Tesi sul tema "Arid zone"

Chemical weathering reactions are important for the physical, chemical, and biological development of the critical zone. We present findings from aqueous phase chemical analyses of surface and soil pore waters during a 15 month study in a small semi-arid mountain catchment of the Santa Catalina Mountain Critical Zone Observatory. Stream water geochemical solutes are sourced to two distinct locations - fractured bedrock baseflow stores and soil quickflow stores. Solid phase observations of albite, anorthite, and K-feldspar transformation to Ca-montmorillonite and kaolinite are supported by stream water saturation states calculated via a PHREEQC geochemical model. While differences in mineral assemblages, soil depths, and horizonation suggest greater weathering in schist versus granite lithologies and in hillslope divergent versus convergent zones, soil pore water solute ratio analysis does not readily distinguish these differences. However, preliminary investigation of aqueous rare earth elements suggests detectable lithologic and landscape positional differences warranting focus for future research efforts.

Bibliography: leaves [148]-164.<br>This field study set out to identify the key ecological factors influencing the population dynamics of the Namaqua Sandgrouse Pterocles namaqua, through an investigation of diet and the nutritional demands during different stages of the annual cycle, the timing of breeding seasons and movements in relation to patterns of rainfall-dependent food availability, breeding success and the factors limiting productivity. In addition, the nesting habits and success of 11 coexisting arid-zone bird species were examined to test a variety of hypotheses regarding the relationship between nest-predation rate and nest site, nest density, predator-avoidance behaviour, stage of the nesting cycle and season, and degree of residency. Furthermore, the importance of rainfall as a breeding stimulus and its effects on clutch size were investigated for several species. The Namaqua Sandgrouse is an obligate granivore at all times, feeding on the seeds of annual plants, primarily of the family Fabaceae. Even while breeding, energy is the first-limiting nutrient in the foods of adults. Growing chicks have a proportionally greater protein demand, and are more dependent than adults on protein-rich legume seeds to satisfy first-limiting amino acid requirements. The chick growth phase was identified as the most nutritionally demanding stage in the annual cycle. The breeding season was found to be unexpectedly variable, and not consistently correlated with periods of peak food availability.

Magister Scientiae (Biodiversity and Conservation Biology)<br>Desertification deteriorates the landscape functionality of rangelands, affecting the resilience of biome boundaries which have a cascade effect not only in vegetation composition and characteristics but also in animal communities. The balance between plants and small mammals are essential in maintaining the functionality (i.e. nutrient cycling, soil stability, and water infiltration) of rangeland which includes the arid Steinkopf communal rangeland. However, the landscape functionality of rangelands has not been extensively studied, especially in communal areas where desertification is a serious concern since many people farm with livestock to survive. The aim of this study was to assess landscape functionality along an arid biome boundary and its relationship to small mammal assemblages. This study further aimed to provide a local landscape perspective of the current desertification process and projected expansion of the Desert Biome into more mesic biomes in South Africa. Three replicates for three Desert Biome, ecotone and Succulent Karoo Biome sites (27 sites in total) were selected to assess landscape functionality and survey small mammal assemblages over a one-year period. The change in landscape functionality between the three areas was assessed to determine the resilience of the biome boundary to desertification. For each small mammal survey, 216 live Sherman traps were set up during the summer and winter seasons to account for breeding, mortality, and possible migration. With the data, the body condition index, population density, and diversity were quantified.

Les zones arides abritent 35% de la population mondiale et affichent parmi les plus hauts niveaux de pauvreté. La faible quantité et l’hétérogénéité spatio-temporelle des précipitations et des écoulements compliquent non seulement l’exploitation de la ressource mais aussi la compréhension de ces hydro-systèmes. Cependant, depuis les origines de l’histoire humaine, les populations ont su domestiquer l’eau des zones arides, tant superficielle, que souterraine. Mais les dernières décennies ont vu certaines zones arides devenir le théâtre du développement d’activités industrielles aux usages d’eau intensifs qui posent des problèmes de gestion et d’accès à l’eau des usagers, en particulier des populations vulnérables. Dans le nord du Chili, le Désert d’Atacama est l’une des zones les plus arides au monde. Depuis les années 90, avec l'installation de grands projets miniers, la région a connu une croissance démographique et économique constante. L’eau souterraine y est intensivement utilisée pour les activités minières, l’approvisionnement des populations et l’agriculture. Afin de comprendre si les problèmes d’accès à l’eau souterraine de l’aquifère Pampa del Tamarugal, région de Tarapacá, sont dus au fait que la ressource est limitée, que la gestion des eaux souterraines doit être améliorée, ou encore à un manque d’information scientifique sur cette ressource, une approche multi et interdisciplinaire a été mise en place. Cette approche est constituée de deux grandes parties : d’une part, la caractérisation des ressources en eau souterraines de l’aquifère Pampa del Tamarugal. Pour cela, les données brutes existantes et leurs conditions de production ont été analysées et un nouveau réseau hydrométrique a été conçu grace à l’analyse multicritère couplée à une analyse SIG. Ensuite, la réalisation d’une carte piézométrique actualisée et la comparaison de cette carte avec les données piézométriques des dernières décennies ont permis de comprendre l’évolution de l’aquifère. L’étude géologique détaillée et l’analyse hydrochimique et isotopiques de sources et forages a permis de caractériser la recharge de l’aquifère, entre autres de définir le rôle prépondérant du substratum mésozoïque sur les écoulements notamment dans la couverture cénozoïque. Pour pallier au manque de données historiques, une approche complémentaire a été mise en place consistant en l’intégration des connaissances des populations locales indigènes pour l’élaboration du modèle hydrogéologique conceptuel. D’autre part, la gestion des ressources en eaux souterraines de l'aquifère Pampa del Tamarugal a été analysée, en s’attachant notamment à comprendre le rôle de l’information scientifique et technique et les stratégies et discours des acteurs sur cette gestion et sur les usages. Finalement, l’étude d’un système ancestral de gestion de l’eau a permis de générer l’information nécessaire à sa préservation en tant que patrimoine hydraulique de zone aride mais également à sa réutilisation pour la gestion actuelle de l’aquifère. Ces travaux de recherche ont permis d’améliorer la compréhension des mécanismes de recharge, ainsi que des écoulements et de l’évolution de la ressource en eaux souterraines sous pression anthropique dans une zone aride et montagneuse telle que le nord du Chili. Ils ont aussi permis de préciser les contraintes limitant l’accès à l’eau des populations vulnérables dans la zone d’étude, et le rôle de l’information scientifique dans la gestion de la ressource en eaux souterraines<br>Drylands are home to 35% of the world's population and have among the highest levels of poverty. The small quantity and spatio-temporal heterogeneity of rainfall and runoff complicate not only the exploitation of the resource but also the understanding of those hydro-systems. However, since the origins of human history, in arid areas, people have been able to domesticate both surface and ground water the water. But the last decades have seen some arid areas become the scene of the development of industrial activities with intensive water uses that pose problems of management and access to water for users, particularly vulnerable populations. In the north of Chile, the Atacama Desert is one of the most arid areas of the world. Since the 1990s, with the installation of major mining projects, the region has experienced constant demographic and economic growth. Groundwater is extensively used for mining, domestic supply and agriculture. In order to understand if the problems of access to the groundwater of the Pampa del Tamarugal aquifer, in the Tarapacá region, are due to a limited resource, management issues, or to a lack of scientific information, a multi-disciplinary and interdisciplinary approach has been put in place. This approach consists of two main parts: first, the characterization of the groundwater resources of the Pampa del Tamarugal aquifer. For this, the existing raw data and their production conditions have been analysed and a new hydrometric network has been designed with a multi-criteria analysis coupled with a GIS analysis. Then, the realization of an updated piezometric map and the comparison of this map with the piezometric data of the last decades allow to understand the evolution of the aquifer. Based on a detailed geological study and hydrochemical and isotopic analysis of sources and boreholes, the recharge of the aquifer has been characterized with the preponderant role of the Mesozoic substratum on the flows especially in the Cenozoic cover. To compensate for the lack of historical data, a complementary approach has been put in place consisting of integrating the local and indigenous knowledge for the development of the conceptual hydrogeological model. On the other hand, the management of the groundwater resources of the Pampa del Tamarugal aquifer was analyzed, with particular attention to understanding the role of scientific and technical information and the strategies and discourses of the actors on this management and on uses. Finally, the study of an ancient water management system has generated the information necessary for its preservation as a water heritage an arid zone but also in order to reuse this system for the current management of the aquifer. This research has improved the understanding of the Pampa del Tamarugal recharge mechanisms, as well as the flow and evolution of groundwater resources under anthropogenic pressure in an arid and mountainous area such as northern Chile. They also clarified the constraints limiting access to water for vulnerable populations in the study area, and the role of scientific information in the management of groundwater resources

This thesis is a comparative study of the life history strategies, and in particular seed germination requirements, in Australian species of the halophyte plant genus Frankenia L. (Frankeniaceae). Frankenia is a cosmopolitan genus that occurs in Mediterranean, semi-arid, and arid regions on distinctive soil types – commonly on saline, sodic or gypseous soils – in habitats such as coastal cliffs, and on the margins of salt lakes, salt-pans and saltmarshes (Summerhayes 1930; Barnsley 1982). The plants are small shrubs or cushion-bushes with pink, white or pale purple flowers, and salt-encrusted recurved leaves. This project investigates germination requirements for Frankenia in relation to seed age, light requirements, temperature preferences, salinity tolerance, and soil characteristics. It also explores two divergent reproductive strategies – notably seed packaging strategies – in relation to environmental variables. Within the 46 currently recognized endemic Australia species, some species have a few ovules per flower and produce only a few larger seeds per fruit, while other species have many ovules per flower and produce many small seeds per fruit. Large-seededness is thought to increase the probability of successful seedling establishment in drought and salt-stressed environments. As both larger- and smaller-seeded species of Frankenia co-occur in close geographical proximity, hypotheses regarding the advantages of large-seededness in stress environments can be tested. By restricting the analysis of seed mass variation to similar habitats and within a single plant genus, it is possible to test ecological correlates that would otherwise be masked by the strong effects of habitat differences and phylogenetic constraints. Overall, larger-seeded Frankenia species were demonstrated to be advantageous for rapid germination after transitory water availability, and for providing resources to seedlings if resources became limiting before their successful establishment. Smaller-seeded species delayed germination until both soil-water availability and cooler temperatures persisted over a longer time period, improving chances of successful establishment for the more slowly growing seedlings that are more reliant on their surroundings for resources. This study produces information on the seed and seedling biology of many Australian species of Frankenia including several that are of conservation significance, e.g. F. crispa with its isolated populations, and the rare and endangered F. plicata. This information is important for the development of conservation management plans for these and other arid zone, halophyte species. In addition, the results of this study are of practical significance in determining the suitability of Frankenia for inclusion in salinity remediation and mine-site rehabilitation projects, and for promoting Frankenia as a drought and salt tolerant garden plant.

The role of artificial watering points in the avifaunal dynamics of the semi-arid mallee woodlands of southeast Australia was examined. Species richness and abundance were monitored throughout the year at different distances from water to determine how birds were distributed around water points and how this changed in relation to environmental factors such as climate. Vegetation attributes were also measured to determine which factors explained patterns in the avifauna with distance from water, and also to allow a description of the vegetation in relation to the water points. Water points were monitored throughout the year to determine which species were utilising them, under which environmental circumstances and for what purposes. Knowledge of the water utilisation behaviour of individual bird species allowed some explanation of their distribution patterns, as well as an ability to predict the likely effects of water point closure on those bird species. The closure of two water points during the study allowed an assessment of the immediate effects of water point closure on avifauna (For complete abstract open document)

This thesis examines how our picture of the Epipalaeolithic of the southern Levant has been structured, what its evidential base is and how it has gained authority. Hitherto, research has focused on describing variability in microliths, the type-fossil of the period, in terms of archaeological cultures using typology. Narrative analysis was used in the first part of this thesis to explore the work of three main researchers in the field. This has shown that narrative strategies are indeed employed in archaeological texts to describe lithic and other data creating a picture of the period that relies substantially on ideas 'imported' from modern attitudes to the region and the relations of people within it. The techniques of narrative are used to pull together the disparate and conflicting data we work with into a unity of significance, embodying authority and plausibility. In the second part of the thesis, a study of 12 chipped stone assemblages from the Negev and southern Jordan was undertaken. Attribute analysis was used to explore variability within and between sites. This has revealed a complex and cross-cutting pattern of personal or local decisions taken within a context of wider norms, which has created very specific tool forms at individual sites. A picture of context dependent variability was discovered that has not been reflected in the traditional typological methods. This offers new ways of seeing the relationships between social organisations and material culture.

This thesis considers ways to improve biodiversity conservation at the bioregional level in Australia through the use of geospatial science technologies and biological modelling techniques. Following a review of approaches to biodiversity conservation at the bioregional level, including the roles and potential of geospatial science technologies in this regard, I consider biodiversity modelling using a case study of the Burt Plain bioregion in central Australia that focuses on selected taxa, ecosystems and landscapes. The Burt Plain bioregion was chosen since it is one of 19 bioregions nationally that has been given a 'very high' priority status for biological survey, assessment and potential reservation of land for conservation purposes. The specific research objectives for the Burt Plain bioregion study were to: · describe the species composition, distribution and nature of the dominant vegetation communities within the bioregion; · characterise environmental niche of communities with respect to selected environmental and management variables - latitude, longitude, climate, land systems and land units, geology, hydrography, topography, and tenure; · analyse how well or otherwise taxa have been sampled (during previous ground surveys) with respect to geographical and environmental variables; Biodiversity conservation at the bioregional level · develop and compare quantitative habitat models of the potential distribution of selected species based on presence-only distributional data; and · examine the significance of radiometric data as a potential correlate and predictor of the distribution of those selected species. National conservation initiatives such as the bioregional approach and international initiatives such as the biosphere reserves program to support the planning and management of biodiversity conservation are discussed in chapter two. The scientific and related processes underpinning the development of bioregions and strategies across the Australian states and territories are then considered. An important finding arising from this review is the need to improve biological information, especially through systematic surveys and on-going monitoring of ecosystems and populations of species, at the bioregional level to inform land use allocation and management. This finding is consistent with one of the general aims of the thesis to improve the spatial modelling techniques available for bioregional assessment and biodiversity conservation. In chapter three I review the role and limitations of geospatial technologies currently employed for biodiversity conservation management. Current developments and applications of GIS and remote sensing to wildlife research, conservation gap analysis and conservation reserve design are considered. Geographic information systems (GIS) are now routinely used by ecologists to Biodiversity conservation at the bioregional level analyse spatial data. Although various forms of GIS have been available for 15 to 25 years, the biological applications of GIS have figured most prominently in the ecological literature only in the past 15 years. The use of computer-generated models to simulate environmental events can provide a greater understanding of ecosystems, and offers improved predictive powers to conservation and land managers. The decision support offered by computer-based modelling techniques appears likely to underpin conservation and management decisions much more into the future providing that adequate biological and other datasets are available for this purpose. Dominant vegetation communities and various environmental gradients were analysed to characterise environmental niches at the bioregional scale for the Burt Plain bioregion (Chapter 4) and more locally at the catchment scale for the Upper Todd River Catchment (Chapter 5). In Chapters four and five I describe in detail the land tenure and use, land systems, climate soil, geology, topography, hydrology, vegetation and biodiversity of the Burt Plain bioregion and Upper Todd River Catchment. The bioregion contains some ephemeral watercourses, which are generally in fair to good condition, but are afforded little protection from a range of threatening processes, including grazing and trampling by feral animals and livestock and weed infestation. The major river systems occurring in the bioregion include parts of the Plenty, Hanson, Sandover and Lander Rivers. In the Upper Todd River Catchment the major watercourses Biodiversity conservation at the bioregional level are the Todd River and Station Creek, which exit the area via two narrow gaps in the low rocky hills on the southern boundary of the bioregion. The dominant geology can be summarised as plains and low rocky ranges of Pre-Cambrian granites on red earths. The bioregion has approximately 200 - 250 mm of summer rainfall, with rainfall occurring on 20 - 30 days per year. There is a high variability and range of temperatures, with an annual mean temperature of approximately 22-23°C. In Chapter six I consider a range of species found within the Burt Plain bioregion using existing survey data and techniques that enables the prediction of the spatial distribution of taxa. Using GLM and GAM models, Black-footed Rock- Wallaby (Petrogale lateralis), Spinifex Hopping Mouse (Notomys alexis) and Spencers Frog (Limnodynastes spenceri) were chosen for a more in-depth analysis. Environmental variables correlated with the presence of each species are then described and prediction maps showing the probability or likelihood of the presence of the species within the bioregion developed. In Chapter seven I examine the utility of radiometric data for wildlife habitat modelling. Statistical relationships are tested between the concentrations of the elements uranium, thorium and potassium and terrain characteristics such as position in the landscape, slope and aspect as well as other climatic variables. Radiometric data were found to be useful for developing statistical predictive Biodiversity conservation at the bioregional level models of six species: Red Kangaroo (Macropus rufus), Desert Dunnart (Sminthopsis youngsoni), Rabbit (Orcytolagus cuniculus), Brown Honeyeater (Lichmera indistincta), Little Spotted Snake (Suda punctata) and Southern Boobook (Ninox novaeseelandiae). I suggest that the utility of radiometric data for wildlife habitat modelling would appear significant and should be explored further using alternative quantitative modelling techniques and presence/ absence records for target faunal species. Predictions of species distributions may be useful for prioritising land acquisitions for reservation as well as in the future design of biological surveys. The thesis concludes with a synthesis of the major research findings, discussion of the limitations of the datasets available for the study, perspectives on management issues in the Burt Plain bioregion, and possible future research directions. It is important that purposefully-designed biological survey research be undertaken across the bioregions of the arid zone of Australia to enhance basic understanding of biodiversity patterns and their relationships to environmental heterogeneity and site-landscape level processes. Geospatial modelling techniques can assist such biodiversity survey and evaluation and make their conduct more cost-efficient and the inferences drawn from subsequent data analyses more powerful. This knowledge is required to contribute to the emergent concepts and theory of ecosystem dynamics and associated biodiversity patterns in arid Australia and, most significantly, to enhance the conservation and management of the unique biological complement and systems found in this region.

How individuals respond to environmental demands and pressures from conspecifics and from other species determines whether they will survive and reproduce, and hence whether their populations will persist. However, not all environments are benign or predictable, and not all populations of the same species respond to environmental pressures in the same way. The overall objective of this thesis was to incorporate both biotic and abiotic interactions into one conceptual framework to better understand and predict how species’ populations change across space and time. To help progress this objective, I built a trophic interaction model to capture the complexity of biotic and abiotic interactions in a model arid system, using long-term (over 20 years) ecological data on small vertebrates, climate and vegetation replicated across a large spatial area (8000 km2). The model was built upon smaller components that investigated the spatial and temporal dynamics of species’ populations and their biotic and abiotic drivers. A key achievement of this thesis is that it clarifies and confirms the importance of both biotic and abiotic interactions in arid resource-pulse environments. The trophic interaction model advances our knowledge on how interactions are context-specific and can change over space and time. It incorporates both bottom-up and top-down processes, and shows how the relative strength of these processes can change. I show also that simultaneous analysis of abiotic factors is important in predicting changes in species’ populations, and that biotic interactions (e.g. predation) can limit increases in consumer populations. In order to make accurate predictions about how species and ecological processes will respond to environmental change in arid systems, both biotic and abiotic factors need to be incorporated explicitly into models.

Research into seed biology and restoration ecology of areas disturbed by mining is crucial to their revegetation. Shark Bay Salt, a solar salt facility in the Shark Bay World Heritage Area in Western Australia has several areas of disturbance as a result of 'soil borrowing'. Soil from these areas termed 'borrow pits' was used to create infrastructure such as the roads and embankments surrounding the evaporation ponds. Many of the pits contain little to no vegetation after >10 years since disturbance ceased, hence research into their restoration is now essential. A vegetation survey at the site established the key species in the undisturbed vegetation, and investigated the vegetation in borrow pits subject to natural migration and topsoil replacement. The vegetation communities in the borrow pits were vastly different to those in the undisturbed vegetation, highlighting the need for research into revegetation. An investigation into the use of 'borrowed' topsoil on a small scale showed that seedling recruitment from 'borrowed' topsoil was generally similar in the donor site (natural vegetation) and the borrow pits. Due to the absence of topsoil for further revegetation, it was necessary to understand seed germination and dormancy characteristics to establish seed pre-treatments prior to seed broadcasting and seedling (greenstock) planting. An investigation into seed germination and dormancy characteristics of 18 common species revealed that most species germinated equally well at 26/13oC and 33/18oC, however seven species had improved performance at 26/13oC. Untreated seeds of seven species exhibited high germination. Seeds of two species had low imbibition, which increased with hot-water treatment, and hence require scarification for germination. Germination of seeds of three species substantially increased with gibberellic acid (GA3), smoke water (SW) and karrikinolide (KAR1, a butenolide isolated from smoke). Seeds of the remaining six species had low germination regardless of treatment. As a result, species were classified as likely to be non-dormant (44%), physiologically dormant (44%) or physically dormant (11%). Physiological dormancy of three species was at least partly alleviated by dry afterripening, whereby moisture content of seeds was adjusted to 13% or 50% equilibrium relative humidity and seeds were stored at 30oC or 45oC for several months. All iv after-ripening conditions increased germination percentage and rate of two species with one only germinating when treated with GA3 or KAR1. The germination of the third species was dependent on after-ripening temperature and seed moisture content.

The critical zone (CZ) is the heterogeneous, near-surface layer of the planet that regulates life-sustaining resources. Previous research has demonstrated that a quantification of the influxes of effective energy and mass transfer (EEMT) to the CZ can predict its structure and function. In this study, we quantify how climate variability in the last 3 decades (1984–2012) has affected water availability and the temporal trends in EEMT. This study takes place in the 1200 km² upper Jemez River basin in northern New Mexico. The analysis of climate, water availability, and EEMT was based on records from two high-elevation SNOTEL stations, PRISM data, catchment-scale discharge, and satellite-derived net primary productivity (MODIS). Results from this study indicated a decreasing trend in water availability, a reduction in forest productivity (4 g C m⁻² per 10 mm of reduction in precipitation), and decreasing EEMT (1.2–1.3 MJ m² decade⁻¹). Although we do not know the timescales of CZ change, these results suggest an upward migration of CZ/ecosystem structure on the order of 100 m decade⁻¹, and that decadal-scale differences in EEMT are similar to the differences between convergent/hydrologically subsidized and planar/divergent landscapes, which have been shown to be very different in vegetation and CZ structure.

La plaine du Souss est délimitée au nord par le Haut-Atlas, au sud par l’Anti-Atlas et à l’estpar le massif cristallin de Siroua. Les principales formations géologiques sont des marnocalcaireset conglomérats assez perméables, les calcaires du Turonien qui leur sont sousjacentset le lit fossile de l’oued Souss composé d’alluvions sablo-graveleuses trèsperméables.La nappe du Souss est la plus importante du sud du Maroc, elle est très exploitée par unsecteur agricole exportateur, la surexploitation de la nappe s’est traduite par une baissecontinue des niveaux. Depuis 1970, les prélèvements dépassent de loin les ressourcesrenouvelables de la nappe (déficit : 185 Mm3 en 1976, 358 Mm3 en 1998, 228 Mm3 en 2003).Le barrage d’Aoulouz est principalement destiné à la recharge artificielle de la nappe par deslâchers d’eaux stockées pendant les périodes pluvieuses. En zone semi-aride, une estimationprécise de la recharge est souvent délicate, la variabilité spatio-temporelle de la recharge étantgénéralement forte et les processus variés.Ce travail a permis de mieux caractériser l’impact de la recharge sur la nappe et d’évaluer letemps de séjour et le renouvellement des eaux souterraines.L’évolution de la piézométrie à la suite des lâchers d’eau à partir du barrage Aoulouz montredes remontées locales du niveau piézométrique sur la haute plaine, environ 85% des eauxlâchées à partir du barrage d’Aoulouz s’infiltrent 80 km entre Aoulouz et Taroudant.Toutefois, le niveau général de la nappe continue de baisser.Le faciès géochimique est principalement bicarbonaté calcique (dissolution des carbonates), etpar endroits sulfaté calcique (évaporites au pied du Haut-Atlas). Les eaux de surface ont unfaciès bicarbonaté calcique et magnésien acquis lors de leur circulation sur des calcaires et desdolomies.[...]<br>The Souss valley is bounded to the North by the High Atlas, to the South by the Anti-Atlasand to the East by the Siroua crystalline massif. The main geological formations arecalcareous marls of the Plio-Quaternary, the Turonian limestones that underlie them, and thefossil bed of River Souss formed by sands, sandstones and gravels from high permeabilityalluvium.The Souss aquifer is the most significant aquifer in southern Morocco, highly exploited by anagricultural exporting activity. Groundwater overexploitation induced a decreases ofpiezometric heads. Since 1970, water demand far exceeds renewable groundwater resources(balance defecit: 185 Mm3 in 1976, 358 Mm3 in 1998, and 228 Mm3 in 2003).The mean role of the Aoulouz dam is the artificial recharge of the Souss plain by release ofwater stored during rainy periods in the plain.In semi-arid areas, estimating recharge is often difficult, the spatial and temporal variabilitiesof recharge are generally high, and processes are varied.This work has enabled to characterize the impact of artificial recharge and to estimate therenewal of water in the aquifer.Water releases from Aoulouz dam has permitted an increase of the piezometric level on thehigh plain, about 85% of the water released are unfiltered in the first 80 Km between Aoulouzand Taroudant cities. However, the general water level decline goes on.The geochemical facies is mainly calcium bicarbonate type (dissolution of limestone), andlocally calcium sulphate type (evaporites of the High Atlas). Surface waters are a calcium andmagnesium bicarbonate types, acquired during their flow through limestones and dolomitesoutcrops.[...]

Riparian areas have been widely recognised by wildlife biologists as a critically important and functionally dominant component of terrestrial landscapes. This viewpoint has its genesis in high concentrations of species and individuals across a wide range of environments and strong interactions between riparian areas and the surrounding landscape. Despite major concerns regarding conservation management in the Australian arid zone, few studies have specifically examined the importance of riparian areas to the terrestrial bird fauna of arid and semi-arid Australia. This research aimed to examine the role of riparian areas in sustaining regional assemblages of terrestrial birds within the Australian arid zone. More specifically I asked: 1. How do riparian and upslope arid zone bird assemblages differ and to what extent are they interrelated? 2. Do these inter-relationships vary temporally with season, rainfall and year? 3. To what extent does surface water influence riparian and upslope bird assemblages? This study was carried out in semi-arid Mulga Lands bioregion of south west Queensland (c. 181000 km2) where bird densities, species richness and composition were compared among 124 sites which were distributed throughout the bioregion and surveyed over two seasons (summer, winter) and two years (1997, 1998). El Niño-related drought conditions prevailed over both seasons during 1997 but not 1998. Monthly rainfall was not dependent on either season or year. The extent to which the availability of surface water in these areas also influences terrestrial birds was investigated by comparing bird abundance, diversity and species composition at riparian and upslope sites, with and without permanent water. Upslope sites with permanent water were modelled using artesian bore drains. Overall bird densities were twice as high in riparian areas as upslope habitats but about 20% more species were found in upslope habitats. The estimation of species richness in circumstances where there are major differences in abundance emerged as an important issue for riparian-upslope comparisons. Riparian areas were also characterised by higher levels of species dominance and similarity in species composition than upslope areas. Riparian-preferring species accounted for 68% of total bird abundance and many were common in the surrounding landscape. Similarly, many upslope-preferring species were common in riparian areas. The number of species shared between riparian and upslope areas was maximised at riparian sites with permanent water, implying that these areas were of near-universal advantage. These results suggested that riparian habitats of the Mulga Lands exert a fundamental influence on the entire terrestrial avifauna and are therefore important centres of avian biodiversity. Despite high levels of climatic variation but only slight seasonal differences in mean rainfall and plant growth response, I observed a strong summer increase in species richness (overall and among many functional groups) but not in overall abundance. Fewer individuals and species were observed during the drought conditions of 1997. About half of the species (21 of 41) that could be individually categorised showed seasonal or inter-annual differences in occurrence, suggesting extensive inter-bioregional movements. Riparian usage was generally higher during periods of low monthly rainfall, but it was complicated by riparian interactions. Insectivores that forage mainly in the upper stratum, and seed-eaters such as pigeons, parrots and cockatoos, made greater use of riparian areas as rainfall declined, whereas the number of low-feeding insectivore species increased in riparian areas with increasing rainfall. Overall riparian usage was also higher during drought, but not necessarily summer. Species composition was strongly influenced by season, year and rainfall, and there were strong species composition linkages between riparian and upslope bird communities. These results support the proposition that riparian areas have an important if not crucial role in sustaining bird populations, not only during prolonged drought as refuge habitat, but also over much smaller time scales. Birds also responded strongly to the presence of surface water. The relative strength of the effects of riparian status and water availability were similar for most species and functional groups, although where differences were detected all favoured the effect of riparian status. Most species and functional groups showed specialised preferences for specific combinations of riparian status and water availability rather than generalised responses to either or both. Most displayed a dominant preference for riparian or upslope habitats and preferentially sought to meet their need for water within these areas. Because of the specialised responses, the presence of permanent water could only partially explain differences in bird assemblages between riparian and upslope sites. A significant role for higher productivity and/or structural complexity in riparian areas was suggested by strong associations between riparian status and vegetation structure that were only weakly related to the presence of surface water. Small insectivorous passerines, many of which are already uncommon or declining in other bioregions, appear most vulnerable to the planned closure of bore drains. This study suggests that, as far as the Mulga Land birds are concerned, the bird communities of riparian and upslope components of the landscape are functionally interrelated. This is despite strong structural and floristic differences in habitat, and the fact that many bird species show distinct preferences for one habitat or the other. Almost all terrestrial species were found in both the riparian and upslope habitats, although their use appeared to be strongly related to spatial and temporal variations in resource availability. As most birds are capable fliers, and changes in relative abundance were rapid, these patterns are likely to more strongly reflect movement between habitats (and in some cases, bioregions), than differences in recruitment and mortality. In fluctuating and unpredictable environments the ability to move between habitats may be an important adaptive strategy to dampen spatial and temporal variations in resources and facilitate species persistence. The overall picture is one of a shared and responsive avifauna. As many of the specific responses observed in this study appeared to be a predictable outcome of spatial variations in productive potential and temporal variations in resource availability, a conceptual model was proposed to explain spatio-temporal variations in terrestrial bird community organization in the Australian arid zone. The model establishes a graphical response domain, defined by a spatial axis that represents long-term cumulative outcomes of prevailing spatial and temporal productive processes (e.g. spatial variation in nutrient status, soil moisture and vegetation biomass) and a temporal axis that represents short-term availability of productive resources (e.g. rainfall). Within this domain, individual response surfaces were proposed to predict relative site-based differences in overall bird abundance, dominance, species richness, and inter-habitat movement. In addition to responses at average levels of resource availability, the response domain was also used to consider how birds might vary their use of the landscape under two extremes of environmental variability, drought and production pulses after extensive rainfall. The model may also predict assemblage differences in other biomes.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>School of Australian Environmental Studies<br>Full Text

L'olivier est un agrosystème pérenne clé pour l'économie du pourtour méditerranéen avec des pratiques culturales contrastées (sec épars/irrigué intensive, co-planté...). Connu pour ses mécanismes d'adaptations au stress hydrique et sa capacité de survivre durant de longues périodes à conditions limitantes en eau de sol, l'oléiculture pluviale est dominante dans cette zone, notamment en Tunisie et l'écartement entre les arbres est une fonction de la distribution de la pluviométrie (un nombre important de pieds à l'hectare au Nord (6 m) et des oliveraies très éparses au Sud (25 m)) assurant un volume de sol exploré par les racines supposé être suffisant pour satisfaire les besoins en eau des oliviers. Il est cependant soumis à une forte pression climatique du fait des sécheresses récurrentes dont la fréquence et l'intensité risquent de s'accentuer dans les décennies qui viennent. La réponse de ces couverts épars, où l'eau est un facteur limitant, à ces changements climatiques est méconnue. Dans ce contexte, ce travail vise à améliorer notre connaissance des processus physiques régissant le cycle hydrologique et le développement de la végétation dans une oliveraie pluviale au centre de la Tunisie. L'objectif de cette thèse est double : i/tester la vulnérabilité de ces oliveraies éparses face aux conditions extrêmes futures et ii/proposer des solutions aux agriculteurs à court (par exemple l'irrigation localisée de complément) et à long termes (notamment la diminution des écartements entre les arbres ou l'extension des périmètres irrigués). Pour répondre à ces objectifs, nous avons besoin de bien caractériser le fonctionnement thermo-hydrique des oliviers, d'identifier la possibilité de suivre leur état hydrique actuel et de prédire leurs réponses à des conditions hydriques futures plus sévères. Dans un premier temps, un protocole expérimental dédié qui comprend des mesures par la méthode de fluctuations turbulentes et la méthode de flux de sève a été mis en place. Les données collectées qui renseignent sur les échanges d'énergie et de matière au sein du continuum sol-plante-atmosphère, ont été analysées et leur cohérence a été vérifiée à travers une étude des différentes composantes des bilans hydrique et énergétique à différentes échelles spatiales et temporelles. En plus de mesures directes, des mesures de proxidétection ont été sélectionnées afin d'analyser l'apport de cet outil puissant. Des relations entre les indices de stress hydrique estimés (par exemple l'écart entre la transpiration réelle et potentielle) et les indicateurs de proxidétection (la température de surface et le photochemical reflectance index) ont été donc établies pour détecter les seuils critiques au-delà des quels un apport en eau devient indispensable pour la survie de la plante. Dans un second temps, un modèle d'échanges sol-plante-atmosphère ISBA a été calé et validé en s'appuyant sur l'important jeu de données observé pour reproduire le fonctionnement des oliviers. Cette étude souligne que le caractère épars des oliviers est néanmoins un défi pour l'application de ces outils car la fraction de couverture de végétation (moins de 7 % pour notre site de Nasrallah) est telle que la surface est dominée par le fonctionnement du sol nu. Des ajustements ont été donc proposés voire apportés aux méthodes utilisées pour les adapter à ce faible taux de couvert végétal. La base de données utilisée pour cette étude est publiée sous le DOI : 10.6096/MISTRALS-SICMED.1479<br>The olive tree is a key perennial agrosystem for the economy of the Mediterranean basin with contrasting farming practices (rainfed sparse/intensive irrigated, co-planted ...). Known for its mechanisms of adaptation to water stress and its ability to survive for long periods under soil water limiting conditions, rainfed olive cultivation is dominant in this area, especially in Tunisia and the spacing between trees is a function of the distribution of the precipitation (from high density of plantation in the North (6 m) to very sparse in the South (25 m)) ensuring a volume of soil explored by the roots that is assumed to be enough to satisfy the water needs of the olive trees. However, it is subject to severe climatic pressure due to widespread dry spells, for which the frequency and intensity is likely to increase in the coming decades. The response of these sparse covers, where water is a limiting factor, to these climatic changes is unrecognized. In this context, this work aims to improve the current understanding of the physical processes governing the hydrological cycle and the development of vegetation in rainfed groves in central Tunisia. There is a twofold purpose: I / to test the vulnerability of these sparse olive groves to future conditions and ii / to make a decision support to farmers for the short (i.e., localized supplementary irrigation) and in the long term (in particular a decrease of the spacing between trees or the extension of irrigated area). To meet these goals, it is necessary to characterize the thermo-hydric functioning of olive trees, to identify the possibility of monitoring their current water status and to predict their responses to more severe future water conditions. As a first step, a dedicated experimental set up that includes eddy covariance and sap flow measurements has been installed. The collected data, which provide information on the exchange of energy and matter within the soil-plant-atmosphere continuum, were analyzed and their consistency was verified through a study of the different components of the water and energy balances at different spatial and time scales. In addition to direct measurements, proxidetection measurements are available and allow investigating the benefit of this powerful tool. Relationships between the estimated water stress indices (e.g., the difference between actual and potential transpiration) and the proxidetection indicators (surface temperature and photochemical reflectance index) were therefore established to detect critical thresholds beyond which a water supply becomes essential for the survival of the plant. In a second step, a soil-plant-atmosphere ISBA exchange model was calibrated and validated based on the large data set observed to reproduce the functioning of olive trees. This study emphasizes that the sparse nature of olive trees is nevertheless a challenge for the application of these tools because the fraction of vegetation cover (less than 7% for our Nasrallah site) is such that the surface is dominated by the bare soil functioning. Adjustments have therefore been proposed or even applied to these methods to adapt them to this low fraction vegetation cover. The database used in this study is published under the DOI: 10.6096/MISTRALS-SICMED.1479

La question de l’accès à l’eau potable se pose avec acuité pour les pays de la régionsubsaharienne où un individu sur trois n’a pas accès à une source d’eau améliorée.L’objectif de cette thèse vise à définir les conditions d’une gestion durable de l'eau pourla ville de Djibouti. Dans ce contexte, la question de l'approvisionnement en eau estenvisagée dans une perspective patrimoniale afin de tenir compte des particularités dela ressource en zone aride et des usages spécifiques qui lui sont associés dans unenvironnement marqué par la pauvreté. Un apport majeur de la thèse réside d'une partdans l’analyse du contenu d’une politique durable de l'eau à Djibouti en présenced’inadéquation entre l’offre et la demande de l’eau et, d'autre part, des implications decette politique en termes de tarification de la ressource selon les usages mais aussi enterme de répartition plus équitable de l'eau au sein de la population. La première partiede la thèse s’intéresse à l’étude de la disponibilité de cette ressource rare à travers sonmode de gestion ainsi qu’à sa mesure à l’aide d’indicateurs. Elle propose également uncadre d’analyse de la ressource en resituant les principaux concepts utiles à ladéfinition d’une gestion durable de l’eau. La seconde partie met l’accent sur l’analysedes déterminants de la demande en eau et des choix en matière d’approvisionnementpour Djibouti-ville. Pour ce faire, elle s’appuie sur une étude économétrique réalisée àpartir d’enquêtes auprès d’un échantillon de 400 ménages. L’estimation d’un modèleprobit multivarié permet de considérer que le choix d’être raccordé à un branchement àdomicile dépend des caractéristiques socio-économiques du ménage. Cette thèseapporte des résultats originaux sur l’accès à l’eau des ménages et montre en particulierle rôle joué par des facteurs tels que le revenu, la taille de la famille ou le niveaud’éducation du chef de famille dans les choix opérés par les ménages<br>The issue of access to drinking water is one which is of paramount importance for thecountries of the sub-Saharan region where one individual out of three does not haveaccess to a water source. The aim of this thesis is to determine the conditions ofsustainable water management for the city of Djibouti. In this context, the issue ofwater supply is considered from an asset perspective in order to take into considerationthe peculiarities of this resource in a dry zone and its uses in particular in anenvironment marked by poverty. The main contribution of this thesis lies not only inthe analysis of the content of a sustainable water policy in Djibouti at a time when isthere is discrepancy between supply and demand, but also with an examination of theimplications of such a policy in terms of the pricing of this resource based on both itslevel of use and on a more even distribution within the population. The first part of thisthesis deals with an analysis of the access to this scarce resource according to how it ismanaged and measured with the help of indicators. A framework is then developedwith the help of some main concepts that are useful for defining a sustainablemanagement of water. The second part emphasizes the study of the determinants ofdemands in water and the choices in terms of the supply for Djibouti-city by using aneconometric study based on investigations into a sample of 400 households. Theassessment of multivariate probit model allows taking into account the connection of ahousehold to the service depends on its socio-economic markers. This thesis generatenew findings about household access to water supply and highlights the extent towhich such factor as income, the household size or the level of education of the head ofthe family influence the choices made by the household

The phylogenetics and biogeography of the following four groups of unrelated terrestrial non-passerine birds, that have endemics in both the south-west and north-east arid-zone lowlands (and Sahel), and which also encompass taxa with differing habitat tolerances, mobility and life-history traits, were examined: the bustards (Otididae), sandgrouse (Pteroclidae), coursers (Glareolidae) and Stone Partridge (Ptilopachus). Another aim of this research is to use insights from the evolutionary relationships of these families to assess the current state of their taxonomy, as well as to assess character evolution and other life history attributes (including evolution of their mating systems).

Since pastoralism began in Australia???s rangelands, the number of artificial watering points (AWPs) has increased dramatically, such that today, few areas of rangeland are further than 10 km from water. This increased availability of water has caused many ecological impacts. Unfortunately, such impacts are poorly understood in the context of an Australian conservation reserve, thus hindering strategic management. This study examined the spatial distribution of vertebrate (kangaroos, small mammals, lizards and avifauna) and vegetative variables around open AWPs as well as AWPs that have been closed since pastoralism (sheep-grazing) ceased nearly thirty years ago in Sturt National Park, arid New South Wales. The study also examined vertebrate use of AWPs, with a particular emphasis on kangaroos and avifauna. The study revealed that most variables showed few differences in spatial distribution with distance from open and closed AWPs, thus suggesting that the observed piospheric impacts were primarily attributable to historical sheep-grazing. Indeed, piospheric patterns were weak suggesting some recovery over the last thirty years. That kangaroos did not exhibit water-focused grazing is no surprise, since despite their regular use of AWPs, particularly during hot, dry times, the current spatial arrangement of AWPs facilitates regular travel to, and from, such resources allowing kangaroos, like much other fauna, to distribute themselves in relation to food and shelter preferences rather than in relation to water supply. In contrast, the majority of avifaunal groups (excluding ground-dwelling species) were clustered around open AWPs, often irrespective of season, because of food and water requirements. Such spatial concentrations of avifauna are thought to cause a range of interspecific effects. Experimental AWP closure and GIS modelling showed that whilst closure of AWPs will increase the average distance to water, which will have key benefits, the majority of areas in Sturt National Park would still be accessible to most water-dependent species even if all unused AWPs were closed. Strategic retention of AWPs to replace water sources lost since European settlement, aid threatened and migratory species??? conservation and enhance nature-based tourism opportunities is thus recommended and an example of a strategic management and monitoring plan outlined.

La liaison entre la teledetection des etats de surface et l'hydrologie est etudiee sur deux sites, revelant l'importance des problemes d'echelle et la necessite d'informations hydrologiques de type versant. Sur les bassins du real collobrier (var, france) apres des corrections imposees par le fort relief, le traitement de l'imagerie satellitaire conduit a une cartographie des essences forestieres. La part d'ecoulement relative a chaque zone homogene est calculee a des pas de temps annuel, trimestriel, mensuel et sur des episodes. Une liaison coherente entre zones et types d'ecoulement est obtenue mais la signification exacte de zone homogene, et le manque d'observations hydrologiques de versant rendent la validation delicate. Sur des bassins saheliens, un traitement d'image specifique a des zones heterogenes est mis au point, base sur une detection en deux niveaux: paysage, puis etats de surface type du sahel. Le ruissellement elementaire correspondant est agrege sur le bassin versant selon le modele lineaire de l'orstom. Certaines zones non contributives en grand rendent indispensable une approche complementaire a un autre niveau d'echelle

Buffel grass (Cenchrus ciliaris ) has been established in Uluṟu‐Kata Tjuta National Park since 1968. To date, the influence of buffel grass on the Park's flora and fauna has been largely unassessed. The objectives of this study were to determine if buffel grass dominates vegetation communities at the base of Uluṟu and if buffel grass habitats are associated with lower reptile and amphibian species richness than endemic vegetation communities. We used vegetation transects to measure the amount of buffel grass and genera of endemic vegetation at 26 sampling locations around the base of Uluṟu. The vegetation survey data were paired with pitfall trap data from reptile and amphibian captures at the same sampling locations. Indicator species analysis and non‐metric multidimensional scaling were used to analyse the vegetation and herpetofaunal community data. Our analyses determined five distinct vegetation communities around Uluṟu. At the base of Uluṟu, buffel grass dominated half of sampled areas and the rest of the inselberg's base was dominated by Themeda grasses. Buffel grass habitats had significantly higher herpetofaunal species richness than the Themeda habitats that dominated other areas at Uluṟu's base. Herpetofauna species richness in buffel grass‐dominated habitats was also significantly higher than all vegetation communities except for Triodia‐dominated habitats. These observations do not directly indicate that buffel grass presence promotes higher species richness of reptiles and amphibians since the observed patterns may be driven by factors such as proximity to breeding sites and abiotic variables not directly related to the grass itself.

This thesis presents an independent, sediment-based record of landscape change within an agricultural hinterland. Established historical and archaeological sequences document the primary occupation of Anuradhapura, Sri Lanka’s ancient capital, beginning ca. 400 BC and lasting until it was largely abandoned in AD 1017. Anuradhapura is located in the island’s dry zone, which depends almost completely on the unpredictable Northeastern Monsoon for water. Oral history and historical narratives have long held that large-scale irrigated rice cultivation took place in the hinterland to produce an agricultural surplus that sustained the urban and monastic populations. However, until the onset of the Anuradhapura Hinterland Project in 2005, the archaeological record of the hinterland was undocumented, leaving existing narratives untested. The geoarchaeological research presented here was undertaken as part of the Hinterland Project, in order to document the chronology and cultural and environmental processes that contributed to the formation of this irrigated landscape. Optical dating of sediments demonstrates that the onset of large-scale irrigation began ca. 400 BC, and the construction of new works continued until Anuradhapura’s late occupation period. Sampled reservoirs and channels began to infill, indicating widespread disuse, within ca. 100 years of Anuradhapura’s abandonment. Soil micromorphology and bulk sediment characterisation document hinterland habitation, water management, and cultivation activities prior to the establishment of large-scale irrigation. This work illustrates the coping strategies that people employed to deal with the vagaries of the dry zone environment and demonstrates that hinterland land use changed throughout the primary occupation period. Although largescale irrigation works infilled relatively rapidly, cultural activity and land use re-emerged following this period of disuse.

Rainfed areas in the Dry-Zone of Sri Lanka are characteristic of extensive marginal agro-ecosystems known as the semi-arid tropics (SAT) populated by poor farming communities. In the Dry-Zone and elsewhere, the traditional response to seasonal water scarcity was to construct rainfall-harvesting devices known as ‘tanks’; created by building earthen dykes across ephemeral streams in undulating terrain. Most are held in common ownership by adjacent communities, who use them for multiple functions including irrigation, bathing and fishing. Storage efficiency is enhanced by arranging tanks in cascading sequence within watersheds so that drainage waters can be re-used. The aim of this study was to evolve improved collective strategies for the management of seasonal water bodies (focussing on aquatic production) in order to reduce the vulnerability of the poorest groups. Understanding of these complex systems requires a holistic approach which integrates hydrological, biological and socio-economic factors on a suitable (watershed) scale. Work commenced with a comprehensive situation analysis, culminating with the formulation of a participatory research agenda for action research based on low-input stocking enhancements. Village livelihoods have traditionally revolved around paddy cultivation as the primary tank function; however, in recent times, water-use strategies have responded to a range of demographic, economic and environmental pressures with implications for the sustainable management of natural resources, especially living aquatic organisms. Natural fish production in the most seasonal tanks relies on intermittent spill-events which link successive tanks; these provide migration routes which permit recruitment of stocks from lower perennial tanks. Rehabilitation initiatives that increase the storage / irrigation capacity of tanks or poorly designed surplus weirs that impede migration have negative impacts on fisheries, though they are rarely considered by planners. The fundamental concept of the purana complex (PC) as the smallest logical sub-component of the watershed for intervention is introduced. Within PC boundaries discrete community groups bound by ties of kinship and caste, control access to private and commonly held natural resources. PCs in the uppermost reaches of watersheds are distinguishable by the highly seasonal nature of their tanks and poor physical infrastructure relative to lower watershed communities. Such areas are also often buffer zones between as yet uninhabited hinterlands and settled areas where cultivation potentials are further restricted due to wild animal incursions. Consequently, these groups exhibit the greatest dependence on exploitation of the natural resource base. This often includes less seasonal tanks in lower PCs where fisheries are of less significance to local livelihoods. Such low-level ‘poaching’ is generally well tolerated, but potential for conflict exists where development efforts restrict hitherto free access to these resources. These findings were the basis for two phases of action research which involved the stocking of ten tanks belonging to seven communities in North West Province (2000-2001). Phase 1 trials encompassed a range of social and physical and settings from lower to upper watershed. Results indicated that the use of costly hatchery-produced seed was unlikely to be sustainable given (1) a background of highly erratic natural production (2) uncertain returns to individual effort and (3) a low priority accorded to fish production from village tanks given the availability of low-cost commercial production from perennial reservoirs. The second phase was restricted to low-caste communities in upper watershed areas and relied entirely on wild-fish stocks captured from perennial reservoirs lower in the watershed. Also emphasis was on intermittent ‘staggered’ harvesting using hook and line gears rather than the single intensive ‘collective harvests’ adopted in phase 1 trials. High yield potentials were demonstrated in the smallest tanks (<4ha) which were devoid of fish stocks during two pervious drought years. Results also indicate that sustainable adoption will be likely only where there is strong social cohesion and representative village leadership. An adaptive learning process which can demonstrate the net benefits of staggered harvesting in seasonal tanks is described. These stocking strategies combined with tank rehabilitation sympathetic to preservation of upstream hydrological linkages, are highly complementary enhancement steps. Results clearly show that together they have potential to maintain the wider aquatic ecosystem on which the poorest groups depend.

Over the period 1961 – 90 the North East Arid Zone of Nigeria experienced a decline in annual rainfall totals and increased aridity which placed increasing pressure on rain fed, millet-based farming systems. The changes in seasonal rainfall total and distribution have been examined and it has been shown that the rate of decline has been consistent across the region. The decline has been dominated by reduction in the number of rain days during the middle of the rainy season and there is no evidence of a significant change in the length of the growing season. Over the same time period, there has been a small, but significant, increase in mean air temperature which has resulted in a small increase in potential evapotranspiration. Other climatic parameters (vapour pressure, solar radiation and wind speed) appear to have remained stable, although the paucity and dubious quality of much of the historical meteorological data make rigorous statistical analysis difficult. A water balance model (BALANCE) developed by the author, was calibrated for a millet crop grown on a typical sandy loam soil in Maiduguri (Nigeria). The model was necessarily parsimonious, but was shown to perform well when calibrated against observed soil water content. However, the empirical nature and high sensitivity of key parameters relating to bare soil evaporation and drainage mean that it is difficult to parameterise the model by laboratory, or independent field measurements. Applying the calibrated model to daily rainfall and average evapotranspiration data from Nguru (Nigeria) for the period 1961 – 93 showed that, with the exception of extreme drought years, the increased aridity would have had little impact on the viability of traditional millet and millet-cowpea intercropping systems prior to the early 1980s. However, after that date, predicted seasonal millet transpiration, and hence predicted yields, have declined, and long duration cowpea intercrops, which were traditionally matured on residual soil moisture after the millet harvest have had insufficient water. Whilst the BALANCE model has been useful in examining the impact of climatic variability on agro-hydrology, it is not a crop physiological model and the interaction between soil water and crop development is poorly represented. The model cannot, therefore be applied with confidence to investigate the potential yield benefits of physical or agronomic interventions to alleviate the impacts of aridity. Although more complex models exist to do this, they require detailed parameterisation of the crop physiology, which was not possible within the scope of this study.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico<br>A Ãgua na bacia hidrogrÃfica està distribuÃda em diversos compartimentos importantes no que se refere à ecohidrologia. Muitos estudos em regiÃes semiÃridas apontam os reservatÃrios superficiais como principais compartimentos de Ãgua. Entretanto, a bacia hidrogrÃfica tem maior abrangÃncia que as bacias hidrÃulicas nela contida, e os recursos hÃdricos nos compartimentos distribuÃdos na bacia hidrogrÃfica (como no solo) devem ser analisados nÃo somente no que se refere aos usos ecolÃgicos, mas tambÃm como espaÃo de disponibilidade hÃdrica. Portanto, o objetivo do trabalho foi analisar, com base em medidas e modelagem, a dinÃmica da Ãgua nos solos de uma bacia semiÃrida de Caatinga preservada e seu impacto sobre a disponibilidade hÃdrica. Para isso foi medida, entre outros, a umidade do solo a cada hora, de 2003 a 2010 (2923 dias) na Bacia Experimental de Aiuaba (BEA, 12 kmÂ), totalmente preservada e com precipitaÃÃo mÃdia anual de 560 mm. O monitoramento foi realizado atravÃs de trÃs sensores TDR, um instalado em cada uma das trÃs associaÃÃes entre solo e vegetaÃÃo (SVA) identificadas na bacia. O mÃtodo de investigaÃÃo considerou seis etapas principais: i) determinaÃÃo da profundidade efetiva das raÃzes da Caatinga preservada; ii) calibraÃÃo dos sensores de umidade tipo TDR; iii) representaÃÃo espaÃo-temporal da umidade do solo em cada unidade de SVA; iv) anÃlise da disponibilidade hÃdrica do solo na zona das raÃzes; v) parametrizaÃÃo do modelo hidrolÃgico WASA-SED; e vi) parametrizaÃÃo do modelo hidrolÃgico DiCaSM. Os resultados obtidos nesta pesquisa indicam a importÃncia da abordagem da anÃlise temporal da umidade do solo e da disponibilidade hÃdrica do solo na zona das raÃzes para a manutenÃÃo do bioma Caatinga. Mais especificamente, foi observado que a profundidade efetiva do sistema radicular na BEA oscilou entre 70 e 80 cm nas regiÃes com solos profundos, porÃm, em regiÃes com solos rasos, observou-se que a profundidade efetiva das raÃzes adaptou-se Ãs restriÃÃes, ficando reduzida a menos de 40 cm. AlÃm disso, a anÃlise sazonal demonstrou que, na estaÃÃo de estio, as raÃzes tÃm comprimentos atà 11 cm menores, abrindo, portanto, poros secundÃrios que facilitarÃo a penetraÃÃo da Ãgua nas eventuais chuvas dos meses secos (junho a dezembro), assim como nas primeiras chuvas da estaÃÃo Ãmida. Nas duas SVAs cujos solos sÃo profundos e cuja vegetaÃÃo à densa, a Ãgua no solo encontra-se ânÃo-disponÃvelâ (isto Ã, abaixo do ponto de murcha permanente â WP) em quase nove meses ao ano (72% do tempo); e somente durante trÃs meses ao ano (25%) a Ãgua no solo encontra-se disponÃvel. Nos 3% restantes do ano (cerca de 10 dias) hà Ãgua gravitacional nessas SVAs. Na SVA cujo solo à raso e cuja vegetaÃÃo à esparsa, a dinÃmica da Ãgua no solo à diferente: o tempo em que hà Ãgua gravitacional, disponÃvel e nÃo disponÃvel à praticamente o mesmo (quatro meses ao ano). Isso se deve, entre outros, à baixa umidade do solo no ponto de murcha permanente do neossolo litÃlico; e à sua restrita espessura, gerando saturaÃÃo muito mais frequentemente que nos demais solos que â ao contrÃrio deste â dispÃem de drenagem profunda. A depleÃÃo da Ãgua no solo sob condiÃÃes de umidade abaixo do ponto de murcha foi outro resultado importante desta pesquisa. Nas duas associaÃÃes com solos profundos e vegetaÃÃo densa, observou-se â ao longo de todo o perÃodo investigado â decaimento contÃnuo da umidade atà que a mesma se aproximasse assintoticamente da umidade residual. AnÃlise mais detalhada demonstrou que a reduÃÃo da umidade do solo entre o WP e a umidade residual sempre obedecia ao decaimento exponencial. Na associaÃÃo com solo raso e vegetaÃÃo esparsa observou-se que a umidade nÃo caÃa para valores inferiores ao WP, mesmo sujeita ao mesmo rigor climÃtico das demais associaÃÃes. Considerando-se: (i) que em solo tÃo seco, a drenagem à improvÃvel; e (ii) que os processos associados de percolaÃÃo e evaporaÃÃo tampouco devam ser os responsÃveis pela retirada de Ãgua do solo (posto que o fenÃmeno nÃo se observa na SVA cujo solo à raso e, portanto, mais quente); levanta-se a hipÃtese que o secamento do solo nessas condiÃÃes deva ser causado por extraÃÃo de Ãgua pela vegetaÃÃo. Isso reforÃaria a tese de que a Caatinga dispÃe de adaptaÃÃo para sobreviver mesmo em condiÃÃes de estresse hÃdrico. Os modelos hidrolÃgicos WASA-SED e DiCaSM nÃo conseguiram representar adequadamente a dinÃmica temporal da Ãgua nos solos da BEA. No entanto, os modelos reproduziram satisfatoriamente as curvas de permanÃncia da umidade dos solos, permitindo representar a disponibilidade hÃdrica na zona das raÃzes para fins de planejamento. Por fim, logrou-se avaliar â quantitativa, espacial e temporalmente â a disponibilidade hÃdrica do solo. Esta à da mesma ordem de grandeza da disponibilidade de um reservatÃrio superficial Ãtimo. Em termos quantitativos, a disponibilidade no solo chega a ser quase cinco vezes superior à do reservatÃrio superficial, entretanto, a garantia associada da Ãgua superficial (90%) à bem superior à permanÃncia da Ãgua disponÃvel na BEA: apenas 28% nas Ãreas com solos profundos e 65% nas Ãreas com solos rasos.<br>Regarding ecohydrology, the catchment water is distributed over several important compartments. Many studies in semiarid re gions indicate the surface reservoirs as the main water compartments. However, the watershed has greater scope than the water reservoirs contained therein, and water resources in compartments distributed in the watershed (like in soil) should be analyzed not only with regard to ecological uses, but also as spaces of water availability. Therefore, the object ive of this work was to analyze, based on measurements and modeling, the water dynamics in th e soils of a semi-arid basin in preserved Caatinga, and its impact on water availability. Wit h this in mind, it was measured, among others, the soil moisture, every hour, from 2003 to 2010 (2923 days) in the Aiuaba Experimental Basin (AEB, 12 km Â), fully preserved and with average annual rainfall of 560 mm. Monitoring was carried out through three TDR se nsors, one installed in each of the three soil and vegetation associations (SVA) identified in the basin. The research method considered six main steps: i) assessment of the eff ective root depth of preserved Caatinga ii) calibration of humidity TDR sensors iii) space-time representation of soil moisture in each SVA unit iv) analysis of soil water availability in the root zone, v) parameterization of the WASA-SED hydrological model, and vi) parameterizati on of the DiCaSM hydrological model. The results of this research indicate the importance of addressing the temporal analysis of soil moisture and soil water availability in the root zone to maintain the Caatinga biome. More specifically, it was observed that the effecti ve depth of the root system on AEB ranged between 70 and 80 cm in areas with deep soils, but in areas with shallow soils, it was observed that the effective depth of the roots had adapted to the constraints, having been reduced to less than 40 cm. Furthermore, the season al analysis showed that in the dry season, the roots have lengths up to 11 cm smaller, openin g, therefore, secondary pores that facilitate the penetration of what little rain water falls in the dry months (June-December), as well as in the first rains of the wet season. In the two SVAs whose soils are deep and the vegetation is dense, the soil water is 'not available' (ie below the permanent wilting point - WP) during nearly nine months a year (72% of the time), and on ly during three months of the year (25% of the time) the soil water is available. In the re maining 3% of the year (about 10 days) there is gravitational water in these SVAs. In the SVAs whose soil is shallow and whose vegetation is sparse, the dynamics of soil water are different : the time when there is gravitational water, available and unavailable, is practically the same (four months a year). This is due to, among other things, the low soil moisture at the permanen t wilting point of the Udorthent, and to its limited thickness, generating saturation much more frequently than in others that - unlike this one - have deep drainage. The depletion of soil wat er under conditions of moisture below the wilting point was another important result of this research. In the two associations with deep soils and thick vegetation, it was observed â throu ghout the observation period â continuous fall of moisture level until it approached asymptot ically the residual moisture. More detailed analysis showed that the reduction of soil moisture between the WP and the residual moisture level always followed the exponential decay. It was observed, in the association of shallow soil and sparse vegetation, that the moisture did not fall to below the WP, even subjected to the same rigorous climate of the other associations . Considering: (i) that in such a dry soil, the drainage is unlikely, and (ii) that the associated processes of percolation and evaporation should not be responsible for the removal of soil w ater either (since the phenomenon is not observed in SVAs whose soil is shallow and therefor e warmer) , it is raised the hypothesis that the soil drying under these conditions must be caused by water extraction by vegetation. This would strengthen the argument that the Caating a has adapted to survive under water stress. The hydrological models WASA-SED and DiCaSM failed to adequately represent the temporal dynamics of soil water in the AEB. However , the models did satisfactorily reproduce the retention curves of soil moisture, al lowing the representation of the water availability in the root zone for planning purposes . Finally, we managed to evaluate - quantitatively, spatially and temporally â the soil water availability. This availability is of the same order of magnitude of the availability of an o ptimal surface reservoir. The availability in the soil, in quantitative terms, can be almost five times higher than that of the surface reservoir. However, the security associated with su rface water (90%) is much higher than the water permanence available in the AEB: just 28% in areas with deep soils and 65% in areas with shallow soils.

Cette etude cherche a determiner sous quelles conditions economiques l'eau souterraine peut etre utilisee a des fins agricoles dans le sahel. Auparavant on a cherche a definir la place de l'eau dans la crise de l'agriculture. Puis on a examine le role que l'eau souterraine peut jouer dans la resolution de cette crise

In Sudan, land degradation/desertification (LDD) has devastated large areas and consequently, it includes social, economic, and environmental aspects. LDD results from various factors, including climatic variation and human activities. Probably the LU practices and their changes have contributed to an increase of LDD in that area. Remote sensing technology has become unique and developed tool for providing temporal and spatial information for the LDD research and other environmental aspects. Determination of LDD and its relationship to land use pattern change (LUC) at spatiotemporal scale is rare, critical issue, and is one of the recommended research in semi-arid regions of Sudan. The study was carried out to derive accurate and improved spatiotemporal information: to assess the status of land LDD of vegetation and soil, to assess and model influences of the LUC on LDD, and moreover to analyse the synergistic factors that have caused the land use change and/or LDD in semi- arid zone of Elgeteina Locality in While Nile State, Sudan during the last 36 years, using appropriate remote sensing (RS) and GIS technology. The study used four-cloud free images of different sensors (MSS 1973, TM 1986, ASTER 2009 and TM 2010). The imageries were Geo-referenced and radiometrically corrected by using ENVI-FLAASH software. Then subsets of the study area were taken, ranging from 1600-2000 Km2. The study applied the new approach of integration between vegetation and soil indices and in situ data to assess the LDD. Comparison between pixel based image analysis (PBIA) and latterly approach of object based image analysis (OBIA) was done by selecting the best one for mapping LUC and LDD accurately. The change detection - matrix was applied to estimate the spatiotemporal of changes in land use and land degradation. Moreover, correlation and model approach was employed for fusing the climatic, socioeconomic and remote sensing data to determine the relationships between the different factors and to analyse the reasons for the LUC and LDD as well as for modelling LU effects on LDD. The study revealed that: The changes in land use patterns (RA, FWL and FML) took place in 1973 – 86 – 2009, and affecting thoroughly different patterns of the vegetation cover. Likewise the LUC affected soil degradation which led to the movement of sand dunes in 1973 – 2009. The agricultural activity is the dominant and has more effect on LDD particularly on the vegetation cover degradation. The population growth and the socioeconomic status of local people are the main indirect human inducing factors responsible for LUC and/or LDD. SARVI is slightly more efficient than NDVI, SAVI, ND4-25 and ND42-57, for detecting the vegetation status in semi-arid area, therefore the study selected it for the assessment. GSI proved highly efficient in determining the different types of soil degradation, and in producing the map of top soil grain size, which assisted in the assessment of land degradation and desertification. OBIA-fuzzy logic classification performed better than the PBIA- hybrid classification for assessing LU patterns impact on LDD. The study recommends to: replication of this study by using different imagery with high resolutions and sophisticated software, such as eCognition and Feature Analyst (FA) for increasing the validity and accuracy of the assessment and modelling of LU patterns and LDD status in dry land is important in the Sudan<br>Im Sudan hat Land Degradation/ Desertifikation (LDD) weite Gegenden verwüstet, wobei hierbei soziale, wirtschaftliche und Umweltaspekte eine Rolle spielen. LDD wird von verschiedenen Faktoren ausgelöst, darunter Klimavariationen und menschliche Aktivitäten. Wahrscheinlich haben Landnutzungspraktiken und ihre Änderungen zu erhöhter LDD in der untersuchten Gegend beigetragen. Fernerkundungstechnologien sind sehr gute und weit entwickelte Werkzeuge um zeitliche und räumliche Informationen zur Erforschung von LDD und anderen Umweltaspekten zu ermitteln. Die Bestimmung von LDD und ihre Beziehung zur Änderung von Landnutzungsmustern (LUC) im raum-zeitlichen Maßstab ist bislang noch selten erforscht und ist ein Forschungsbereich, der für die semi-ariden Regionen des Sudan empfohlen wird. Die Studie wurde durchgeführt, um genaue und verbesserte raum-zeitliche Informationen zu gewinnen: um den Status der LDD von Vegetation und Boden zu bewerten, um den Einfluss des Landnutzungswandels auf LDD zu beurteilen und zu analysieren, und außerdem um die synergetischen Faktoren die den Landnutzungswandel und/oder LDD verursacht haben zu analysieren. Dabei wurde die semi-ariden Zone des Elgeteina Gebietes im Staat Weisser Nil (Sudan) während der vergangenen 36 Jahren unter Verwendung von geeigneter Fernerkundungs- und GIS-Technologie untersucht. Für die Studie wurden vier wolkenfreie Bilder von verschiedenen Sensoren (MSS 1973, TM 1986, ASTER 2009 and TM 2010) verwendet. Die Bilder wurden georeferenziert und radiometrische korrigiert, wobei die ENVI-FLAASH Software verwendet wurde. Anschließend wurden Teilgebiete des Untersuchungsgebietes mit einer Größe zwischen 1.600 und 2.000 Km2 ausgewählt. In der Studie fand der neue Ansatz der Integration von Vegetation und Boden Indizes und in-situ Daten Verwendung, um LDD zu bewerten. Ein Vergleich von pixel-basierter Bildanalyse (PBIA) und einem Ansatz von objekt-basierter Bildanalyse (OBIA) wurde durchgeführt, um die beste Methode der Kartierung von LUC und LDD ermitteln. Veränderungsmatrizen wurden eingesetzt, um räumlich-zeitlichen Änderungen der Landnutzung und Land Degradation abzuschätzen. Außerdem wurde ein Korrelation- und Modellierungs-Ansatz eingesetzt, um die klimatischen, sozioökonomischen und Fernerkundungsdaten zu verschmelzen und das Verhältnis zwischen den unterschiedlichen Faktoren zu bestimmen und um die Gründe für LUC und LDD zu analysieren aber auch um die Auswirkungen der Landnutzung auf LDD zu modellieren. Die Studie hat folgendes gezeigt: Die Änderungen der Landnutzungsmuster (RA, FWL and FML) fand in 1973 – 86 – 2009 statt und betraf sehr unterschiedliche Vegetationsmuster. Ebenso hatte die LUC Auswirkungen auf die Bodendegradation, was zu einer Verschiebung von Sanddünen im Zeitraum 1973-2009 führte. Landwirtschaft dominiert und hat starke Auswirkungen auf LDD, insbesondere auf die Degradation der Vegetationsbedeckung. Die Bevölkerungszunahme und der sozioökonomische Status der lokalen Bevölkerung sind die wesentlichen indirekten menschlichen Faktoren die verantwortlich für LUC und/oder LDD sind. SARVI ist etwas effizienter als NDVI, SAVI, ND4-25 und ND42-57, um den Zustand der Vegetation in semi-ariden Gebieten zu bestimmen, deshalb wurde dieser für die Studie ausgewählt. Es stellte sich heraus, dass der GSI hoch-effizient war, sowohl bei der Bestimmung der unterschiedlichen Typen von Bodendegradation als auch bei der Erstellung von Karten der obersten Bodenkorngröße, die bei der Bewertung der Landdegradation und Desertifikation half. OBIA-Fuzzy Logic Classification arbeitete dabei etwas genauer und effizienter als die PBIA-Hybrid Classification, um die Auswirkungen der Landnutzungsmuster auf LDD zu beurteilen. Als Fortsetzung der durchgeführten Arbeiten empfiehlt sich eine nochmalige Durchführung der Studie wobei anderes, hochaufgelöstes Bildmaterial und anspruchsvolle Software, wie eCognition und Feature Analyst (FA) verwendet werden sollten, um die Gültigkeit und Genauigkeit der Bewertungen und Modellierung des LU und LDD Status von Trockenland im Sudan zu beurteilen

Les données de la recharge des aquifères de socle au Sahel en Afrique de l'Ouest sont limitées en raison d'une connaissance insuffisante sur les mécanismes de recharge. Cette étude a été initiée dans le bassin versant à la rivière éphémère de Tougou (37 km2) pour améliorer la compréhension des mécanismes de recharge d'un aquifère de socle dans la zone sahélienne du Burkina Faso. Elle est basée sur des investigations menées de 2016 à 2020 sur un transect piézométrique et des puits de grand diamètre, respectivement perpendiculaires et longitudinaux à la rivière. L'analyse du profil de tomographie de résistivités électriques et des logs des forages, des tests de perméabilité, le traçage à la conductivité électrique et à la température des eaux souterraines, le suivi piézométrique et des hauteurs d'eau dans la rivière ainsi que des mesures pluviométriques ont été entrepris. Les résultats ont montré un aquifère de la saprolite latéralement continu (10-22 m d'épaisseur) surmonté par des sols résiduels sous la rivière et de la latérite discontinue sur les rives. Sous la rivière, la saprolite se trouve au-dessus de l'aquifère localisé dans les schistes légèrement altérés avec une drainance verticale ascendant ou descendant indépendamment des saisons. La saprolite est alimentée par la recharge concentrée au niveau de la rivière et par la recharge diffuse provenant des précipitations sur les rives, selon les informations fournies par les variations des niveaux piézométriques, le traçage des eaux souterraines et la corrélation croisée entre les niveaux piézométriques et les deux sources potentielles de recharge (la pluie et la rivière). Les valeurs de conductivité hydraulique du sol et la présence des argiles dans le profil d'altération indiquent une restriction l'infiltration de la matrice du sol. Ceci qui suggère l'occurrence de la recharge diffuse et concentrée à travers les voies de recharge préférentielles. Pour la période 2018-2020, la méthode de fluctuation des niveaux piézométriques fournit des estimations de recharge de 14-51 mm/an sur la rive gauche, 10-36 mm/an sur la rive droite et 148-194 mm/an dans le lit de la rivière<br>Groundwater recharge rate for weathered rock aquifers in the Sahel of West Africa are sparse due to insufficient knowledge of the recharge pathways. This study was initiated in the Tougou ephemeral river catchment (37 km2) to improve understanding of recharge pathways to a weathered rock aquifer in the dryland of Burkina Faso. It is based on field investigations conducted in 2016–2020 on a piezometric transect and large-diameter wells, perpendicular and longitudinal to the river, respectively. Geophysical measurements, lithologs analysis, permeability tests, measurements of groundwater electrical conductivity and temperature, groundwater and river level monitoring, and rainfall measurements were undertaken. The results showed a laterally continuous saprolite aquifer (10–22 m thick) overlain by residual soils beneath the river and discontinuous laterite on the banks. Below the river, the saprolite overlays the weathered schist aquifer with an upward or downward hydraulic gradient regardless of the seasons. The saprolite is replenished by focused recharge from the river and diffuse recharge from the rainfall on the banks, according to information from the groundwater hydrographs, groundwater tracing results, and cross-correlation between the groundwater levels and the two potential recharge sources (rainfall and river water). The values of soil hydraulic conductivity and the presence of the clay in the soil profile indicate restriction of diffuse and focused recharge through soil matrix infiltration, suggesting there are preferential recharge pathways. For the 2018–2020 period, the water table fluctuation method provides recharge estimates of 14-51 mm/year on the left bank, 10-36 mm/year on the right bank and 148-194 mm/year in the riverbed

This research aims to analyze the environmental potentialities present in the effectiveness of area of organic agriculture in Sergipe Central Arid zone. It appears that the spreading of organic agriculture in Sergipe is taking place thanks to the construction of new social and environmental coexistence level values associated with the changes in management practices. The area of this analysis are the municipalities of Areia Branca, Itabaiana and Malhador, which are part of the territory of Central Sergipe Arid zone. To develop this research the study methodology was structured in three stages: Cabinet, which covers literature research, visiting the agencies and entities for secondary data collection and mapping survey; field step comprises study area observation and recognition, location points marking, semi-structured interviews application and the photographic survey; the last step is called synthesis, since the achieved results in the two previous steps will be analyzed wether the initial study hypothesis is proven or not. This geographical area methodological theoretical model of evaluation is related to the definition / evaluation of potentialities environmental indicators. Thus, the construction of these as instruments of potentialities environmental indicators matrix allowed a simplified and qualitative reading of environmental, social, economic and cultural needs of the study area, showing the organic system new territoriality configuration. Therefore, the analysis concluded that the surveyed municipalities have potentialities features that favor the development of organic farming, however, they also have limitations that contribute to slower growth of organic production in the study area. Thus, the potentialities are environmental sphere related, such as the use of natural resources and the practice of environmental conservation, and also the influence of historical tradition in the production and marketing of foodstuffs in the Arid zone. As for the limitations, they are related to difficulties in the social, economic and political spheres that hinder the full development of organic production.<br>Esta pesquisa objetiva analisar as potencialidades ambientais presentes na área de efetivação da agricultura orgânica no Agreste Central Sergipano. Verifica-se que a disseminação da agricultura orgânica em Sergipe está ocorrendo a partir da construção de novos valores de convivência social e ambiental associados às mudanças das práticas de manejo. O recorte espacial desta análise são os municípios de Areia Branca, Itabaiana e Malhador, que fazem parte do território do Agreste Central Sergipano. Para desenvolver esta pesquisa a metodologia de estudo foi estruturada em três etapas: gabinete, abrange pesquisa bibliográfica, visita a órgãos e entidades para coleta de dados secundários e levantamento cartográfico; a etapa campo compreende a observação e reconhecimento da área de estudo, a marcação de pontos de localização, a aplicação de entrevistas semi-estruturadas e o levantamento fotográfico; a última etapa foi denominada de síntese, uma vez que serão analisados os resultados alcançados nas duas etapas anteriores, comprovada ou não a hipótese inicial deste estudo. O modelo teórico metodológico de avaliação deste espaço geográfico está relacionado com a definição/avaliação de indicadores de potencialidade ambiental. Assim, o uso destes como instrumentos construtivos da matriz de indicadores de potencialidade ambiental permitiu uma leitura simplificada e qualitativa das necessidades ambientais, sociais, econômicas e culturais da área de estudo, evidenciando a configuração de novas territorialidades do sistema orgânico de produção. Logo, a análise concluiu que os municípios pesquisados apresentam características potenciais que favorecem o desenvolvimento do cultivo orgânico, contudo, também apresentam limitações que contribuem para a desaceleração do crescimento da produção orgânica na área de estudo. Assim, as potencialidades relacionam-se à esfera ambiental, a exemplo do uso dos recursos naturais e à prática de conservação ambiental, e, também, à influência da tradição histórica na produção e comercialização de gêneros alimentícios no Agreste. Já as limitações estão relacionadas às dificuldades encontradas nas esferas social, econômica e política que dificultam o pleno desenvolvimento da produção orgânica.