinés, y compris l'inoculation microbienne et l'amendement du biochar, est très important pour accélérer les processus de restauration.
Agroforestry is a dynamic system of ecological management of renewable natural resources, which by integrating woody species into agricultural fields, farms and other landscapes, diversifies and sustains production for increased socio-economic and environmental benefits. As a solution for the provision of ecosystem services, its application to the restoration of degraded damaged, or destroyed ecosystems becomes very important. Degraded, damaged, or destroyed (3-D) lands by mining is characterized by low fertility soil and sometimes high levels of contaminants. These conditions make them difficult to obtain a short-term advantage from agroforestry compared to arable lands, but its main restorative function of restoring ecosystem services and increasing resilience can be beneficial in the long term. The challenge is to develop the best strategy to accelerate plant productivity while improving the soil and the ecosystem through a combination of ecological engineering techniques for bioremediation of mining areas. Here we explore the mixture of plants, microbial inoculation, and biochar amendment, in a woody-herbaceous agroforestry system. The goal is to find the best bioremediation scenario from the combined effects of mixing plants and other related ecological factors. Previous research on agroforestry and restoration has been reviewed worldwide, including the application of the agroforestry concept in bioremediation of post-mining land area. The known restoration strategy in a given environment is not a universal solution. Thus, the identification of any important aspect of previous work on restoration and agroforestry is crucial. The strategy of mixing plants is an important factor in the successional process. But a statistical accounting of plant-plant interactions and adaptation to multi-species conditions is hard to achieve in field experiments; trials under controlled conditions can distinguish effects of planting density and species interactions in the early stages of plant establishment. In this research, we applied the concept of modified Nelder plots for the combination of plant species in a greenhouse experiment on waste rock and fine tailing to explore the interaction at the start of planting. We also applied microbial inoculum and biochar to the plant mixture in greenhouse and field tests on waste rock and fine tailing as soil material on a post-gold mining site. The performance of the co-planting of four woody species: green alder (Alnus viridis (Chaix) DC. ssp. crispa (Aiton) Turrill); white spruce (Picea glauca (Moench) Voss); trembling aspen (Populus tremuloides Michaux); and littletree willow (Salix arbusculoides Andersson) with the herbaceous plant species: oat (Avena sativa L.); red fescue (Festuca rubra L.) and white clover (Trifolium repens L.) was evaluated. Mixing plants is a very important principle in restoration practices, given its known role to increase biodiversity and functional diversity in the sustainable ecological system. Although the plant mixing strategy has been rarely explored, we have found no mixture provided advantages for both species in paired combinations. At the same time, the positive effect of the density on plant growth suggested that the microclimate improvement had played a role in the early growth of the plantations. The field trial confirms the positive effect of the microclimate modification on plant productivity in higher planting density. The trade-off on plant competition has shown, however, that the highest density does not necessarily show an optimal condition for plant productivity. The interaction effect of biochar and inoculation treatment shows the benefit of this treatment, although the impact varies according to the density of planting. The plantation density was shown as the most important factor in generating the net positive effect. We suggest that the mechanism was correlated with the microclimate improvement through soil plant water conservation and microbial activity enhancement over soil temperature modification. Hence, putting emphasis on microclimate improvement, along with other combined factors including microbial inoculation and biochar amendment is very important for accelerating the restoration processes

This study, conducted in Indian Western Himalaya, investigated factors affecting tree growing in traditional agroforestry systems and the perspective of women and forestry staff towards agroforestry. Many physical, socio-economic, forest resource use and perceptional factors influenced tree growing. Forestry related factors were found through logistic regression to be weak determinants of tree growing. Farm size, traditional farm fencing agroclimatic zone and soil fertility were the important physical determinants. Worship of holy trees, importance of tree growing for future generations, mobility of head of household and family literacy were important social determinants. Agricultural production, off-farm income and restriction on grazing on-farm were important economic factors. The key forest resource use factors affecting agroforestry adoption were previous participation in forestry programmes, primary source of fuelwood, extent of natural regeneration and distance travelled to collect fuelwood. The perception about restriction on felling trees from their own farm and attitude towards agroforestry were key perceptional factors. Women’s decision to grow trees was nested within the overall household’s decision whether to grow trees. In tree-grower households, women grew trees to meet their own and overall household interest. In contrast to expectations, women preferred growing trees for fruits over fuelwood. The dilemma of foresters in properly identifying the issues related to on-farm tree growing was due to their conflicting roles as members of the local society on the one hand and foresters on the other. From the perspective the restriction on felling farm trees and selling them in the market was the most important constraint on tree growing. They preferred provision on incentives for tree growing as the most important motivator. Agroforestry training was concentrated on nursery and plantation management but they now recognise they need training in extension and agricultural aspects of agroforestry. Efforts to encourage tree growing should not merely consider on-farm tree growing in isolation of on-farm and off-farm affecting livelihoods of farmers.

The productivity of two spatial arrangements of a perennial pigeonpea/groundnut agroforestry system was examined in relation to the capture and use of light and water and alterations in microclimatic conditions. Line planted (5.4 m alleys) and dispersed arrangements (1.8 x 1.2 m spacing) of pigeonpea were compared, using populations of 0.5 plants m2 for pigeonpea and 33 plants m2 (0.3 x 0.1 m spacing) for groundnut in both treatments. Sole pigeonpea and groundnut treatments were included for comparison. The experiment was conducted between July 1989 and March 1991 on a 0.6 ha plot of Alfisol at ICRISAT Center, Andhra Pradesh, India, using a randomised block design with four replications. The first groundnut harvest took place in October 1989, while pigeonpea was harvested for grain and fodder in January 1990, and was cut to a height of 0.5 m during the 1990 dry season and again in August 1990 after a second groundnut crop was sown. The second groundnut harvest took place in November 1990 and the final pigeonpea grain harvest was in January 1991. Light interception, soil and leaf temperatures and saturation deficit were continuously monitored in all treatments and at various distances from the pigeonpea in the line and dispersed treatments, whilst windspeed was monitored at a single location in each treatment. Regular destructive samples of groundnut were used to establish effects on growth and development and the results were considered in relation to the concurrent physical measurements to determine the environmental factors influencing productivity. In order to establish a water balance, rainfall records were maintained, runoff plots were installed and soil moisture content was measured regularly throughout the drying cycle. Transpiration by pigeonpea was monitored using a heat balance technique, while transpiration by groundnut and soil surface evaporation were estimated from micrometeorological data. As pigeonpea is initially slow growing, there was little reduction in groundnut yield in either the line or dispersed treatments in 1989 and there was a slight intercrop advantage in overall biomass production when expressed in the terms of the land equivalent ratios. In 1990, groundnut pod yield was reduced by 20 and 44 % in the line and dispersed treatments relative to the sole crop, despite substantial increases in the light conversion coefficient for the shaded groundnut. The lower pod yield resulted from the delayed onset of pod initiation and a slower rate of development, and was mainly due the effects of shading by the pigeonpea canopy, although mild water stress may have been a minor contributory factor. The small reductions in saturation deficit and soil and leaf temperatures experienced by the shaded groundnut had a negligible effect on growth and development. There was a considerable increase in overall biomass production in the line and dispersed treatments as compared with 1989 due to rapid pigeonpea growth, which reflected an increase in overall resource use rather than in the light conversion coefficient or water use ratios of the systems. The influence of spatial arrangement on the growth and productivity of pigeonpea became apparent after the 1990 dry season. Biomass production by pigeonpea in the dispersed treatment was approximately double that of the line planting between August 1990 and January 1991. This was entirely due to increased transpiration by the dispersed pigeonpea as a result of greater utilisation of stored soil moisture and reduced losses by surface evaporation and deep drainage. There was no difference in the water use ratio. To examine further the mechanisms responsible for the differences in productivity and water use by the line and dispersed pigeonpea, trench profile methodology was used to examine the root systems in December 1990. The root system of the dispersed pigeonpea was distributed over the entire 2.0 m depth x 2.7 m width exposed soil profile, whilst that of the line arrangement occupied no more than 50 % of the same area. The results of this work are discussed in relation to previous studies of resource use and productivity in intercropping and agroforestry systems, and possible applications and future developments are considered. Finally, the major physical and socioeconomic factors determining the potential of perennial pigeonpea/groundnut agroforestry systems for adoption by farmers in semi-arid India are discussed.

Increasing demand for timber, fuelwood and other forest products has outstripped production in many areas of the semi-arid tropics, leading to deforestation and land degradation resulting from erosion and nutrient depletion. Agroforestry offers the potential to provide forest products, improve productivity and reduce soil erosion and environmental degradation. However, as previous reports have shown that competition between trees and crops for water in semi-arid areas adversely affects crop yields, attention has turned towards studies of the existing practice of boundary planting, where low tree planting densities and the associated benefits of land demarcation and soil stabilisation increase the viability of incorporating trees into crop land. The aim is to select and manage tree species in ways that limit their negative effect on crop yields and improve the overall value of the system. The present study was carried out at Machakos (1° 33' S, 37° 14' E, altitude 1660 m) in the Kenyan highlands, where the bi-modal annual rainfall of c. 740 mm is divided approximately equally between two rainy seasons (short rains, October-February, long rains, March July). The experiment was set up in April 1993 to examine the influence of tree/crop interactions on system productivity. Each 18 x 18 m plot, except for the sole crop plots, contained a central row of trees planted at 1 m spacing. Four overstorey agroforestry treatments were examined between March 1996 and March 1998; these included two indigenous species, Croton megalocarpus and Melia volkensii, and two exotic species from Central America, Senna spectabilis and Gliricidia sepium. Beans (Phaseolusulgaris) and maize (Zea mays) were grown during the short and long rains respectively. M. volkensii and S. Spectabilis exhibited similar leafing phenology patterns, losing almost all leaf cover during the long dry season (July-October) and flushing before the ensuing rains. During the short dry season, S. spectabilis lost few leaves, whilst M. volkensii lost some leaves before flushing prior to the onset of the long rains. M. volkensii lost a large proportion of its leaf cover during the 1997/98 short rains due to the unusually high soil moisture content. C. megalocarpus although predominantly evergreen, lost a large proportion of its leaves during dry periods, whereas leaf area increased rapidly under wetter conditions. G. sepium had one annual period of low leaf cover during the long dry season and did not regain full leaf cover until mid-way through the short rains. The three-dimensional model of canopy photosynthesis and transpiration, MAESTRA, was parameterised for C. megalocarpus and M. volkensii using existing models to describe the response of photosynthesis to light and temperature and stomatal responses to light and vapour pressure deficit. The photosynthesis model fitted the experimental data well, but stomatal conductance in C. megalocarpus, although showing responses to light and vapour pressure deficit, was not closely correlated with ambient environmental conditions. M. volkensii had higher leaf area than C. megalocarpus for most of the 18 month simulation period, comprising three rainy and three dry seasons; modelled assimilation for this period was 49 % greater in M. volkensii, while canopy water use efficiency and transpiration were respectively 35 and 11 % higher. These differences accounted for the more rapid growth rate and greater competition with adjacent crops associated with M. w1kenrii relative to C. megalocarpus. Above-ground woody biomass production was greatest in M. volkensii, followed by S. spectabilis, C. megalocarpus and G. sepium; production during the fourth and fifth years after planting ranged between 2.8 and 4.9 t ha-¹ yr¹. Crop production in the agroforestry treatments was always lower than in sole crops due to below-ground competition for water and, in seasons with higher water availability, shading by the trees. Of the agroforestry systems examined, seed production for beans was highest under M. volkensii and G. sepium, followed by C. megalocarpus and S. spectabilis. Grain production in maize was greatest under C. megalocarpus, followed by G. sepium, S. spectabils and M. volkensii. Mean annual aboveground biomass production including maize grain and stover, bean seed, woody biomass and tree leaves in the M. volkensii treatment exceeded that for the sole crop plots, even though rainfall during 1996 and 1997 was only 61 and 95 % of the long term average. Although the biomass production of leaves was not estimated for S. spectabilis and G. sepium, the results obtained suggested that biomass production was greater than that obtained under sole crop cropping. The inverse correlation between tree and crop yield suggests that the value of the tree products must exceed the associated crop losses if benefits are to be obtained from agroforestry. M. volkensii is valued in areas of Kenya where markets for its products exist and therefore shows great promise for extension in semi-arid areas; where necessary, pruning may be used to reduce competition with crops and increase the length of clear bole. C. megalocarpus is widely used as a shade tree in East Africa and seems well suited for this purpose as its impact on adjacent crops was least of all the tree species examined. S. spectabilis, although having straight unbranched stems, exhibited a level of competition with adjacent crops that would necessitate a high value for its timber products to warrant its adoption. The least suitable tree species of those examined was G. sepium, whose poor form and susceptibility to attack by fungal pathogens and insects severely undermined its potential value for use in agroforestry systems.

The spatial variation of tree growth and site factors was studied in a silvopastoral system at Glensaugh in Northeast Scotland. Sycamore (Acer pseudoplatanus L). Hybrid larch (Larix x eruolepsis Henry) and Scots pine (Pinus sylvestris L) were planted at 5 m x 5 m, 7.1 m x 7.1 m and 10 m x 10 m spacings on plots replicated over three blocks in a Randomised Complete Block design on a rye grass (Lolium perenne L) pasture which was grazed by sheep yearly from April to October. Included in the design were an agricultural control, forestry control and mowed plots. The agricultural control had no trees but grazed pasture and the mowed plots had trees but the pasture was not grazed, instead it was cut at intervals and left to decompose on site. The forestry control plots had no pasture and as such were not given fertiliser treatments and soil samples were not collected from them, in these the trees were planted at the standard 2 m x 2 m spacings and fenced off from the animals. Pastures received 160 kg N/ha^-1 annum^-1 in four equal applications. The objective of this work is to study at tree-scale the spatial variation of tree growth and site factors in grazed and ungrazed silvopastoral system plots. Total soil N, available Mg and Ca, as well as organic matter (OM), %C, pH in water and Calcium chloride increased significantly with distance from the tree while P decreased significantly with distance from the tree in grazed plots. The presence of trees or animals alone in a treatment did not significantly influence soil nutrient redistribution in a silvopastoral system. Therefore it takes the combined presence of trees and animals in a silvopastoral treatment for a significant redistribution of soil nutrients around the tree to occur.

Coffee agroforestry systems (CAFS) sustain the livelihoods of many people globally at the same time as providing important ecosystem services such as carbon sequestration that help mitigate climate change. These systems vary in their composition (especially density and species of shade tree) and management. Changes made to enhance their productivity will affect their climate change mitigation potential. With growing food demand and diminishing availability of agricultural land due to global population growth, as well as an increasing threat from global climate change the trade-offs between the socio-economic and net carbon sequestration performance in CAFS are important. The carbon sequestration and socio-economic performance of a range of CAFS varying in composition and management were assessed in Costa Rica and Nicaragua. Measurements and modelled estimates were made of (i) greenhouse gas emissions (GHGs) from coffee cultivation (the carbon footprint (CF)), (ii) carbon sequestration potential into above-ground biomass and soil organic stocks and (iii) socio-economic performance (productivity and profitability), and their trade-offs analysed. The effects of agronomic management (conventional versus organic) and shade type (ranging from timber trees to full sun) on the CF of two long-standing CAFS experiments in Costa Rica Nicaragua demonstrated that management is the best predictor of the CF whereas shade type has a minor effect. The greatest contributor to the overall CF was N20 emissions from the input of J in applied organic and inorganic fertilisers. Shade systems with high levels of N input from leguminous tree pruning had the highest CF. Total soil organic carbon (SOC) decreased over the first nine years of coffee bush and shade tree establishment in these experiments, although this differed amongst soil layers. Organically managed systems tended to have an increase in SOC in the top 10 cm of soil, though organic and conventional systems had similar (larger) decreases in SOC in deeper soil. Shade type and above-ground biomass had a smaller effect on SOC. Comparison of the CF of these experimental CAFS treatments with their C sequestration potential showed that increases in GHG emissions from production intensification can be compensated for or even outweighed by the increase in C sequestration into above-ground biomass, especially for shaded systems. However, if less productive, lower intensity CAFS are extended onto an area of currently forested land in order to compensate for the shortfall in profitability (compared with higher-intensity, higher-yielding systems), this land-use change causes additional GHG emissions from deforestation. This results in net GHG emissions for the whole system for the majority of shade types tested. Evaluation of the C and socio-economic performance of coffee farms in the regions around the two experimental sites showed that due to the huge variation amongst CAFS there is no single strategy for climate change mitigation that could successfully be applied across the range of farms. Instead it will be necessary to carry out accurate and site-specific farm assessments to inform advice and decisions on system improvement tailored to the needs of individual farms and environmental settings. The findings of this research suggest that there is a place in the C market for CAFS, however their design and management will determine the overall net benefits that can be achieved.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior
The objective was to assess the changes promoted in the stocks and flows of C and N from the soil by farming systems agroforestry (agrosilvipasture - AGP and silvipasture - SILV) and traditional (TR), compared to natural vegetation of Caatinga (VN), after 13 years, the experiment was installed on a typical Ortic Chromic Luvisol, the city of Sobral, CearÃ. Soil samples were collected at depths 0-6, 6-12, 12-20, 20-40 and 40-60 cm, relief in four replicates per. Was determined by the total carbon carbon (TOC); total nitrogen (NT) and bulk density. The gas flow was measured using an analyzer in the field of O2, CO2, NO / NO x and SO 2 (UNIGAS Eurotron 3000). To this end, were used for still cameras based on galvanized steel and PVC cover installed in the field. The sampling was done in three replicates, considering the relief plan, convex and concave in each study situation. For each determination were performed triplicate, totaling nine chambers for relief. Soil samples were collected for determination of soil bulk density (Ds) and particle (Dp) and gravimetric moisture (Ug), which allowed the calculation of total porosity (Pt) and the pore space filled with water (EPPA). Among the agroforestry systems studied, the silvipasture, long-term, promoted greater reductions in C stocks and N, the system promoted agrossilvipastroil lower losses and represents a sustainable alternative to sequestration of soil C and N in the Brazilian semi-arid conditions. The traditional cropping system provided a reduction of 58.87 and 9.57 (Mg ha-1), which meant, a reduction of 6.5 and 1.06 (Mg ha-1), for those of TOC and TN, respectively. These results demonstrate the inadequacy of this system for the Brazilian semi-arid conditions. The concave topography (AGP) and flat (SILV) showed the highest values of TOC. For NT the concave shape (VN, AGP, and SILV) showed the highest values. Flows of C-CO2 varied with the time, AGP and SILV being similar to NV in the wet season, while in the dry season are higher. The TR has a different behavior, being higher during the wet season and similar to AGP and SILV in the dry. The flow behavior of NO present without a tendency similar to C-CO2: AGP and SILV presents similar to each other in the wet season, but smaller than VN. During the dry SILV and VN are larger than AGP. In TR NO was not detected in the two periods. The convex shape of relief TR system showed the highest values of C-CO2 fluxes in the wet season. In the dry season were found higher values of C-CO2 flows in AGP, SILV and RT, compared to NV flat terrain. Soil moisture was the variable most correlated with the fluxes of NO, what might be observed in systems SILV and AGP and VN convex reliefs.
Objetivou-se avaliar as alteraÃÃes promovidas nos estoques e fluxos de C e N do solo por sistemas agrÃcolas agroflorestais (Agrossilvipastoril â AGP e Silvipastoril â SILV) e tradicional (TR), comparativamente à vegetaÃÃo natural de Caatinga (VN), apÃs 13 anos, em experimento instalado sobre um Luvissolo CrÃmico Ãrtico tÃpico, no municÃpio de Sobral, CearÃ. Amostras de solo foram coletadas nas profundidades de 0-6, 6-12, 12-20, 20-40 e 40-60 cm, em quatro repetiÃÃes, considerando os relevos plano, convexo e cÃncavo em cada situaÃÃo de estudo. Nestas amostras foram determinados o carbono orgÃnico total do solo (COT), nitrogÃnio total (NT), densidades do solo (Ds) e de partÃcula (Dp) e a umidade gravimÃtrica (Ug), o que possibilitou o cÃlculo da porosidade total (Pt) e o espaÃo poroso preenchido por Ãgua (EPPA). O fluxo dos gases foi quantificado no campo utilizando um analisador de O2, CO2, NO/NOX e SO2 (UnigÃs Eurotron 3000). Para tanto, foram utilizadas cÃmaras estÃticas com base de aÃo galvanizado e tampa de PVC instaladas no campo em triplicatas, totalizando nove cÃmaras por relevo. Entre os sistemas agroflorestais estudados, o silvipastoril, em longo prazo, promoveu maiores reduÃÃes nos estoques de C e N, enquanto que agrossilvipastoril promoveu menores perdas, representando uma alternativa sustentÃvel para o sequestro de C e N do solo nas condiÃÃes semiÃridas brasileira. O sistema de cultivo tradicional (TR) apresentou reduÃÃo no perÃodo 13 anos de 58,87 e 9,57 Mg ha-1 (6,5 e 1,06 Mg ha-1 ano-1) dos estoques de COT e NT, respectivamente, o que comprova a nÃo adequaÃÃo deste sistema para as condiÃÃes semiÃridas brasileiras. Os relevos cÃncavo (AGP) e plano (SILV) apresentaram os maiores valores de estoques de COT, enquanto que para o NT, a forma cÃncava apresentou os maiores valores, no caso VN, AGP e SILV. Os fluxos de C-CO2 variaram com a Ãpoca, sendo AGP e SILV semelhantes à VN no perÃodo Ãmido, enquanto no perÃodo seco estes mesmos sistemas foram maiores. O TR apresenta comportamento diferenciado, sendo maior no perÃodo Ãmido e semelhante ao AGP e SILV no seco. Os fluxos de NO apresentaram comportamento com tendÃncia diferente do C-CO2: AGP e SILV apresentaram-se semelhantes entre si no perÃodo Ãmido, porÃm menores que VN. No perÃodo seco, SILV e VN foram maiores que AGP. No TR, o NO nÃo foi detectado nos dois perÃodos. O relevo convexo no TR apresentou os maiores valores de fluxos de C-CO2 no perÃodo Ãmido. No perÃodo seco foram encontrados maiores valores de fluxos de C-CO2 em AGP, SILV e TR em relaÃÃo à VN no relevo plano. A umidade do solo foi a variÃvel que mais se correlacionou com os fluxos de NO, o que pÃde ser observado nos sistemas SILV e AGP e na VN relevos convexos.

Communities in the Sahel region are confronted with problems such as depletion of soil fertility, food insecurity, and climate change, which exacerbate poverty and malnutrition for the inhabitants. The farmlands in Toukar, Senegal, are rapidly denuded of native trees, mainly Acacia albida, that provide myriad benefits. Agroforestry systems, or the intentional use of trees in croplands, have become a potential vehicle to transform the capacities of subsistence farmers to achieve food security. The purpose of this study is to determine farmers' attitudes about agroforestry, who seems to practice it and support it, who is unsure about its values, and who seems opposed to it. I find that farmers who practice a more intact historic version of the Serer farming system are the most supportive of agroforestry and tend to be wealthier, while people who are seemingly more modern are less likely to adopt it and tend to be poorer.

Face à la crise environnementale et climatique, les pratiques basées sur la gestion des processus écologiques ouvrent un nouvel horizon pour l’agriculture. L’enjeu actuel de l’agroforesterie basée sur les associations d’arbres, de cultures et d’élevage, n’est plus limité à la seule production, mais touche aussi à la durabilité́ de cette production, à la résilience du milieu cultivé vis-à-vis des aléas climatiques, à la fourniture des services écosystémiques et à la création de nouveaux « terroirs ». Il s’agit de concrétiser sa multifonctionnalité́ et son inscription dans le long terme. Or, ces pratiques agroécologiques ne peuvent pas résulter d’une pure application de recettes techniques ; elles se développent avec les caractères propres de chaque milieu accompagné par chaque agriculteur. L’entrée par les connaissances naturalistes et agroécologiques des agriculteurs, et par ce que l’on nomme paysage, peut-elle devenir un vecteur de transmission des pratiques agroforestières essentiellement par effet de voisinage et par apprentissage collectif ? Une étude critique des modalités et des dispositifs d’apprentissage, de transmission et d’accompagnement des pratiques agroforestières du Bassin francilien est menée à travers une démarche ethnopaysagère et géographique et par la sociologie pragmatique. Les récits des trajectoires agroforestières et en agriculture biologique ou de conservation des sols sont retracés à travers l’enquête ethnographique auprès d’agriculteurs et la collecte documentaire de terrain (photographies, dessins d’agriculteurs, plans de projets). Une typologie des différentes formes de paysages agroforestiers (linéaires d’arbres intra-parcellaire, complantés parfois d’une strate arbustive, maillage de haies champêtres, etc.) et la gamme des savoirs écologiques et de diversification qui y sont associés, est proposée. En regard, la méfiance envers les arbres chez certains agriculteurs de conservation des sols est identifiée. Dans un deuxième temps, l’enquête sur les modalités d’accompagnement par les parties prenantes du développement territorial (agriculteurs, propriétaires fonciers, agents des parcs naturels régionaux et des communautés de communes, vulgarisateurs), éclaire les conflits et les alliances entre acteurs territoriaux. Les outils et les processus d’apprentissage collectif de cette université agroforestière du dehors sont mis en évidence à travers les chroniques des ateliers de collectifs d’agriculteurs et des projets de recherche-participative autour du patrimoine de semences et de ligneux adaptés localement (enquête écologique, index-botanique, lecture et design paysager, ateliers de projets et de taille, sélection participative). Ce travail propose une synthèse des freins (le temps long, le manque de références locales et de savoir-faire de gestion, l’arbre dans le bail rural) et des conditions de transmission des pratiques agroforestières (implication des pionniers dans un groupe de pratiques, approche par l’expérience, implication des acteurs territoriaux). Celles-ci s’articulent entre différentes échelles : de la parcelle à la plaine, jusqu’à la communauté d’acteurs du « grand paysage ». Enfin, cette thèse identifie un ensemble d’expériences patrimoniales du vivant qui, à travers les bénéfices agro-écosystémiques et les filières alimentaires issus de ces nouveaux paysages agricoles, pourrait devenir le socle d’un projet local garant de la durabilité environnementale, sociale et économique du territoire
Faced with the environmental and climatic crisis, practices based on the management of ecological processes are opening up a new horizon for agriculture. The current challenge of agroforestry, based on associations of trees, crops and/or animals, is no longer limited to production alone, but also affects its sustainability and in particular the provision of ecosystem services and the food resilience of territories. However, these agroecological practices cannot result from the application of technical recipes. Can farmers’ naturalistic and agroecological knowledge of landscapes, become a vector for the transmission of agroforestry practices mainly through neighborhood effect and collective learning ? A critical study of the methods and mechanisms of learning, transmission and support of agroforestry practices in the Paris Basin is carried out through a transdisciplinary, ethno-geographic and pragmatic approach. The stories of their agroecological trajectories are retraced through ethnographic investigation and documentary collection from the field (photography, drawing of farmers, project plan). A typology of the different forms of agroforestry landscapes (intra-plot tree lines, diversified hedgerows gridding, etc.) and the range of ecological and diversification knowledge associated with them is proposed. In contrast, the mistrust of trees among some soil conservation farmers is identified. Secondly, the survey on the methods of support by stakeholders in territorial development (farmers, landowners, agricultural development associations, agents of regional nature parks and communities of municipalities), sheds light on conflicts and alliances between actors. The tools and collective learning processes of this outside agroecological university are highlighted through the chronicles of farmers' collective workshops and participatory research projects around the heritage of locally adapted seeds and woody plants (ecological survey, botanical index, reading and landscape design, project and pruning workshops, participatory selection). This work offers a synthesis of the brakes (the long time, the lack of local references and management know-how, the tree in the rural lease). And the conditions of transmission of agroforestry practices (pioneering attitudes, empirical and transversal approaches, involvement of territorial actors) are articulated between different scales: from the plot to the plain, to the community of actors in the large landscape. Finally, this thesis identifies a set of updating of living heritage which, through the agro-ecosystem benefits and the local food systems resulting from these new agricultural landscapes; could become the basis of a local project guaranteeing the environmental, social and economic sustainability of the territory

A 3 x 2 factorial experiment was conducted to examine the outcome and some of the competitive mechanisms between P. radiata (D. Don) and pasture for N and soil moisture. The factors examined were the monthly addition of 30 kg N/ha versus no additional N, and the manipulation of the level of pasture competition by spraying and simulated-grazing to give three levels of pasture competition. The experiment coincided with a period of severe drought which greatly increased the competition for soil moisture. Removal of pasture competition by spraying released a large amount of N into the soil mineral N pool. It also reduced overall demand for N and water because of the reduction in competition resulting in improved tree growth and greater N uptake by trees. However, it was apparent that moisture was the main limiting factor for tree growth in the plus-pasture treatments because, whilst trees did take up some of the applied N in the plus-pasture treatments, they showed no increase in growth and N uptake. A localized effect of trees on pasture dry matter production and N content occurred. Directly beneath trees and in the area predominantly occupied by tree roots competition for water and N was intense. Pasture response to N was greatest away from the tree rooting zone. Pasture appeared to compete successfully due to the nature of its root system which consists of a large biomass of very fine roots compared to the small biomass of fine pine roots in the surface soil. Competition between pasture and trees was further examined using the stable isotope 15N to trace a single 15N-labelled application of N fertilizer in spring. Recovery of 15N during the split fertilizer application program was assessed by periodic pasture harvests in the simulated-grazing treatment and by obtaining a complete balance sheet after 249 days. The dynamics of plant availability of applied 15N and retention of 15N in the soil was also followed. The recovery and retention of 15NO3- and 15NH4+ in particular were compared in the simulated-grazing treatment. Larger quantities of 15NO3- remained available to plants than 15NH4+ and 15N was still found in the KCl-extractable mineral N pool at 154 and 249 days after application. P. Radiate assimilated the same amount of 15N when added as 15NO3- or 15NH4+ in the simulated-grazing treatment but uptake into the aboveground biomass of pasture was greater for 15NO3- than for 15NH4+. However, pasture uptake of 15NO3- and 15NH4+ was not significantly different when pasture stubble and roots were include in the total recovery for all harvests. Removal of pasture competition increased the availability of 15N for the period just after application but 15N uptake by P. radiata was only doubled. There were no significant differences in 15N recovery between treatments in the 0-20 cm depth of soil; on average this was 49% of that applied. Total system recovery was 107, 92, 76, and 71% for the 15NO3-treated, 15NH4+ -treated simulated-grazing treatments, 15NH4+ -treated rank, and sprayed treatments, respectively. The loss of 15N from the system was not accounted for by leaching although this was not directly measured. In the sprayed treatment where the loss of 15N was greatest, it was thought that 15N loss may have been due to denitrification. The root systems of neighbouring trees did not overlap and midway between the trees there was apparently no competition between trees and pasture since no effect of tree roots on pasture growth and 15N uptake could be shown. Uptake by artificially-grazed pasture did not seem to reduce 15N movement into the canopy to the same extent as uptake by rank pasture. In the simulated-grazing treatment the increased cycling of N or reduced pasture root growth may have provided some benefit to tree uptake of 15N.

Trees in silvopastures may provide forage-livestock systems with multiple goods and services, including shade, shelter, and browse. Reports of forage and animal productivity from these systems indicate that, in some cases, animal gains are similar or better despite lower forage yield. The relationship between grazing system, body temperature, grazing behavior, and animal performance was explored in this study. Black walnut and honeylocust-based silvopasture systems were compared with open pastures in a randomized complete block design (r = 3) over three summers. Pastures were rotationally stocked with 5-7 lambs depending on forage availability. Lambs were weighed every four weeks. Behavior measures were recorded within a replicate within a week, and these measures were taken sequentially within three experimental periods. Ewe lambs (n = 3) were equipped with a vaginal temperature sensor (3 days) and an audio recording device (1 day) to detect prehension events. Cameras documented lamb behavior every 60 seconds. Forage measurements taken with a rising plate meter indicated greater productivity in the honeylocust silvopasture (5020 ± 30 kg · ha⁻¹ ) compared to the open pasture (4930 ± 30 kg · ha⁻¹ ; P = 0.0281), though forage availability in the black walnut silvopastures (3560 ± 30 kg · ha⁻¹ ) was lower than within the other treatments (P < 0.0001). There was no difference in animal gains between systems (P ≥ 0.4813), though gains were highest in the honeylocust silvopastures (25.6 ± 3.4 kg · period⁻¹ ), followed by the gains of the black walnut silvopastures (22.3 ± 3.4 kg · period⁻¹ ), and the gains of the open pastures (22.2 ± 3.4 kg · period- 1 ). Lambs in silvopastures spent more time lying down than animals in the open pastures (P ≤ 0.01), while lambs in the open spent more than two hours longer each day standing (P < 0.0001). During the hottest part of the day, ewes in the open pasture were 0.4 °C hotter than ewes in the black walnut silvopastures (P ≤ 0.0202). Lambs in the black walnut silvopastures grazed more (488 ± 14 minutes · day⁻¹ ) than lambs in the honeylocust silvopastures (438 ± 15 minutes · day⁻¹ ; P = 0.0192) and the open pastures (417 ± 14 minutes · day⁻¹ ; P = 0.0009), with no difference between the latter two systems (P = 0.3073). There was no difference in daily bites taken (P ≥ 0.7222), though lambs in the silvopastures grazed more frequently than lambs in the open pastures. In one six week winter grazing study, animal performance in the honeylocust silvopastures was compared with the productivity of lambs grazing the open pastures and the black walnut silvopastures. The objective of this study was to determine the effect of these pods on lamb growth when animals grazed stockpiled tall fescue (Schedonorus arundinaceus). Preand post-graze forage mass was estimated with a double sampling technique using a rising plate meter. Treatment pastures were rotationally stocked with three (walnut) or six lambs per experimental unit depending on forage availability. Fescue grab samples were collected every other rotation. Crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and total digestible nutrients (TDN) were estimated with a robust equation using NIR spectroscopy. Pre- and post-graze pod mass per hectare was estimated using randomly placed quadrats. Lambs were naïve to pods and did not readily consume the fodder until four weeks into the trial, and the methods for estimating pod intake were not sufficient to detect pod differences in pre- and post-graze pod mass. Forage availability in the honeylocust silvopastures (5130 ± 90 kg · ha⁻¹ ) and open pastures (5050 ± 90 kg · ha⁻¹ ; P=0.7580) was greater (P < 0.0001) than forage availability in the black walnut silvopastures (3790 ± 90 kg · ha⁻¹ ). Treatment had no effect (P = 0.3763) on average daily gains across the six weeks of the study. However, lambs within the honeylocust silvopastures had greater (P = 0.0251) average daily gains in the final period (0.12 ± 0.02 kg · day⁻¹ ) than lambs within the open pastures (0 ± 0.02 kg · day⁻¹ ), and lambs were observed consuming the pods. These data suggest that honeylocust pods may support greater gains of lambs, but that previous exposure and longer study periods in pasture settings may be necessary to see their nutritional benefit when grazing high quality forages.
Ph. D.