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1
Hakim, Lamia. "Les évolutions dans les opérations de logements sociaux construits à Paris entre 2007 et 2020 face aux exigences énergétiques et environnementales." Electronic Thesis or Diss., Paris 10, 2022. http://www.theses.fr/2022PA100142.
Abstract:
Dans le contexte de la lutte contre le changement climatique, la réduction de la consommation énergétique des bâtiments devient une urgence. À Paris, le secteur du bâtiment représente un enjeu important quant à cet objectif. Plusieurs décisions politiques ont été adoptées afin de réduire les consommations d’énergie et de protéger l’environnement. Parmi ces engagements, figurent le Plan Climat de la Ville de Paris et le Plan Biodiversité. L’objet de cette thèse est d’examiner les transformations que les impératifs environnementaux et les exigences énergétiques liés notamment à ces plans ont entraînées dans les nouvelles opérations de logements sociaux parisiens construits entre 2007 et 2020. C’est pourquoi nous étudions plusieurs « aspects » des constructions (positionnement sur la parcelle, morphologie, prolongements extérieurs, végétalisation, typologie et organisation spatiale, rapport entre l’intérieur et l’extérieur du logement, système constructif et enveloppe). La méthodologie de cette recherche est principalement basée sur des entretiens semi-directifs menés auprès des architectes des agences d’architecture impliquées dans la réalisation d’opérations de logements sociaux à Paris et sur des analyses de plans. Cette thèse met en évidence, au cours des années 2010, une première phase d’évolution des logements sociaux au regard de la prise en compte des enjeux environnementaux et énergétiques dans la conception de ces logements. Elle annonce les prémices de transformations actuelles plus radicales, tant dans la spatialité des appartements, les rapports aux sites et les typologies que dans les modes de construction des logements sociauxIn the fight against climate change, reducing the energy consumption of buildings is becoming an emergency. In Paris, the building sector poses a significant challenge to achieving the objective of reducing buildings’ energy consumption. Several political commitments have been made to reducing energy consumption and protecting the environment. These commitments include the City of Paris Climate Plan and the Biodiversity Plan. The purpose of this thesis is to examine the transformations that environmental imperatives and energy requirements, which are associated with the abovementioned plans in particular, brought about in the Parisian social housing facilities built between 2007 and 2020. Hence, in this thesis, we study several aspects of construction (positioning on the plot, morphology, exterior extensions, vegetation, typology and spatial organization, the relationship between the dwelling’s interior and exterior, and the construction system and envelope). This research’s methodology was mainly based on semi-structured interviews conducted with architectural agencies involved in the construction of social housing facilities in Paris and on the analyses of plans. The content of this thesis highlights an initial phase in the evolution of social housing with regard to the consideration of environmental and energy issues in the design of housing units in the 2010s. This thesis constitutes the basis for more radical current transformations in the spatiality of the apartments, the buildings’ relationships with the sites and typologies, and the methods of constructing social housing
2
Zupan, Laure. "Au-delà des espèces, comment protéger simultanément l'histoire évolutive, le fonctionnement des écosystèmes et les services procurés par la nature." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENV063/document.
Abstract:
La biodiversité est définie comme la variété et la variabilité du monde vivant sous toutes ses formes. Elle est souvent appréhendée par la richesse en espèces. Pourtant il existe d'autres « facettes » de la biodiversité (telles que la diversité phylogénétique et fonctionnelle) qui sont à considérer pour comprendre la plupart des processus évolutifs et écologiques. Aujourd'hui, la prise en compte de ces différentes facettes ainsi que les services des écosystèmes –bénéfices que les humains retirent directement des écosystèmes – sont au cœur de l'agenda européen de la conservation. Cependant pour mettre en place de nouvelles actions, une meilleure compréhension des variations spatiales de ces différentes facettes et de leurs relations avec les services des écosystèmes est nécessaire. Ce travail visait à quantifier, décrire et comprendre la distribution de la richesse spécifique et de la diversité phylogénétique et fonctionnelle des tétrapodes d'Europe et leurs liens avec les services écosystémiques. L'étude des patrons spatiaux de la diversité phylogénétique pour différents groupes taxonomiques a montré une absence de recouvrement, une protection inégale et a permis d'identifier des zones particulières d'histoire évolutive indétectables par le prisme unique de la richesse spécifique. Alors que les facteurs environnementaux liés au climat (comme la température ou la productivité primaire) semblent être prépondérant pour expliquer la distribution de chaque facette de diversité, leurs influences respectives varient selon la facette considérée. Enfin, la comparaison de différents scénarios de conservation dans lesquels plus d'importance est donnée soit à la protection de la biodiversité soit à celle des services écosystémiques a mis en avant des relations complexes (synergies et compromis) et non prédictibles mettant en évidence les enjeux liés à la protection simultanée de plusieurs groupes d'espèces, plusieurs facettes de diversité et d'un éventail de services écosystémiquesBiodiversity is defined as the variety and variability of living organisms on Earth and is often measured through species richness. However, biodiversity is composed of other facets (e.g. phylogenetic and functional diversity) that need to be considered to account for evolutionary and ecological processes. Considering these multiple facets of biodiversity together with ecosystem services – direct benefit human obtain from nature – is central in the European conservation agenda. However, to propose new planning strategies, a better understanding of the spatial variation of these different facets and their relationships to ecosystem services is crucial. The objective of this Ph. D. project was to better quantify, describe and understand the spatial variation of different biodiversity facets and analyse their links to ecosystem services. The study of spatial pattern of phylogenetic diversity showed a low overlap between the different taxonomic groups and an unequal protection within the current European protected areas system. This analysis allowed identifying areas of particular evolutionary history, which would be undetectable through the unique lens of species richness. Although environmental factors related to climate (e.g. temperature, primary productivity) seemed to best explain each facet, their relative importance varied across biodiversity facets. Finally a comparison of conservation scenarios where priority was given either to protecting biodiversity protection or to protecting ecosystem services highlighted complex and unpredictable relationships (synergies and trade-offs) and stressed out the stakes linked to the simultaneous protection of different facets of diversity of multiple taxonomic groups and a set of ecosystem services
3
Chan, Tin-yau, and 陳天佑. "Hong Kong biodiversity museum." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1994. http://hub.hku.hk/bib/B3198194X.
4
Akhani, Hossein. "Plant biodiversity of Golestan National Park, Iran /." Linz : Biologiezentrum des OÖ. Landesmuseum, 1998. http://www.gbv.de/dms/bs/toc/246607068.pdf.
5
Joyce, Christopher Brian. "Management of European floodplain grasslands for plant biodiversity." Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/6988.
Abstract:
European floodplain grasslands are characterized by periodic flooding and regular management, usually cutting and grazing as part of an agricultural system. Past losses and ecological degradation have been due largely to river regulation and either agricultural intensification or abandonment and have resulted in a substantial reduction in area across Europe. Nevertheless, the remaining resource supports considerable biodiversity and a high level of biological production. A better quantitative understanding of the functioning of these grasslands is required in order to establish effective conservation management within a sustainable land use system. The thesis examines the impact of key management factors on three important functional characteristics of the biodiversity of floodplain plant communities, namely plant diversity (measured by species diversity), cover (%) and primary production (above-ground biomass), on two floodplain grasslands of the River Trent, UK and a third on the the Luznice river, the Czech Republic. Field investigations of the effects of cutting, grazing, cessation of management, the influence of floodborne litter, and the impact of fertilizer nitrogen were undertaken over periods of between one and three seasons. These demonstrated that floodplain grassland plant communities are sensitive to variations in management and that impacts on communities are mediated particularly through effects on plant competition. Productive competitive species were encouraged both by abandonment and fertilizer application whereas cutting and grazing management, and the imposition of litter, favoured stress-tolerating perennials. Species diversity decreased both with high inputs of litter and additions of fertilizer. Plant community responses and competitive strategies of key species are discussed in the context of biodiversity conservation, ecological restoration and management of European floodplain grasslands.
6
Laycock, Helen Fiona. "Evaluating the effectiveness and efficiency of conservation : the UK biodiversity action plan." Thesis, University of York, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.495887.
7
Ingwersen, Sarah. "Biodiversity and forest management, five forest management plans evaluated." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ60848.pdf.
8
Van, Mechelen Carmen. "Nature as a template for a new concept of extensive green roofs." Thesis, Avignon, 2015. http://www.theses.fr/2015AVIG0334/document.
Abstract:
Au cours de notre ère dite « Anthropocène » et caractérisée par l’urbanisation, la biodiversité est fortement contrainte. Il s’agit d’un problème important car elle est considérée comme le principal moteur du fonctionnement des écosystèmes et comme une source de services écosystémiques. Les toits verts sont un exemple de nouveaux écosystèmes au sein de l’environnement urbain. Ils constituent de nouveaux habitats et peuvent alors limiter la perte de biodiversité en ville. Ils offrent de plus d’autres services écosystémiques comme la régulation thermique, la gestion des eaux pluviales, ainsi qu’une certaine valeur esthétique. Dans cette thèse, nous mettrons notamment l’accent sur les toits verts dit "extensifs" (profondeur du substrat < 20 cm) car ils ont une gamme d'applications plus large et sont plus durables (car autonomes et nécessitant donc moins de maintenance).Dans l’Europe du Sud (région Méditerranéen), les performances des toits verts extensifs sont plutôt faibles, probablement à cause de l'effet des fortes températures et de la sécheresse estivale. On peut même s’attendre à une augmentation du niveau de stress des végétaux des toits verts à cause du changement climatique. La mise en place de systèmes d’irrigation pourrait alors aider en favorisant la croissance des plantes et leur survie. Cependant, cet aménagement est souvent perçu comme une option non soutenable car l'accès à l’eau est limité en région méditerranéenne. Au cours de la période estivale, la pénurie d’eau sera de plus encore plus grave du fait du changement climatique. Par conséquent, une augmentation du nombre de recherches menées sur ce sujet est nécessaire afin de sélectionner les espèces végétales les plus adaptées aux toits verts extensifs non irrigués. Il est également nécessaire d’adapter les éléments structurels des toits extensifs pour mieux répondre aux exigences de ces plantes. Pour les pays plus au nord, avec des climats plus froids (par exemple en climat tempéré maritime), les scénarios de changements climatiques prévoient également une augmentation des températures et des précipitations plus erratiques. Les entreprises de toits végétalisés dans ces régions bénéficieront donc également des résultats d’une telle recherche.L’objectif principal de cette thèse était d’élaborer et de tester un nouveau concept pour la réalisation de toits verts extensifs, comprenant notamment la sélection de la végétation et des éléments de structure (substrat). Le travail est basé sur l’hypothèse de « l’habitat modèle », qui énonce qu’il faut cibler les habitats naturels possédant des caractéristiques similaires aux toits verts extensifs afin de trouver des espèces végétales les plus appropriées. La biodiversité en région Méditerranéenne est très riche et il y a plusieurs habitats qui ressemblent plus au moins aux conditions des toits verts extensifs (sols calcaires et superficielles, drainage rapide, pauvreté en nutriments, fluctuations de température, vents forts). Notre hypothèse est alors qu’il serait possible de trouver des plantes possédant des potentiels pour être introduites sur des toits verts extensifs. Parce que la région Méditerranéenne est très étendue, le sud de la France a été sélectionné comme région d’études. Nous concluons que la végétation méditerranéenne peut être une source d'inspiration pour le développement et l’amélioration de la conception des toits verts extensifs, que ce soit pour le climat méditerranéen actuel ou pour d’autres climats sous l'effet futur des changements climatiques prévus. Un choix de plantes appropriées est alors essentiel, ainsi que la conception en termes de techniques d’irrigation durable, de profondeur et composition du substrat et aussi des possibilités de rétention de l’eau. De plus, il existe encore de nombreuses voies pour la réalisation de recherches supplémentaires qui contribueront à la mise en place de toits verts avec une biodiversité plus importanteIn an era of urbanization, biodiversity is under pressure more than ever. Biodiversity is considered a major driver of ecosystem functioning and the provision of ecosystem services. Green roofs, a prime example of urban novel ecosystems, offer habitats and can hence mitigate some biodiversity loss in cities. Apart from biodiversity, green roofs also offer other ecosystem services, such as thermal regulation, stormwater management, and aesthetic and amenity value. Here we focused on extensive green roofs (substrate depth < 20 cm) as these can be applied widely and are more durable (i.e. less maintenance, self-sustaining). In southern Europe (Mediterranean), the performance of (extensive) green roofs is rather low, probably due to the elevated temperatures and summer drought. One may expect that plant stress on green roofs will further increase as a result of climate change. Irrigation could help plant growth and survival. However, irrigation is often perceived as an unsustainable practice, as water is already a limiting factor in many regions and climate change will lead to an even more severe water scarcity during summer. Therefore, research is needed to select plant species suitable for Mediterranean (unirrigated) extensive green roofs, and to adapt green roof design to meet the requirements of the selected plant species. More northern countries with colder climates (e.g. temperate maritime climate) will also face higher temperatures and erratic precipitation events as a result of climate change. The green roof industries located in these regions will hence also benefit from the outcome of such research. The main goal of this thesis was to elaborate and test a new concept for extensive green roof design, comprising both plant selection and design elements. The work is based on the habitat template theory, which states that natural habitats with similar characteristics as extensive green roofs should be targeted when searching for suitable plant species. Mediterranean regions are a hotspot of biodiversity and contain many habitats that match to some extent the conditions on extensive green roofs (e.g. shallow, free draining, nutrient poor and calcareous soils, high temperature fluctuations, windy). We hence hypothesized that it would be possible to find potential plant species for use on extensive green roofs. Because of practical reasons we selected the southern part of France as study region. At the end of this thesis, we conclude that natural habitats in the Mediterranean region can definitely inspire us as a source for development and improvement of extensive green roof design, whether this is for the current Mediterranean climate itself or for other climates under predicted climate change. Appropriate vegetation choice is essential, as well as the design in terms of sustainable irrigation techniques, appropriate substrate depth and composition, and water retention possibilities. Finally suggestions for further research were made
9
Burton, Hazel M. C. "Conservation ecology of biodiversity action plan listed reed beetles of the genus 'Donacia'." Thesis, University of Sussex, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421726.
10
Schulz-Burgdorf, Ulrich. "Habari za miti na mitishamba miongoni mwa Wamijikenda na Waswahili-matokeo ya kwanza kutoka utafiti." Universitätsbibliothek Leipzig, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-98191.
Abstract:
Utafiti ambao ni msingi wa habari hizo umefanywa katika miezi za Oktoba mpaka Disemba 2000 katika wilaya wa Kwale na Kilifi huko nchi ya Kenya. Wanachama wa timu ya utafiti wetu walikuwa Prof. F. Rottland, ambaye aliweka taratibu msamiati wa miti uliokusanywa, na Bw. Mohamed Pakia ambaye ni mwanabiolojia na aliyehojiana wanafunzi wa shule ya sekondari kuhusu ujuzi wa miti na mitishamba wao. Bw. Pakia ameshafanya kazi katika Coastal Forest Conservation Unit, yaani watu ambao husaidia wazee wa kimijikenda katika kuhifadhi misitu mitakatifu inayoitwa \"makaya\" na inatumiwa kwa matambiko na kama makaburi. Bw. Pakia ametambua: Ni hatari ya kupoteza ujuzi wa miti na mitishamba iliyotumiwa nanma ya kimila miongoni mwa wanafunzi wa shule ya sekondari: vijana hawajui matumizi ya mimea na pia wamepotea moyo wa kutaka kujua mambo hayo. Katika habari zifuatazo ninatoa mifano ya ule ujuzi wa watu wazima na wazee.
11
Smith, Ross L. "Invasive alien plant species of The Bahamas and biodiversity management." Miami University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=miami1275062320.
12
Perron, Mary Ann. "The Value of Urban Ponds for Odonata and Plant Biodiversity." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/40522.
Abstract:
Urbanization involves the conversion of natural areas to impervious surfaces, which can lead to an increase in the frequency and severity of flood events in cities. To mitigate flood risk, stormwater ponds are constructed to manage urban runoff. Stormwater ponds can also be colonized by wildlife, but their suitability as habitat is disputed due to potential toxicological risks. This study assessed the suitability of stormwater ponds as habitat for the bioindicators Odonata (dragonflies and damselflies) and determined environmental factors that impact their community structure. Odonata (adults, nymphs and exuviae) were sampled at 41 stormwater ponds and 10 natural reference ponds across the National Capital Region of Canada, with a subset of ponds sampled over four years (2015-2018). Plant communities, water quality and surrounding land cover were analyzed at each pond to determine their impacts on Odonata community structure. Overall, stormwater ponds had lower Odonata abundance and a greater variation in species richness and community structure compared to natural ponds but had comparable dragonfly reproduction rates. Plants were the most significant driver of Odonata communities, as stormwater ponds with a high richness of native wetland plants had higher Odonata abundance and community structures similar to natural ponds. Water quality was the second most important driver of Odonata communities with dragonflies showing greater sensitivity to urban contaminants than damselflies. While stormwater ponds had higher concentrations of trace elements than natural ponds (e.g. Ni, V, As), concentrations were generally below toxic levels for all elements except copper and chloride, the latter likely an input from winter road salting. Surrounding land cover was the least important factor affecting Odonata communities. In conclusion, this research demonstrated the importance of local-scale factors related to plants and water quality in sustaining Odonata communities and specifies recommendations for stormwater pond design and maintenance that enhance urban biodiversity.
13
Van, der Vyver Marius Lodewyk. "Restoring the biodiversity of canopy species within degraded spekboom thicket." Thesis, Nelson Mandela Metropolitan University, 2011. http://hdl.handle.net/10948/1564.
Abstract:
I investigated the return of plant canopy diversity to degraded spekboom thicket landscapes under restoration treatment. I attempted the reintroduction of five nursery propagated and naturally-occurring plant species in severely degraded Portulacaria afra Jacq. (spekboom) dominated thickets that have been subjected to a restoration method involving the planting of dense rows of P. afra truncheons for various time periods and also in degraded and intact thickets. I also planted nursery propagated P. afra cuttings. An average of 30 propagules of each species, were planted in each of the chosen areas in two distinct seasons that exhibited distinct rainfall peaks. Sixteen propagules of P. afra were also planted in each treatment only once. Propagules of the two thicket woody canopy species (S. longispina and P. capensis) showed a total survival of 1% and 9%, respectively. Survival of L. ferocissimum and R. obovatum was 19% and 70% and all propagules of P. afra survived. Analyses showed that survival is primarily tied to a species effect, with R. obovatum and P. afra showing significantly better survival than the other species. Within the other surviving few species a significant preference for overhanging canopy cover was observed. The results show little significance of restoration treatment for propagule survival, suggesting that a range of conditions is needed for the successful establishment of canopy species that likely involves a microclimate and suitable substrate created by canopy cover and litter fall, combined with an exceptional series of rainfall events. I found that the high costs involved with a biodiversity planting endeavour, and the low survival of propagules of thicket canopy plant species (P. afra excepted), renders the proposed biodiversity planting restoration protocol both ecologically and economically inefficient. Restoration success involves the autogenic regeneration of key species or functional groups within the degraded ecosystem. Heavily degraded spekboom-dominated thicket does not spontaneously regenerate its former canopy species composition and this state of affairs was interpreted in terms of a state-and-transition conceptual model. Floristic analyses of degraded, intact and a range of stands under restoration treatment for varying time periods at two locations in Sundays Spekboomveld revealed that the stands under restoration are progressively regenerating canopy species biodiversity with increasing restoration age, and that intact sites are still the most diverse. The high total carbon content (TCC) measured within the older restored stands Rhinosterhoek (241 t C ha-1 after 50 years at a depth of 50 cm) rivals that recorded for intact spekboom thickets, and the number of recruits found within older restored sites rivals intact sites sampled. 2 The changes recorded in the above- and belowground environments potentially identify P. afra as an ecosystem engineer within spekboom dominated thickets that facillitates the build-up of carbon above- and belowground and the accompanying changes in soil quality and the unique microclimate aboveground, which enables the hypothetical threshold of the degraded state to be transcended. This restoration methodology is accordingly considered efficient and autogenic canopy species return was found to be prominent after a period of 35-50 years of restoration treatment.
14
Ali, Nadine. "Communautés de nématodes phytoparasites associés à l'olivier : réponse aux forçages anthropiques et environnementaux." Thesis, Montpellier, SupAgro, 2015. http://www.theses.fr/2015NSAM0015/document.
Abstract:
Les interventions humaines de plus en plus fréquentes et persistantes dans les écosystèmes d'une part, et l'intensification des systèmes de cultures d'autre part qui s'accompagne pour partie de méthodes radicales pour combattre les bio-agresseurs des cultures, nous posent de multiples questions au sujet des risques écologiques liés aux changements des milieux, dont les perturbations induites sur les communautés d'organismes vivants. Les nématodes phytoparasites (NPP), vers ronds microscopiques telluriques qui occasionnent des pertes de production végétale importantes, sont partout présents en communautés. Ces nématodes répondent rapidement aux forçages extérieurs (e.g. anthropiques et environnementaux) par des modifications de la structure de leurs communautés. Par ce travail de thèse, nous cherchons à mieux comprendre l'effet des facteurs impliqués dans l'assemblage des espèces de NPP en communautés associées à l'olivier méditerranéen et à déterminer la réponse de ces communautés aux forçages imposés par la domestication de l'olivier, par l'intensification de sa culture et par différents facteurs environnementaux. L'étude a été réalisée au Maroc dans toutes les régions oléicoles (vergers traditionnels à faible densité et vergers à haute-densité), dans les zones refuge d'olivier sauvage (oléastre) et sur olivier féral. Les facteurs pédoclimatiques qui caractérisent les sites d'échantillonnage ont également été pris en considération. L'analyse de la nématofaune a révélé d'une grande diversité spécifique, de nombreuses espèces étant décrites pour la première fois sur olivier, et une nouvelle espèce (Meloidogyne spartelensis) ayant été découverte. La diversité, la composition taxonomique, trophique et fonctionnelle, la dominance des taxons, les patrons de communautés sont fortement affectés par les différents forçages pris en compte. Le gradient d'anthropisation croissante (sauvage vs féral vs cultivé traditionnel vs cultivé haute-densité) est la variable qui impacte le plus la diversité par réduction de la richesse spécifique et l'augmentation de l'abondance en NPP. L'étude a également porté une attention particulière sur la diversité des nématodes à galles des racines du genre Meloidogyne, un des principaux ravageurs de l'olivier. Elle a indiqué la dispersion de M. javanica dans les vergers et sur olivier féral, alors que d'autres espèces (M. arenaria, M. hapla et M. spartelensis) sont confinées dans les zones refuge des oléastres. Afin d'analyser la diversité génétique, des marqueurs morphologiques et moléculaires ont dévoilé d'une diversité importante entre et au sein des différentes populations de Meloidogyne. Les études diligentées dans le cadre de cette thèse confirment que la diversité et la structure des communautés de NPP pourraient être des indicateurs pertinents pour évaluer la santé des sols dans les agro et écosystèmes, en corrélant diversité et pathogénicité des communautés. Elles soulignent donc l'importance de la diversité parasitaire comme variable prioritaire à prendre en compte pour inspirer des stratégies de gestion des parasites basées sur le concept de résilience de la diversité (même s'il s'agit de parasites), pour une gestion durable des communautés de NPP et la préservation des milieuxHuman activities increasingly frequent and persistent in ecosystems on one hand, and cropping system intensification on the other hand partly with radical methods to control pests and diseases of crops, raise questions about the ecological risks related to biotop changes, including disturbances of living organism communities. Plant-parasitic nematodes (PPN), microscopic round soil-borne worms that cause significant losses of crop production, are everywhere present in communities. They respond quickly to external forces (e.g. human and environmental) by changing the structure of their communities. In this thesis, we seek to better understand the effect of the factors involved in the assemblage of PPN species in communities associated with the Mediterranean olive tree and to determine the response of these communities to forces imposed by olive domestication, by crop intensification and by various environmental factors. The study was conducted in all olive-growing regions in Morocco (traditional low density and high density orchards), in refugia areas for wild olive (oleaster) and on feral olive trees. The soil and climatic factors that characterize the sampling sites were also considered. The analysis of the nematofauna revealed a wide species diversity, many species being described for the first time on olive tree, and a new species (Meloidogyne spartelensis) have been discovered. The diversity, the species / trophic / functional structure of the communities, the dominance of the taxa, and the community patterns are strongly affected by the various forces considered. The increasing anthropogenic gradient (wild vs feral vs traditional cultivation vs high-density cultivation) is the variable that mostly impacts the diversity by reducing the species richness and increasing the abundance of PPN. A particular attention was attributed in this study to the diversity of root-knot nematodes Meloidogyne, a major pest of the olive tree. It revealed that M. javanica is widespread in orchards and olive feral, while other species (M. arenaria, M. hapla and M. spartelensis) are confined in oleaster refuge areas. In order to analyse the genetic diversity, morphological and molecular markers have revealed a significant diversity between and within different Meloidogyne populations. These thesis studies confirm that both the diversity and the structure of the PPN communities could be relevant indicators to assess soil health in agro and ecosystems, by correlating diversity and pathogenicity of communities. They therefore emphasize the importance of parasite diversity as a main variable to consider for inspiring pest control strategies based on the concept of diversity resilience (even if it concerns parasites) for sustainable management of PPN communities and for environment preservation
15
Schmidtke, Andrea. "Biodiversity effects on the performance of terrestrial plant and phytoplankton communities." Phd thesis, Universität Potsdam, 2009. http://opus.kobv.de/ubp/volltexte/2009/3893/.
Abstract:
Die Ökosysteme unserer Erde sind durch das rasante Artensterben infolge von Umweltveränderungen durch den Menschen und des globalen Klimawandels stark betroffen. Mit den Auswirkungen dieses Artenverlustes und der damit einhergehenden Veränderung der Diversität beschäftigt sich die heutige Biodiversitätsforschung. Spezieller wird der Effekt der Diversität auf Ökosystemprozesse wie beispielsweise den Biomasseaufbau von Primärproduzenten oder der Resistenz einer Gemeinschaft gegen die Einwanderung neuer Arten untersucht. Die Quantifizierung des Einflusses der Diversität auf die Primärproduktion und das Verständnis der zugrunde liegenden Mechanismen ist von besonderer Wichtigkeit. In terrestrischen Pflanzengemeinschaften wurde bereits ein positiver Diversitätseffekt auf die Gemeinschaftsbiomasse beobachtet. Dies wird hauptsächlich durch den Komplementaritäts- und/oder den Dominanzeffekt erklärt. Die Komplementarität zwischen Arten ist beispielsweise bei Unterschieden in der Ressourcenausnutzung gegeben (z.B. unterschiedliche Wurzeltiefen). Diese kann zu einer besseren Nährstoffausnutzung in diverseren Gemeinschaften führen, die letztlich deren höhere Biomassen erklärt. Der Dominanzeffekt hingegen beruht auf der in diverseren Gemeinschaften höheren Wahrscheinlichkeit, eine hochproduktive Art anzutreffen, was letztlich die höhere Biomasse der Gemeinschaft verursacht.
Diversitätseffekte auf Ökosystemprozesse wurden bisher hauptsächlich auf der Gemeinschaftsebene untersucht. Analysen über die Reaktionen, die alle Arten einer Gemeinschaft einschließen, fehlen bisher. Daher wurde der Einfluss der Diversität auf die individuelle Performance von Pflanzenarten innerhalb des Biodiversitätsprojektes „Das Jena Experiment“ untersucht. Dieses Experiment umfasst 60 Arten, die charakteristisch für Mitteleuropäische Graslandschaften sind. Die Arten wurden in die 4 funktionellen Gruppen Gräser, kleine Kräuter, große Kräuter und Leguminosen eingeteilt. Im Freilandversuch zeigte sich, dass mit steigender Artenzahl die individuelle Pflanzenhöhe zunahm, während die individuelle oberirdische Biomasse sank. Der positive Diversitätseffekt auf die pflanzliche Gemeinschaftsbiomasse kann folglich nicht auf der individuellen oberirdischen Biomassezunahme beruhen. Überdies reagierten die einzelnen funktionellen Gruppen und sogar die einzelnen Arten innerhalb einer funktionellen Gruppe unterschiedlich auf Diversitätsveränderungen. Folglich ist zu vermuten, dass einige Ökosystemprozesse auf Gemeinschaftsebene durch die Reaktionen von bestimmten funktionellen Gruppen bzw. Arten hervorgerufen werden.
Diversitätseffekte auf Gemeinschaftsbiomassen wurden bislang hauptsächlich mit terrestrischen Pflanzen und weniger mit frei-schwebenden Algenarten (Phytoplankton) erforscht. Demzufolge wurde der Einfluss der Diversität auf die Biomasse von Phytoplankton-Gemeinschaften experimentell untersucht, wobei es sowohl zu negativen als auch positiven Diversitätseffekten kam. Eine negative Beziehung zwischen Diversität und Gemeinschaftsbiomasse zeigte sich, wenn schnell-wüchsige Algenarten nur geringe Biomassen in Mono- und Mischkultur aufbauten. Die vorhandenen Nährstoffe in der Mischkultur wurden von den schnell-wüchsigen Arten monopolisiert und folglich standen sie den langsam-wüchsigen Algenarten, welche viel Biomasse in Monokultur aufbauten, nicht mehr zur Verfügung. Zu einem positiven Diversitätseffekt auf die Gemeinschaftsbiomasse kam es, wenn die Artengemeinschaft eine positive Beziehung zwischen Wachstumsrate und Biomasse in Monokultur zeigte, sodass die schnell-wüchsige Algenarten viel Biomasse aufbauten. Da diese schnell-wüchsigen Algen in der Mischkultur dominant wurden, bestand die Gemeinschaft letztlich aus hoch-produktiven Algenarten, was zu einer erhöhten Gesamtbiomasse führte. Diese beiden Versuchsansätze verdeutlichen Mechanismen für die unterschiedlichen Reaktionen der Gemeinschaften auf Diversitätsveränderungen, welche auch für terrestrische Pflanzengemeinschaften gefunden wurden.
Ein anderer wichtiger Ökosystemprozess, der von der Diversität beeinflusst wird, ist die Anfälligkeit von Gemeinschaften gegenüber invasiven Arten (Invasibilität). Die Invasibilität wird von einer Vielzahl von Faktoren beeinflusst und demzufolge wurde der Effekt der Diversität und der Produktivität (Nährstoffgehalt) auf die Invasibilität von Phytoplankton-Gemeinschaften in An- und Abwesenheit eines Herbivoren untersucht. Die zwei funktionell unterschiedlichen invasiven Arten waren die Blaualge Cylindrospermopsis raciborskii (schlecht fressbar) und der Phytoflagellat Cryptomonas sp. (gut fressbar). Es zeigte sich, dass der Fraßdruck, welcher selber durch die Produktivität beeinflusst wurde, einen bedeutenden Effekt auf die Invasibilität von Phytoplankton-Gemeinschaften hat. Die funktionellen Eigenschaften der invasiven und residenten Arten waren zudem bedeutender als die Artenzahl.To date, positive relationships between diversity and community biomass have been mainly found, especially in terrestrial ecosystems due to the complementarity and/or dominance effect. In this thesis, the effect of diversity on the performance of terrestrial plant and phytoplankton communities was investigated to get a better understanding of the underlying mechanisms in the biodiversity-ecosystem functioning context. In a large grassland biodiversity experiment, the Jena Experiment, the effect of community diversity on the individual plant performance was investigated for all species. The species pool consisted of 60 plant species belonging to 4 functional groups (grasses, small herbs, tall herbs, legumes). The experiment included 82 large plots which differed in species richness (1-60), functional richness (1-4), and community composition. Individual plant height increased with increasing species richness suggesting stronger competition for light in more diverse communities. The aboveground biomass of the individual plants decreased with increasing species richness indicating stronger competition in more species-rich communities. Moreover, in more species-rich communities plant individuals were less likely to flower out and had fewer inflorescences which may be resulting from a trade-off between resource allocation to vegetative height growth and to reproduction. Responses to changing species richness differed strongly between functional groups and between species of similar functional groups. To conclude, individual plant performance can largely depend on the diversity of the surrounding community. Positive diversity effects on biomass have been mainly found for substrate-bound plant communities. Therefore, the effect of diversity on the community biomass of phytoplankton was studied using microcosms. The communities consisted of 8 algal species belonging to 4 functional groups (green algae, diatoms, cyanobacteria, phytoflagellates) and were grown at different functional richness levels (1-4). Functional richness and community biomass were negatively correlated and all community biomasses were lower than their average monoculture biomasses of the component species, revealing community underyielding. This was mainly caused by the dominance of a fast-growing species which built up low biomasses in monoculture and mixture. A trade-off between biomass and growth rate in monoculture was found for all species, and thus fast-growing species built up low biomasses and slow-growing species reached high biomasses in monoculture. As the fast-growing, low-productive species monopolised nutrients in the mixtures, they became the dominant species resulting in the observed community underyielding. These findings suggest community overyielding when biomasses of the component species are positively correlated with their growth rates in monocultures. Aquatic microcosm experiments with an extensive design were performed to get a broad range of community responses. The phytoplankton communities differed in species diversity (1, 2, 4, 8, and 12), functional diversity (1, 2, 3, and 4) and community composition. The species/functional diversity positively affected community biomass, revealing overyielding in most of the communities. This was mainly caused by a positive complementarity effect which can be attributed to resource use complementarity and/or facilitative interaction among the species. Overyielding of more diverse communities occurred when the biomass of the component species was correlated positively with their growth rates in monoculture and thus, fast-growing and high-productive species were dominant in mixtures. This and the study mentioned above generated an emergent pattern for community overyielding and underyielding from the relationship between biomass and growth rate in monoculture as long as the initial community structure prevailed. Invasive species can largely affect ecosystem processes, whereas invasion is also influenced by diversity. To date, studies revealed negative and positive diversity effects on the invasibility (susceptibility of a community to the invasion by new species). The effect of productivity (nutrient concentration ranging from 10 to 640 µg P L-1), herbivory (presence/absence of the generalist feeder) and diversity (3, 4, 6 species were randomly chosen from the resident species pool) on the invasibility of phytoplankton communities consisting of 10 resident species was investigated using semi-continuous microcosms. Two functionally diverse invaders were chosen: the filamentous and less-edible cynaobacterium C. raciborskii and the unicellular and well-edible phytoflagellate Cryptomonas sp. The phytoflagellate indirectly benefited from grazing pressure of herbivores whereas C. raciborskii suffered more from it. Diversity did not affect the invasibility of the phytoplankton communities. Rather, it was strongly influenced by the functional traits of the resident and invasive species.
16
Oikawa, Junko. "Future role of living plant collections in gardens for biodiversity conservation." Thesis, University of Reading, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314314.
17
Harper, Leah Wheelbarger. "Plant Biodiversity across Three Successional Stages in Forests of Southern Illinois." OpenSIUC, 2020. https://opensiuc.lib.siu.edu/theses/2794.
Abstract:
Since the time of European settlement, land-use history, management practices, the introduction of non-native invasive species (NNIS), and climate change have dramatically changed the successional pathways of Southern Illinois forests. Biodiversity is considered essential for ecosystem health and resiliency, so understanding the impact theses forest changes have on biodiversity is necessary to guide future management decisions. This study was conducted at Touch of Nature Environmental Center (TONEC) in Southern Illinois using the Shannon diversity index (H') to compare the levels of biodiversity in the overstory, shrub, seedling, and herbaceous layers across early, mid, and mature successional stages. Twenty plots were randomly placed within early, mid, and mature forest successional stages for a total of 60 plots. Four circular nested vegetation plots were recorded at each plot location. In the overstory plots (area 314.16 m2), woody stems above 6.5 cm diameter at breast height (dbh), age class, and crown were all recorded. In the shrub layer (area 28.27 m2), all woody stems between 2.5 and 6.5 cm dbh were recorded, while in the seedling layer (area 3.14 m2), all woody stems < 1 cm dbh were recorded. In the herbaceous layer, (area 1 m2) species were measured by percent cover. Shannon diversity index (H') was calculated for each plot. When vegetation layers were combined and mean H' within forest successional stages were compared, no differences were found. However, when successional stages were combined within each vegetation layer, the shrub layer had the least H' increasing to seedling, increasing again to overstory and herbaceous; these being equal. When breaking down the vegetation layers separately and comparing H' across successional stages within each, both the overstory and shrub layers had no difference. Early successional was the least diverse in seedling, rising to mid and mature, which were equal. The herbaceous layer showed an opposite trend with early having the highest H' decreasing to mid and decreasing again to mature. Finally looking at the differences across vegetation layers within early, mid, and mature successional stages. Early-successional had the most variability with the highest H' in herbaceous; this decreased progressively to overstory then to shrub and seedling, which were equal. In mid-successional plots, overstory, seedling, and herbaceous layers were equal with H' decreasing in shrub. In mature plots, all vegetation layers had the same H'. Across all vegetation layers, the highest percentage of NNIS was in early-successional, followed by mid, with notably less found in mature forest. Even in instances where H' values were the same, species composition across forest successional stages were quite different. While overall biodiversity is the same across successional stages, differences in H' can be seen when looking at the vegetation layers. Management should focus on removing NNIS in the early and mid-successional forests paying particular attention to the shrub layer, which has the overall lowest H' with the most dramatic differences in composition and the presence of NNIS across all successional stages. Also of concern is the low H' in the seedling layer in early-successional forest, which reduces the likelihood of successful regeneration of these hardwood stands in the future.
18
Neloy, Md Naim Ud Dwla. "Validation of theoritical approach to measure biodiversity using plant species data." Thesis, Högskolan i Skövde, Institutionen för biovetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-19431.
Abstract:
Measuring Biodiversity is an important phenomenon to serve best to our ecology and also keep environment sound. Variety of life on different levels, like an ecosystem, life forms on a site, landscape collectively known as Biodiversity. Species richness and evenness combine measures as Biodiversity. Separate formula, index, equation are widely using to measure Biodiversity in each level. Swedish Environmental Protection Agency aimed to establish an index that consists of landscape functionality and landscape heterogeneity. For landscape functionality assessment, there BBCI (Biotope biodiversity Capacity index) is going to use. High BBCI indicates a high biodiversity for each biotope. However, empirically estimate species richness how much matched with BBCI that not been evaluated. The aim of this paper to see the relationship between empirical estimated Biodiversity and BBCI. A relationship between Shannon diversity index and BBCI also ran to see the matches between them. Collect the empirical data from selected 15 landscapes using Artportalen.se and sort the data for further calculation. Results showed that there was a strong positive relationship between empirical estimated Biodiversity and BBCI. Again Shannon diversity index and BBCI also demonstrated a positive correlation between them. It showed BBCI could explain 60%-69% of species richness data and 17%-22% of Shannon diversity index. It indicates the acceptance of theoretical study of measure Biodiversity.
19
Imran, Hafiz Ali. "Remote Sensing Tools for Monitoring Grassland Plant Leaf Traits and Biodiversity." Doctoral thesis, Università degli studi di Trento, 2022. http://hdl.handle.net/11572/329592.
Abstract:
Grasslands are one of the most important ecosystems on Earth, covering approximately one-third of the Earth’s surface. Grassland biodiversity is important as many services provided by such ecosystems are crucial for the human economy and well-being. Given the importance of grasslands ecosystems, in recent years research has been carried out on the potential to monitor them with novel remote sensing techniques. Improved detectors technology and novel sensors providing fine-scale hyperspectral imagery have been enabling new methods to monitor plant traits (PTs) and biodiversity.
The aims of the work were to study different approaches to monitor key grassland PTs such as Leaf Area Index (LAI) and biodiversity-related traits. The thesis consists of 3 parts: 1) Evaluating the performance of remote sensing methods to estimate LAI in grassland ecosystems, 2) Estimating plant biodiversity by using the optical diversity approach in grassland ecosystems, and 3) Investigating the relationship between PTs variability with alpha and beta diversity for the applicability of the optical diversity approach in a subalpine grassland of the Italian Alps
To evaluate the performance of remote sensing methods to estimate LAI, temporal and spatial observations of hyperspectral reflectance and LAI were analyzed at a grassland site in Monte Bondone, Italy (IT-MBo). In 2018, ground temporal observations of hyperspectral reflectance and LAI were carried out at a grassland site in Neustift, Austria (AT-NEU). To estimate biodiversity, in 2018 and 2019 a floristics survey was conducted to determine species composition and hyperspectral data were acquired at two grassland sites: IT-MBo and University of Padova’s Experimental Farm, Legnaro, Padua, Italy (IT-PD) respectively. Furthermore, in 2018, biochemistry analysis of the biomass samples collected from the grassland site IT-MBo was carried out to determine the foliar biochemical PTs variability.
The results of the thesis demonstrated that the grassland spectral response across different spectral regions (Visible: VIS, red-edge: RE, Near-infrared: NIR) showed to be both site-specific and scale-dependent. In the first part of the thesis, the performance of spectral vegetation indices (SVIs) based on visible, red-edge (RE), and NIR bands alongside SVIs solely based or NIR-shoulder bands (wavelengths 750 - 900 nm) was evaluated. A strong correlation (R2 > 0.8) was observed between grassland LAI and both RE and NIR-shoulder SVIs on a temporal basis, but not on a spatial basis. Using the PROSAIL Radiative Transfer Model (RTM), it was demonstrated that grassland structural heterogeneity strongly affects the ability to retrieve LAI, with high uncertainties due to structural and biochemical PTs co-variation.
In the second part, the applicability of the spectral variability hypothesis (SVH) was questioned and highlighted the challenges to use high-resolution hyperspectral images to estimate biodiversity in complex grassland ecosystems. It was reported that the relationship between biodiversity (Shannon, Richness, Simpson, and Evenness) and optical diversity metrics (Coefficient of variation (CV) and Standard deviation (SD)) is not consistent across plant communities. The results of the second part suggested that biodiversity in terms of species richness could be estimated by optical diversity metrics with an R2 = 0.4 at the IT-PD site where the grassland plots were artificially established and are showing a lower structure and complexity from the natural grassland plant communities. On the other hand, in the natural ecosystems at IT-MBo, it was more difficult to estimate biodiversity indices, probably due to structural and biochemical PTs co-variation. The effects of canopy non-vegetative elements (flowers and dead material), shadow pixels, and overexposed pixels on the relationship between optical diversity metrics and biodiversity indices were highlighted.
In the third part, we examined the relationship between PTs variability (at both local and community scales, measured by standard deviation and by the Euclidean distances of the biochemical and biophysical PTs respectively) and taxonomic diversity (both α-diversity and β-diversity, measured by Shannon’s index and by Jaccard dissimilarity index of the species, families, and functional groups percent cover respectively) in Monte Bondone, Trentino province, Italy. The results of the study showed that the PTs variability metrics at alpha scale were not correlated with α-diversity. However, the results at the community scale (β-diversity) showed that some of the investigated biochemical and biophysical PTs variations metrics were associated with β-diversity. The SVH approach was also tested to estimate β-diversity and we found that spectral diversity calculated by spectral angular mapper (SAM) showed to be a better proxy of biodiversity in the same ecosystem where the spectral diversity failed to estimate alpha diversity, this leading to the conclusion that the link between functional and species diversity may be an indicator of the applicability of optical sampling methods to estimate biodiversity.
The findings of the thesis highlighted that grassland structural heterogeneity strongly affects the ability to retrieve both LAI and biodiversity, with high uncertainties due to structural and biochemical PTs co-variation at complex grassland ecosystems. In this context, the uncertainties of satellite-based products (e.g., LAI) in monitoring grassland canopies characterized by either spatially or temporally varying structure need to be carefully taken into account. The results of the study highlighted that the poor performance of optical diversity proxies in estimating biodiversity in structurally heterogeneous grasslands might be due to the complex relationships between functional diversity and biodiversity, rather than the impossibility to detect functional diversity with spectral proxies.
20
Rai, Upkar. "Characterisation of plant biodiversity in darjiling hills using remote sensing techniques." Thesis, University of North Bengal, 2006. http://hdl.handle.net/123456789/843.
21
Knapp, Sonja. "Plant biodiversity in urbanized areas analyses of plant functional traits in space and time, plant rarity and phylogenetic diversity." Wiesbaden Vieweg + Teubner, 2009. http://d-nb.info/995192685/04.
22
Achour, Rim. "Innovation végétale et propriété intellectuelle : approche dialectique du droit et de la science." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE3072.
Abstract:
Variété végétale et invention sont deux concepts juridiques qui encadrent la propriété intellectuelle des innovations variétales. Ces deux constructions juridiques sont en continuité avec les préceptes scientifiques de la biologie. En outre, elles sont adaptées aux besoins économiques des acteurs concernés. Ces deux éléments montrent que la relation entre le droit de la propriété intellectuelle et le contexte de la création variétale est construite sur un échange dialectique. Le choix du droit de la propriété intellectuelle dépend des intérêts que les sélectionneurs souhaitent fructifier. La coexistence des droits de la propriété est sujette aux stratégies d’appropriation mises en œuvre par les acteurs. Ces stratégies peuvent conduire à des limites : concentration des entreprises et perte de la biodiversité végétale. Ces limites sont étudiées au regard du droit de la concurrence d’une part, et au regard de la durabilité écologique, d’autre partPlant variety and invention are two legal concepts which regulate the intellectual property of varietal innovations. These two legal constructs are in line with the scientific precepts of biology. Moreover, they accommodate the economic needs of the actors involved. These two elements demonstrate that the relation between intellectual property law and the context of varietal creation is built on a dialectical interaction. The choice of intellectual property law depends on the benefits breeders wish to put forward. The coexistence of property rights is subject to the ownership strategies implemented by the actors. These strategies can show limitations: corporate concentration and loss of plant biodiversity. These limits are studied in terms of competition law and in terms of ecological sustainability
23
Brandt, Erika. "Relating Plant Spatial Pattern, Plant Biodiversity, and Ecosystem Function to Management Practices in Experimental Restored Wetlands." Oberlin College Honors Theses / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=oberlin1368092195.
24
Wilson, Frederick. "Factors affecting the species richness of old permanent semi-natural grasslands in North-East Scotland." Thesis, University of Aberdeen, 2003. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU173020.
Abstract:
The successful management for conservation and restoration of semi-natural ecosystems may be achieved only after the factors which regulate plant biodiversity and species composition have been identified. This study investigates the floristic composition and site characteristics of old permanent semi-natural grasslands in North-east Scotland and tests using pot and field experiments the role of soil fertility in determining vascular plant species richness, relative abundance and dynamics of communities. Results from field surveys show that, of the site characteristics quantified, vascular plant species richness is most strongly correlated (negative relationship) with extractable soil phosphorus. Where species richness is high (>40 in a study stand and >17 in a 1 m2 quadrat) extractable soil phosphorus levels (determined by ammonium acetate-acetic acid/polyacrylamide solution extraction and using inductively coupled radio frequency plasma spectrometry by the atomic emission method) are consistently very low (<1.9 mg 1-1 soil) by local agricultural standards. In pot experiments using soil from a site where high species richness is maintained, the loss of forb and graminoid species from synthesised communities may be shown to increase along a nutrient gradient created by incorporating increments of phosphorus. Despite a general increase in the above ground biomass of species which survive, those with the ability to form nitrogen-fixing nodules grow to dominate the community. By comparison, a nutrient gradient created by the incorporation of potassium has little effect on the species richness of synthesised communities. At field sites where the level of extractable soil phosphorus approaches that above which species-rich semi-natural grassland communities are not found to exist, the addition of nitrogen leads to species loss through the dominance of graminoid species. This effect may be intensified by applying phosphorus.
25
Fick, Hendrik Jacobus. "Managing biodiversity in a developing country mining context / Fick H.J." Thesis, North-West University, 2011. http://hdl.handle.net/10394/7337.
Abstract:
South Africa is one of the most biologically diverse countries in the world. However, biodiversity is suffering under the huge demand for natural resources and the increasing dependence of rural communities on these same resources. It has also become apparent that an alarming number of species are threatened, endangered or even destroyed. Surveys have revealed that 34% of the country’s 440 terrestrial ecosystems are threatened. The three severest threats to biodiversity are overexploitation, overgrazing and mining.
There is however a range of international, regional, national and local laws and best practice guidelines that aim to protect and preserve the natural faunal and floral diversity of the various rural areas and regions. The prescription of sustainable practices enables communities that depend on the services of ecosystem in their area, to utilise without depleting the resources provided by nature. South Africa is a signing party to more than seven conventions and treaties that either protect or govern biodiversity. In addition to this, the South African government has promulgated eighteen pieces of legislation and guidelines to protect and govern the use of biodiversity.
The focus of this study was on the impacts platinum mining have on biodiversity and how effectively these impacts are managed. Data for the case study was obtained from Impala Platinum. Impala leases its land from the Royal Bafokeng Nation and inter alia shares it with the people who use the areas in between for grazing and other subsistence activities.
The aim of the study was, in the first place to identify how Impala Platinum’s Environmental Management Plans (EMP’s) and Closure Plan (which manages current and post mining activities and their impacts) are aligned with the various international, national and local requirements for biodiversity management, and secondly to evaluate the effectiveness of the current management measures put in place, which regulates activities impacting on biodiversity.
To give effect to the above outcome it was necessary to first identify the various international, national and local treaties, legislature and guidelines. Secondly, an environmental risk assessment was conducted where the current management measure were weighed against the various international, national and local requirements in order to deduce the level of effectiveness of the current EMP’s and Closure plan. It was found that the majority of the EMP’s compiled under the Environmental Conservation Act No. 73 of 1989 (ECA) lack substantive management and preventative measures. It was only in the later EMP’s (between the years 2000 - 2004) that the prescribed management measures improved and became more effective. This was because the Environmental Impact
Assessment (EIA) process had matured in South Africa and an entire new regime of more descriptive EIA regulations had been promulgated under the National Environmental Act No. 107 of 1998, which repealed the majority of the outdated ECA regulations.
It was also found that the environmental standards, management objectives and priorities that were developed in the EMP’s did not contingently and specifically reflect the conditions in relation to the environmental, developmental and biodiversity contexts to which they apply. The Closure plan on the other hand, was a regurgitation of the same unimaginative objectives focusing on remedying past legacies instead of providing a lasting solution to sustain and improve the environmental conditions left by the mine, and most importantly it does not address the social issues that result from mine closure. For example, the overexploitation and overgrazing of the areas in between the various mining operations by the Royal Bafokeng Nation’s people is a crucial aspect that has not been thoroughly addressed in the respective documents. Habitat disturbance, which was not addressed for instance, requires a wide range of actions e.g. educating local communities on pasture management, post–rehabilitation monitoring, amelioration etc.
To improve compliance with current legislation and adherence to the guidelines proposed by best practice initiatives, various recommendations are put forward to control both the negative activities brought on by the Royal Bafokeng and Impala Platinum. These include the implementation of: Biodiversity (inclusive) impact assessment, good environmental governance, the precautionary approach, the ecosystems approach, sustainable biodiversity management practices through conservation planning, biodiversity action plans, stewardship and land care tools, conservation plans, biodiversity offsets, effective mine closure planning and the forming of a Biodiversity Action Steering Committee (BASC).
Finally, an eight step model is proposed as a tool to evaluate the effectiveness of specifically the platinum mine’s EMP’s and Closure plans to manage activities affecting biodiversity. The model is based on the concepts of direct and indirect drivers of change and the Deming cycle and is an elaboration of the model proposed by UNEP and the International Association of Impact Assessment. The model focuses on both the natural and anthropogenic drivers that may affect biodiversity and will aid the management of a mine to supplement the shortcomings of these documents. As an indirect outcome the model may possibly even improve, the relationship between the specific company and the communities with which it shares its land.Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2012.
26
Davie, Kim. "The biodiversity and epidemiology of potato virus Y (PVY) in Scotland." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/27766/.
Abstract:
Potato virus Y (PVY) is considered to be the most serious viral pathogen that affects potato crops worldwide and can cause substantial yield losses. PVY exists as a complex of strains that can be distinguished on the basis of their biology, serology and genome analysis. In recent decades novel recombinant PVYN strains have emerged that can cause Potato Tuber Necrotic Ringspot Disease (PTNRD). It is therefore important to understand the potential threat to the Scottish seed potato industry. This molecular nature of PVY isolates in Scotland was established through the use of partial sequencing, revealing a predominance of isolates belonging to the molecular EU-NTN clade (ca 75%). Assessing the biological characteristics of selected isolates indicated that most isolates in Scotland belong to the biological PVYN type, however PVYE is also present. Molecular analysis of a PVYE isolate has shown that identifying the molecular determinants for vein necrosis production in tobacco is complex. Although it has not been reported from the field in Scotland, PTNRD initiation is possible with most PVYN isolates under optimal climatic conditions. Field trials suggest that PVYEU-NTN is more efficiently transmitted by aphids across a growing season than PVYNA-NTN and PVYO, with a higher than expected proportion of tubers infected with the PVYEU-NTN isolate. This suggests that once plants are inoculated with the virus, PVYEU-NTN isolates are more likely to infect progeny tubers. Taken together, the outcomes of this project should provide a better understanding as of PVY molecular nature in Scotland its pathogenicity and epidemiology with the view to understanding why PVYN variants have become an important threat for the seed potato industry both in Scotland and worldwide.
27
Bigirimana, Joseph. "Urban plant diversity patterns, processes and conservation value in Sub-Saharan Africa: case of Bujumbura in Burundi." Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209636.
Abstract:
This study focuses on the vegetation of the African city of Bujumbura, Burundi. Urban flora is detailed according to the origin of the species (native or introduced), their life form, the use of these species by the local population and their behaviour (invasive or not). The correlation between different natural and anthropogenic environmental factors and the composition of plant communities has been demonstrated through the analysis of vegetation plots. Three types of green areas were studied: spontaneous vegetation on terra firma, wetlands
and domestic gardens.
The main ecological factor correlated to the composition of the spontaneous vegetation of terra firma is the degree of urbanization. From the suburb to the city centre, savannah species typical for the region are replaced by alien invasive species, mostly ruderals. The latter generally have a large distribution, often on several continents. The physiognomy of the vegetation also changes, with hemicryptophytes and phanerophytes in the outskirts and the dominance of therophytes and chamaephytes in the city centre.
In most of wetlands, a large proportion of the plant species are natives, but some wetlands are almost totally invaded by alien species. Soil type is the main environmental factor correlated with
the variability of the vegetation.
The flora of domestic gardens is mainly composed of introduced species used as ornamental, food or medicinal plants. The socio-economical status of the neighbourhood is the main factor correlated with the variability of the garden flora. In high standing neighbourhoods, most species are onamental, with many trees and shrubs. In popular neighbourhoods, the flora is mainly utilitarian (vegetables and fruits), with a significant proportion of native species, and composed mainly of annual species.
A small proportion of the alien species cultivated in gardens has become invasive in the semi-natural vegetation of the city and its surroundings. Many other species cultivated in the gardens could become invasive, based on their ecology and their invasive behaviour in other regions with a climate similar to that of Bujumbura.
Overall, the city of Bujumbura has a diverse flora, with many useful species (vegetables and fruits, traditional medicine, construction of fences and roofs, material for mats and art objects.). The vegetation also hosts wildlife: birds, fishes, hippos, crocodiles etc…
In conclusion, the vegetation of Bujumbura contributes to biodiversity conservation and provides services to the urban population, but the expansion of alien invasive species and the consequent homogenization of the vegetation is a challenge for the future.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
28
Martinez, Araneda Camila. "Plant phylogeography in southern South America." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/5041.
Abstract:
This thesis is a phylogeographic investigation into plant species from Patagonia, and aims to infer their past distributions from the study of genealogical lineages. These species have gone through several events such as glacial periods, volcanism and topographical change which are expected to contribute to the divergence of genetic lineages by shaping distributions, isolating populations and therefore changing their genetic structure. So understanding how these processes have affected populations is important to get information on how the biodiversity in the region has been assembled, to identify hotspots of intra-specific diversity and therefore to establish potential conservation priorities. Several multi-species phylogeographic studies have been done in the northern hemisphere, but only few are published for South America and even less for the studied area. Patagonia is an area of a great interest because is the only area in the southern hemisphere apart from Antarctica that have been covered buy a thick layer of ice within the glacial periods. It has high levels of endemism, due to its natural boundaries and environmental processes, and is a biodiversity hotspot for conservation. Its varied topography (two big mountain ranges with a north-south distribution divided by a low flat area) also makes Patagonia interesting to study, due to the likelihood of this impacting on phylogeographic patterns. This study encompass seven different Patagonian species of which one is a range restricted conifer and the rest are all angiosperms and include trees, shrubs and herbs with a broad distributions. The reason why I have chosen so many different species is to look for general phylogeographic patterns in species in this region. The thesis was constructed in five chapters. The first is an introductory chapter that provides background to the study system and concepts. Chapters 2, 3, and 4 are empirical phylogeographic studies. These are written as self-contained chapters with the intention that each will be submitted as a separate paper. This leads to some repetition between chapters, but this is intentional as each will need to ‘stand alone’ when submitted for publication. Chapter 2 is a general investigation into five different Patagonian plant species: Discaria chacaye, Donatia fascicularis, Escallonia virgata, Tepualia stipularis and Weinmannia trichosperma. Chapter 3 describes the phylogeographic structure of Gentianella magellanica an annual, cold tolerant species with a wide distribution throughout Patagonia. This species was treated separately and in more detail than the previous five species due to its marked phylogeographic structure. Chapter 4 describes the phylogeographic structure of a Chilean endemic conifer Prumnopitys andina. This has a small distribution in the Andes and only one known population in the coastal cordillera. It was treated separately due to its restricted distribution and different mode of chloroplast inheritance (paternal). Chapter 5, is a general summary, bring all of the results together and giving a wider explanation of the phylogeographic patterns for all species and an outline of future research areas.
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Fabricius, Christo 1956. "The impact of land use on biodiversity in xeric succulent thicket, South Africa." Doctoral thesis, University of Cape Town, 1997. http://hdl.handle.net/11427/9512.
Abstract:
Bibliography: leaves 100-114.Human-induced land management practices are key factors which influence the dynamics of landscapes, land elements and biotic communities in Xeric Succulent Thicket, a notoriously fragile and low resilience ecosystem in the Eastern Cape, South Africa. In its natural state this vegetation type is characterized by a continuous mosaic of clumps of diverse woody shrubs in a matrix of grass, hardy dwarf shrubs and bare ground. When indigenous herbivores are replaced by domestic livestock at unsustainable stocking rates, the ratio of clump to interclump areas decreases. This has impacts on biodiversity at the landscape level, and affects the composition and species richness of plant, arthropod and reptile communities and fungal symbionts. The study has two main objectives: 1) to detennine the local-level effects of different types of land use on biodiversity in Xeric Succulent Thicket; and 2) to better understand the factors which affect biodiversity in different taxonomic groups and at different spatial scales, so that the preservation function of protected areas could be enhanced. The key questions which are addressed in the thesis are what does 'biodiversity' mean, and what are its different dimensions in Xeric Succulent Thicket; what roles do protected areas and other lands play in preserving biodiversity, how are different taxonomic groups affected by different types of land use; and how can biodiversity be monitored and measured? . The regional 'conservation landscape' is seen as the protected area plus the land immediately adjoining it, and is viewed as an integrated mosaic of anthropogenic landscapes (land management units), land elements (patches within landscapes). producer communities (assemblages of interacting plant species), consumer communities (assemblages of interacting herbivores and predators) and soil microorganisms. From a process point of view, the research relates the intensity of disturbance, mainly as a result of herbivory, to landscape complexity, the structure of land elements, and the species richness of producers and consumers within land elements. The patterns which emerge are interpreted in the context of ecosystem functioning, from the point of view of a practicing conservation biologist.
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CAVALLORO, VALERIA. "Exploiting the Pavia territory plant biodiversity for the discovery of proteasome modulators." Doctoral thesis, Università degli studi di Pavia, 2022. http://hdl.handle.net/11571/1449465.
31
Maguire, Victoria. "Immunogold labelling of TIP proteins in the resurrection plant Craterostigma plantagineum." Thesis, University of Cape Town, 2000. http://hdl.handle.net/11427/26509.
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Louw, Merika. "Propagation and stress physiology of selected Subtropical Thicket species : towards increasing biodiversity at rehabilitation sites." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1021115.
Abstract:
Sundays Thicket and Spekboomveld vegetation in the Eastern Cape have experienced intensive and extensive degradation due to over-browsing by domestic stock. The Subtropical Thicket Restoration Project aims to take advantage of the high carbon sequestration potential of Portulacaria afra (Spekboom) and other Thicket species, to rehabilitate degraded Thicket by restoring biodiversity and ecosystem services, create job opportunities and socio-economic upliftment in local communities, and promote the trade of carbon credits generated by planting and „farming‟ with Spekboom truncheons, rather than domestic stock. Plant material (seeds and length of stem) was sourced from the farm Krompoort, outside Uitenhage in the Eastern Cape. The effectiveness of four different rooting media i.e. plain pool filter sand and 1:1 mixtures of pool filter sand with perlite, potting soil and Thicket soil, on the rooting of ten Thicket species, were tested. Species with the greatest percentage strike and mean root length on stem cuttings were succulent species, Crassula ovata (84 percent strike) and Portulacaria afra (97 percent), as was expected. The application of rooting hormone Seradix© No. 3 did not significantly promote cutting strike or increase mean root length in C. ovata and P. afra. Woody canopy shrub species with the greatest cutting strike and mean root length, overall, were Rhigozum obovatum (24 percent), Lycium cinereum and L. oxycarpum (21 percent), and Searsia longispina (19 percent). These species, as well as Grewia robusta (4 percent), are considered „easy-to-root‟ species, or of sufficient functional value in terms of their spinescence, flower and fruit production, and soil-binding capabilities. Very low percentage strike (<1 percent) and mean root length were achieved in Azima tetracantha, Carissa bispinosa and Gymnosporia polyacantha subsp. polyacantha. These species are considered unsuitable for propagation for rehabilitation purposes. Crassula ovata, L. cinereum, L. oxycarpum, P. afra and S. longispina cuttings produced longer roots when planted in Thicket soil, the same having been found in R. obovatum cuttings planted in perlite. Thicket soil was, therefore, best at promoting cutting strike and root growth in „easy-to-root‟ species. Plain pool filter sand was the only medium in which A. tetracantha, C. bispinosa and G. robusta, cuttings rooted, and perlite the only medium in which G. polyacantha subsp. polyacantha cuttings rooted. Potting soil did not promote significant cutting strike or root growth in any of the species tested. Physiological variables i.e. photosynthetic efficiency (chlorophyll a fluorescence, Fv/Fm) and stomatal conductance (mmol H2O m-2 s-1) were measured for ten Thicket species, including Portulacaria afra. Control plants were watered well once a week, and treatment plants were dried out for 30 days, rewatered on the 30th day and their recovery from drought stress monitored for a further 17 days. Species that responded poorly to drought stress were Gymnosporia buxifolia and Putterlickia pyracantha. In addition to Portulacaria afra, species that showed the fastest recovery and resprout after rewatering, were: Crassula ovata, Ehretia rigida, Grewia robusta, Lycium ferocissimum, Rhigozum obovatum and Searsia longispina. These species produced the smallest decline in volumetric moisture content of soil, and had the lowest decline in photosynthetic efficiency and stomatal conductance during simulated drought. Unlike C. ovata and P. afra, which are CAM or C3-CAM switching species, mortality of transplants will most likely be high, if not total, during transplantation, as this study was done at lower light and temperature, and higher humidity levels than experienced at rehabilitation sites. This study has shown that the reintroduction of propagated woody canopy shrubs and trees into degraded Thicket sites does not appear to be a practical or economical method of actively restoring biodiversity to rehabilitation sites. As woody climax species have been shown to return to sites planted with Spekboom truncheons through „natural regeneration‟ within approximately 50 years, future research efforts should focus on optimising restoration site selection and planting techniques in order to maximize carbon sequestration potential of planted truncheons, which will, in the long term, result in an environment that can support regeneration of the biodiversity to something resembling intact Thicket.
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Miloud, Youssra. "Etude du potentiel bénéfique des souches de Rhizobium pour Medicago truncatula : symbiose, solubilisation du phosphate et lutte contre la verticilliose." Thesis, Toulouse, INPT, 2018. http://www.theses.fr/2018INPT0123/document.
Abstract:
En raison de leur capacité à former une symbiose avec des bactéries du sol appelées Rhizobium, ces bactéries fixent l’azote atmosphérique et leurs plantes-hôtes n’ont donc pas besoin de fertilisant azoté, les légumineuses jouent un rôle important dans l'agriculture. En outre, certaines souches de Rhizobium ont la capacité de solubiliser le phosphate, fournissant ainsi du phosphore assimilable aux plantes hôtes. Une aptitude à lutter contre certains agents pathogènes a aussi été démontrée dans plusieurs études. La présente étude évalue l’efficacité symbiotique de rhizobiums tunisiens, leur capacité à solubiliser le phosphate, et leur aptitude à lutter contre la verticilliose ainsi que d’autres champignons pathogènes chez Medicago truncatula. Trente-six isolats de rhizobiums prélevés sur des nodules racinaires de M. truncatula provenant de différentes régions de Tunisie ont été obtenus pour ce travail. Environ 60% de ces isolats étaient capables de solubiliser le phosphate in vitro. Dans une seconde étape, trois rhizobiums solubilisant le phosphate et un isolat incapable de solubiliser le phosphate in vitro ont été utilisés pour des essais en phytotron afin de voir l’effet de la présence des rhizobiums sur les paramètres de croissance des plantes en présence de phosphate inorganique sous forme de CaHPO4 et rocheux sous forme brute. Les résultats de l’essai montrent que les plantes de la lignée A17 traitées au CaHPO4, ont tendance à produire plus de nodules et de biomasse aérienne que la lignée F83005.5 et que la forme du phosphate utilisé, soluble ou non soluble, affecte les paramètres étudiés. L'inoculation de quatre lignées de M. truncatula avec 16 isolats de rhizobium sélectionnés auparavant a montré une interaction significative entre les isolats et les lignées pour la symbiose visible par la formation de nodules. Tous les isolats de rhizobium testés ont augmenté la biomasse aérienne des plantes, réduit la biomasse racinaire et entraîné une teneur plus élevée en azote mais l’effet dépendait de l’isolat de rhizobium et de la lignée de M. truncatula utilisés. Enfin, ces isolats ont été testés pour leur capacité à protéger des plantes de M. truncatula contre une maladie racinaire, la verticilliose. Des activités antagonistes in vitro contre divers champignons pathogènes dont Verticillium et Fusarium ont également été recherchées permettant d’identifier un isolat efficace pour la lutte biologique. Les résultats de cette étude suggèrent que des isolats de rhizobium sélectionnés pourraient être utilisés comme biofertilisants dans les sols pauvres pour réduire l'utilisation d'engrais chimiques azotés et phosphorés mais pas pour lutter contre la verticillioseBecause of their ability to form a symbiosis with soil bacteria called Rhizobium, legumes play an important role in agriculture. These bacteria fix atmospheric nitrogen; hence their host plants do not need nitrogen fertilizers. In addition, some strains of Rhizobium have the ability to solubilize phosphate, thus providing phosphorus to host plants. An ability to control certain pathogens has also been demonstrated in several studies. The present study evaluates the symbiotic efficiency of Tunisian rhizobia, their ability to solubilize phosphate, and their ability to control Verticillium wilt and other pathogenic fungi in Medicago truncatula. Thirty-six rhizobial isolates were obtained from root nodules of M. truncatula from different parts of Tunisia were used in this work. About 60% of these isolates were able to solubilize phosphate in vitro. In a second step, three phosphate solubilizing rhizobia and one isolate unable to solubilize phosphate in vitro were used for phytotron assays to see the effect of the presence of rhizobia on plant growth parameters in the presence of soluble and insoluble forms of phosphate. The results of the experiment show that A17 plants treated with CaHPO4, tend to produce more nodules and shoot biomass than F83005.5 and that the phosphate form used, soluble or non-soluble, affects parameters studied. Inoculation of four M. truncatula lines with 16 previously selected rhizobial isolates showed significant interaction between isolates and lines for symbiotic abilities as visualised by nodule formation. All rhizobial isolates tested increased above-ground biomass, reduced root biomass, and increased nitrogen content with strains effects of plant genotype and bacterial isolate. Finallly, these isolates were tested for their ability to protect M. truncatula plants against Verticillium wilt, and to inhibit the growth of pathogenic fungi such as Verticillium and Fusarium in vitro. However, no isolate could be identified as effective for biological control. The results of this study suggest that selected rhizobial isolates could be used as biofertilizers in poor soils to reduce the use of nitrogen and phosphorus fertilizers but not to control Verticillium wilt
34
Rowe, Rebecca L. "Implications for biodiversity of the deployment of commercial scale short rotation willow coppice." Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/195559/.
Abstract:
Willow short rotation coppice (SRC) is seen as an important renewable energy source within temperate regions including the UK and its deployment within the agri-environment is supported by a number of goverment policies. Willow SRC represents a significant land use change and its deployment has raised questions regarding the possible impacts on biodiversity and the delivery of ecosystem services. This work assessed the impact of three commercial willow SRC plantations on ecosystem processes through the use of herbivory, decomposition and predation bioassays. Comparisons were also made between the willow SRC plantations and the abundance and diversity of: summer ground flora and winged invertebrates in the alternative land use options of set-aside and cereal crops; predatory ground invertebrates and small mammals in winter wheat and barely. In comparison to cereal crops the willow SRC plantations contained a higher abundance and species richness of ground flora and small mammals, and a higher abundance and family richness of predatory ground invertebrates. Ground flora richness was higher in the set-aside land than within the willow SRC. The ground flora community within the willow SRC was markedly different to both set aside and arable land with a shift from an annual and ruderal to competitive and perennial dominated community. The composition of winged invertebrate Orders also varied between the land uses with higher numbers of Hymenoptera and Hemiptera trapped within the willow SRC plantations than within the arable and set-aside land. No differences were detected on rates of predation on invertebrate prey, seedling herbivory and decomposition between willow SRC and set-aside land. In comparison to cereal crops higher rates of decomposition and higher rates of predation by small mammals in the autumn were recorded in willow SRC. Overall the results suggest that, willow SRC plantations may benefit farm-scale biodiversity by providing a habitat where plants and animals that are uncommon on alternative land use can persist. Moreover positive effects on the species richness of small mammals and the abundance and richness of predatory invertebrates may have positive implication for natural pest control both within willow SRC plantations and possibly on surrounding landscape. Comparisons to set-aside did, however, highlight that willow SRC is not a panacea for all species and care must be taken in the location and fraction of the landscape that is devoted to this crop
35
Maholland, Peter D. "Effects of Prescribed Fire on Upland Plant Biodiversity and Abundance in Northeast Florida." UNF Digital Commons, 2015. http://digitalcommons.unf.edu/etd/562.
Abstract:
Terrestrial ecosystems in the southeastern United States have evolved with fire as a common disturbance and as a result many natural communities require the presence of fire to persist over time. Human development precludes natural fires from occurring within these communities; however, prescribed fire is considered to be a critical tool in the effort to restore fire-dependent ecosystems after decades of fire exclusion. Direct effects of fire on individual floral and faunal species as well as benefits to biodiversity at the landscape (gamma diversity) level have largely been supported in previous research. However, information on the effects of natural and prescribed fire on plant diversity at the local level (alpha diversity) is limited, particularly for southeastern forests. The applicability of the Intermediate Disturbance Hypothesis (IDH), which suggests that the highest levels of biodiversity are found at intermediate levels of disturbance, is also untested for North Florida upland plant communities. This study compared the effects of fire on local scale mean plant species diversity by examining burned and unburned portions of three fire-dependent communities to determine if there is an effect of prescribed fire on in alpha biodiversity. Alpha biodiversity was not significantly different (p=0.433) between burned and unburned fire-dependent plant communities in northern Florida, suggesting that prescribed fire does not affect plant species diversity in these communities and/or the IDH for plant communities is not supported at the time scale tested. However, the application of prescribed fire did result in changes in abundance of species, particularly with species such as Dicanthelium acuminatum, Quercus myrtifolia, and Vaccinium myrsinites, that respond positively to fire, which may have implications for associated faunal diversity.
36
Ferreira, Mariana Moreira. "Biodiversity and plant-pollinator interactions in native forest areas of Terceira Island (Azores)." Master's thesis, Universidade de Évora, 2018. http://hdl.handle.net/10174/23061.
Abstract:
Neste trabalho avaliámos o impacto que a perturbação humana das comunidades da floresta nativa da ilha Terceira (Açores) tem sobre a riqueza específica e nas interações ecológicas entre plantas e polinizadores. Para o efeito selecionámos dois locais emparelhados (um bem conservado e outro degradado), em duas áreas de estudo (Lomba e Pico Galhardo) e analisámos a integridade das redes ecológicas planta-polinizador. Constatámos que nas áreas bem conservadas as interações são dominadas por espécies nativas, enquanto que nas áreas perturbadas, apesar da prevalência de plantas introduzidas, os polinizadores nativos têm um papel relevante. Em cada área houve apenas uma planta que concentrou as visitas dos polinizadores, que na sua maioria pertenceram à ordem Diptera e tiveram hábitos generalistas; Biodiversity and plant-pollinator interactions in native forest areas of Terceira island (Azores)
Abstract: In this work we evaluate the effect of anthropogenic disturbance in native forest communities of Terceira island (Azores) on species richness and on plant-pollinator ecological interactions. We selected paired sampling sites (one well-preserved and one disturbed) in two study areas (Lomba and Pico Galhardo) and we analysed plant-pollinator networks integrity. We found that native species dominate in well-preserved sites whereas in disturbed sites, despite the prevalence of introduced plants, native pollinators play an important role. In each area there was a plant that received most of the insect visits, being these mainly from Diptera order and having generalist behaviour.
37
Reimark, Josefin. "How has time and space affected plant biodiversity in the Hjälmö-Lådna archipelago?" Licentiate thesis, Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-79230.
Abstract:
Traditionally European farmland management has declined during the last century, mainlydue to abandonment or intensification. When traditional management is replaced by newmethods many species are negatively affected and often threatened with extinction. In thisthesis, the Stockholm archipelago is used as a platform to study the effects of land use changeover time. The overall aim is to examine how time and space affects plant biodiversity in arural landscape, with focus on heterogeneous pastures. Historical records and maps were interpreted together with aerial photos and used to constructfour time-layers of land use: reflecting the landscape 200 years ago, 100 years ago, 50 yearsago and present. Investigations of plant species richness was conducted in seven habitats; 1)grazed fields, 2) grazed forest edges, 3) grazed forest interior, 4) former grazed fields, 5)former grazed forest edges, 6) former grazed forest interior, and 7) historical pasture islands,on 35 islands in Hjälmö-Lådna archipelago on the east-coast of Sweden. Plant speciesrichness was measured for all plant species and for grassland specialist species at three scales:i) fine-scale diversity (α div), ii) large-scale diversity (γ div ), and iii) spatial turnover (β div).Using Structural Equation Models (SEM) the variation in species diversity and plantcommunity composition was investigated in relation to landscape context, space andmanagement history. The land use change in the Hjälmö-Lådna archipelago followed the general trends on themainland in Sweden and the rest of Europe with loss of traditional managed habitats, such asmeadows or wooded pastures. However, no intensification and large-scale agriculture hasdeveloped on the islands, mainly because of physical limitations, but also because ofeconomical and conservation reasons. Surprisingly, the grazing pressure on the remaininggrazed habitats had not changed notable over the last century; although the study area was notparticularly species rich (highest average was 15 species/ m2 in grazed fields). Adjacenthabitats; field and wood pasture, showed a higher similarity in community composition thanexpected compared to random pairs. Grazing and proportion of openness had a positiveinfluence on species richness and especially on grassland specialists. The variation of totaldiversity at the landscape scale was best explained by the heterogeneity of grazed forest edgesand the local species diversity in fields. The results from the study suggest that grazing is important also in species-poor landscapes,and that it can aid in protecting and promote species-richness also in other types of speciespoorlandscapes. To prevent further loss of biodiversity it is necessary to keep fields andforest edges open with continuous management. To maintain values of high biodiversity andculture in the archipelago it is therefore important that farmers are subsidised by EU tocontinue to grazie heterogeneous habitats and pastures with many trees.
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Pornaro, Cristina. "Effects of wood establishment on plant biodiversity and herbage production of mountain pastures." Doctoral thesis, Università degli studi di Padova, 2012. http://hdl.handle.net/11577/3422525.
Abstract:
In the past sixty years, the Southern Alps have undergone a tremendous and likely unprecedented change in land-use due to land abandonment in mountain regions. This phenomenon causes a turn of mountain grasslands to forests through the process of natural succession.
Vegetation relevés in eight pastures under forest succession in the Italian Alps were collected at different percentage of wood cover. Moreover, in four of the eight sites, herbage samples were collected at different wood cover levels. In addition, in one site (characterised by Nardus grassland habitat) core samples were collected in order to study root characteristics. Species richness, botanical composition, dry matter production and contents, and root characteristics were taken into account in order to analyze the effect of wood cover on plant diversity, herbage yield and quality, and soil stability.
The effect on specie richness due to this process is different among sites because of differences in environmental factors and human activities. In general species richness decreased with increasing wood cover, and the reduction was more relevant in sites at low altitude. In some sites the effect of reforestation on plant species richness showed a slight increase at low percentage of wood cover followed by a gradual decrease, while in the others the effect displayed a monotonic decrease. Modelling with a generalized linear mixed model suggested that mean annual temperature was the primary determinant of the functional relationship. Differences among sites were not found when botanical composition, and in particular Bray dissimilarity index, was taken into account.
A reduction of dry matter yield was noted in most of the studied sites. Forest succession affected herbage quality decreasing it starting from low percentage of wood cover because of changes in crude protein and fibrous contents.
When root characteristics were analyzed, root length density and average diameter declined at 75% of wood cover increasing the risk of soil erosion.
Based on this results, mountain areas with low relevance for dairy production grazing should be encouraged for preserving both biodiversity and the stability of habitat. The strong effect of temperature on the loss of species richness suggests that the risk increases with lower altitude and stronger exposition towards South. The maintenance of low percentage of wood cover is useful for the habitat ecological value. On the contrary, in mountain areas where dairy production grazing is relevant, the management should be assessed for excluding wood establishment on the grazing surface.Negli ultimi sessant’anni, nell’ambiente alpino ed in particolare nelle Alpi italiane, si è assistito ad un importante e senza precedenti cambiamento d’uso del suolo, dovuto all’abbandono delle zone montane. Questo fenomeno ha causato un avanzamento del bosco su prati e pascoli attraverso un processo naturale di riforestazione. Per questo studio sono stati eseguiti rilievi floristici in otto pascoli montani delle Alpi italiane, soggetti ad avanzamento del bosco. Inoltre, in quattro di questi otto siti sono stati raccolti campioni di foraggio per la determinazione della produttività e della qualità della fitomassa. Infine, in un sito, caratterizzato dalla presenza di habitat a Nardus stricta, sono state raccolte carote di terreno per la caratterizzazione della componente ipogea. In tutti i casi i rilievi e i campionamenti sono stati eseguiti a percentuali crescenti di copertura arboreo-arbustiva. Sono stati considerati i seguenti parametri: numero di specie, composizione botanica, produzione e composizione chimica della sostanza secca nonché densità e diametro medio della radici a diversi livelli di profondità nel terreno, in modo da analizzare l’effetto della copertura arboreo-arbustiva su diversità vegetazionale, produzione e qualità del pascolo e stabilità del suolo. L’effetto sul numero di specie causato dall’avanzamento del bosco è risultato diverso tra i siti a causa delle differenze che intercorrono nei fattori ambientali e nelle attività antropiche. In generale si è assistito ad una diminuzione del numero di specie per effetto dell’avanzamento del bosco, in alcuni siti però è stato osservato un leggero aumento per bassi valori di copertura arboreo-arbustiva. La diminuzione del numero di specie è stata più marcata nei siti ad altitudine inferiore. Usando un modello lineare misto generalizzato, è stato riscontrato che le temperature medie annue sono uno dei fattori che meglio spiegano la diversa relazione tra i siti. L’analisi della composizione floristica mediante l’indice di Bray, ha evidenziato un comportamento simile tra i siti. Nella maggior parte dei siti analizzati si è riscontrata una diminuzione della produzione in sostanza secca per effetto della copertura arborea. Inoltre, già a partire da basse percentuali di copertura arboreo-arbustiva, è stata osservata una diminuzione della qualità della fitomassa prodotta dal pascolo, per effetto di una diminuzione del contenuto di proteina grezza ed un aumento delle fibre. Relativamente alle radici, si è osservato come la densità radicale in lunghezza e il diametro medio diminuissero drasticamente a percentuali di copertura arboreo-arbustiva del 75%, aumentando verosimilmente il rischio di erosione del suolo. Sulla base di questi risultati possiamo dire che nelle regioni montane, laddove la vocazione produttiva (in termini di produzione casearia) è poco rilevante, andrebbe incoraggiato il mantenimento di questi habitat a vantaggio della biodiversità e della stabilità del suolo. Come visto in questo studio, l’effetto della temperatura media annua sulla diminuzione del numero di specie, suggerisce che il rischio di perdita di biodiversità aumenta ad altitudine minore e in aree esposte a sud. Il mantenimento di basse percentuali di alberi o arbusti può essere utile per conservare il valore naturalistico di questo habitat. Al contrario, nelle zone dove la vocazione casearia del pascolo è prevalente, la gestione dovrebbe essere tale da mantenere le superfici a pascolo completamente libere da alberi e arbusti.
39
Patrick, L. Brian. "Fertilization and plant litter effects on the plant and epigeal arthropod communities." [Kent, Ohio] : Kent State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=kent1259588844.
Abstract:
Thesis (Ph.D.)--Kent State University, 2009.Title from PDF t.p. (viewed April 14, 2010). Advisor: Mark W. Kershner. Keywords: biodiversity; nitrogen; fertilization; plant litter; trophic dynamics; epigeal community. Includes bibliographical references.
40
Steffan, Shawn Alan. "Biodiversity and fear ecology the cascading effects of species richness and nontrophic interactions /." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Dissertations/Spring2009/s_steffan_041709.pdf.
41
Kjellström, Felicia. "Impact of Olive Cultivation on Biodiversity in Messenia, Greece." Thesis, Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-107144.
Abstract:
The biggest threat and cause to loss of biodiversity have been found to be the intensification of agriculture under the 20th century. Messenia is one of the oldest olive cultivation areas in Greece and the landscape is dominated by olive groves characterized by extensive tillage, which causes serious erosion and might be a threat to plant diversity. Organic olive cultivation is an alternative that aims to preserve and support biodiversity. In this study the plant composition in the edge zones of an organic and a conventional olive grove in Messenia were inventoried to be able to investigate if organic cultivation methods enhance plant diversity. Moreover, other factors affecting plant diversity in olive groves and suggestions for precautions in the olive cultivation sector to support biodiversity are discussed. The results show that the organic olive grove hosted 40 % higher species richness, which indicates, as in other similar studies, that the organic olive cultivation methods have a higher capacity to support biodiversity. By restricting tillage and promoting organic olive cultivation, not only biodiversity would be enhanced; this could also prevent further soil erosion and create a more heterogenic agricultural landscape with higher biological and cultural values.
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Marshall, Carolyn Bowers. "Effect of plant functional group removal on the soil microbial community diversity and composition." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/2865.
Abstract:
A major objective of biodiversity-ecosystem functioning (BDEF) research is to determine the consequences of species loss, caused both naturally and anthropogenically, on the functioning of ecosystems. The impact of plant species loss on the soil microbial community has not received much attention even though soil microbes influence many important ecosystem functions such as decomposition and nutrient cycling. The objective of this research was to investigate how the functional group composition of the aboveground plant community influenced the belowground microbial community. Plant functional groups (graminoids, legumes and non-leguminous forbs) were removed from a northern grassland system in the Yukon Territory, Canada. One metre square plots had one of the three functional groups removed or left intact as a control and this was crossed with a fertilizer treatment and a fungicide treatment that targeted mycorrhizal fungi. After five seasons (2003-07) of implementing treatments the soil microbial community was analyzed using substrate-induced respiration (SIR, a measure of metabolic diversity) and phospholipid fatty acid analysis (PLFA, a measure of community composition). Plant functional group removal had almost no effect on the soil microbial community. The only response detected was an increase in stress (indicated by the PLFA stress ratio of cy19:0 to 18:1ω7c) which occurred when legumes were removed and fertilizer was not added, indicating that legumes had a positive effect on the nutrient status of microbes. Likewise, soil properties (total carbon, pH, moisture and nutrients) showed limited response to plant removals. Fertilization decreased the metabolic diversity of the soil microbial community. We detected no soil microbial or plant biomass response to the fungicide indicating that mycorrhizae had little influence in this system. Based on the low-productivity of the grassland, and the lack of response in both the soil properties and the microbial community, we hypothesize that the main determinants of the microbial community may be litter input. When litter decomposition rates are slow, such as in this northern system, five growing seasons may not be sufficient to detect the impact of a changing plant community on the soil microbes.
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Peyre, Gwendolyn. "Plant diversity and vegetation of the Andean Páramo." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/296441.
Abstract:
The páramo is a high mountain ecosystem that includes the natural and semi-natural habitats located between the montane treeline and the permanent snowline in the humid Northern Andes. Given its recent origin and continental insularity among tropical lowlands, the páramo evolved as a biodiversity hotspot, with a vascular flora of more than 3400 species and high endemism. Moreover, the páramo provides many ecosystem services for human populations, essentially water supply and carbon storage. Anthropogenic activities, mostly agriculture and pasture practices, as well as climate change are major threats for the páramo’s ecological integrity. Consequently, further scientific research and conservation strategies must be oriented towards this unique region. Botanical and ecological knowledge on the páramo is extensive but heterogeneous. Moreover, most research studies and management strategies are carried out at local to national scale and given the vast extension of the páramo, regional studies are also needed. The principal limitation for regional páramo studies is the lack of a substantial source of good quality botanical data covering the entire region and freely accessible. To meet the needs for a regional data source, we created VegPáramo, a floristic and vegetation database containing 3000 vegetation plots sampled with the phytosociological method throughout the páramo region and proceeding from the existing literature and our fieldwork. We made VegPáramo accessible online through a webportal, www.vegparamo.com, from which the data can be freely consulted and downloaded. We then used the VegPáramo data to conduct a regional vegetation classification of the páramo. We used a clustering technique and classified the region into 17 clusters, 14 representing natural phytogeographical units of one or several plant communities and 3 artificial ensembles. We characterized the 17 clusters and estimated the alpha diversity and beta diversity to highlight species richness and floristic similarities. Our last study focused on the plant diversity patterns in the páramo region. We used the VegPáramo data and our classification results to estimate and compare plant diversity at local and regional scale in the altitudinal belts of the páramo. We evaluated the importance of the environment as driver of species richness using regression models. Finally, we modeled the predicted species richness in the páramo region and highlighted biodiversity hotspots. Our project contributes to a better understanding of the páramo biogeography and makes primarily suggestions for conservation. We believe further research should focus on the impacts of climate change on the páramo flora and vegetation.La región biogeográfica que incluye los ecosistemas naturales y semi-naturales de alta montaña distribuidos entre el bosque montano y las nieves perpetuas en los Andes del Norte recibe el nombre de páramo, el cual es considerado un hotspot de biodiversidad, con más de 3.400 especies de plantas vasculares y un alto grado de endemismo. La gran biodiversidad del páramo se debe en gran parte a su reciente origen y a su insularidad continental. Los páramos proporcionan muchos servicios ecológicos a las poblaciones humanas, sobretodo en el subministro de agua y el secuestro de carbono. Las actividades antrópicas como la agricultura y el pastoreo, y el cambio climático son las principales amenazas para el equilibrio ecológico del ecosistema. Consecuentemente, es imprescindible aumentar nuestro conocimiento científico y proponer nuevas estrategias de gestión y de conservación. La mayoría de estudios botánicos y ecológicos sobre el páramo, al igual que los planes de gestión, se desarrollan desde escala local hasta nacional. Aunque estos estudios son aportaciones de gran valor científico, también es importante considerar el ecosistema en toda su extensión para obtener unos resultados y patrones válidos en la región biogeográfica. Los estudios regionales sobre la biogeografía de plantas en el páramo son muy escasos, siendo las principales limitaciones la dificultad de establecer colaboraciones científicas y de gestión internacionales y la falta de fuentes de datos biológicos de buena calidad y de libre acceso. Consecuentemente, construimos VegPáramo, una base de datos de flora y vegetación para el páramo andino, que contiene 3.000 inventarios de vegetación muestreados con el método fitosociológico en la región, y que proceden tanto de la literatura como de nuestro trabajo de campo. Creamos un portal web para VegPáramo, www.vegparamo.com, a partir del cual se pueden consultar y descargar los datos libremente. Usamos los datos de VegPáramo para clasificar la vegetación de páramo a nivel de la región. Con una metodología de clustering no-jerárquico, clasificamos el páramo en 17grupos (o clusters) de los cuales 14 representan a unidades fitogeográficas naturales conteniendo una o varias comunidades vegetales y 3 son artificiales. Caracterizamos los 17 grupos por su flora diagnóstica y los comparamos a nivel de diversidad alpha y beta. Finalmente, usamos los datos de VegPáramo y los resultados de nuestra clasificación para estimar y comparar la diversidad de plantas a escala local y regional en los pisos altitudinales del páramo con el objetivo de destacar y entender los principales patrones de riqueza florística en la región. Evaluamos el poder explicativo del ambiente en la riqueza florística mediante modelos de regresión. Finalmente, modelamos la riqueza florística potencial en la región y destacamos unos hotspots de biodiversidad. Nuestro proyecto contribuye a entender mejor el páramo como región biogeográfica y propone primeras sugerencias de áreas concretas para la conservación. Pensamos que los esfuerzos futuros de investigación y de gestión deberían enfocarse particularmente en los impactos del cambio climático sobre la flora y la vegetación del páramo.
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Gerique, Zipfel Andrés Verfasser], and Perdita [Akademischer Betreuer] [Pohle. "Biodiversity as a resource : Plant use and land use among the Shuar, Saraguros, and Mestizos in tropical rainforest areas of southern Ecuador = Die Biodiversität als Ressource / Andres Gerique Zipfel. Betreuer: Perdita Pohle." Erlangen : Universitätsbibliothek der Universität Erlangen-Nürnberg, 2011. http://d-nb.info/1015475205/34.
45
Sultan, Gehan. "Impact d’une formulation minérale sur les composantes biologiques des sols agricoles." Thesis, Paris Est, 2011. http://www.theses.fr/2011PEST0103.
Abstract:
Des études récentes ont permis de constater qu'une part de plus en plus importante des sols agricoles présente des déficiences en micronutriments. Ces carences posent donc de graves problèmes en terme de productivité. Il existe de nombreuses études sur le rôle des micronutriments dans le métabolisme des plantes et des microorganismes. Cependant aucune étude basée sur une approche holistique visant à prendre en considération l'ensemble des trois composantes biologiques du sol (plante, faune, microorganismes) par rapport à l'apport de micronutriments n'a été entreprise à ce jour. L'objectif de cette étude était de préciser l'impact des micronutriments sur les trois composantes biologiques d'un sol en étudiant différents paramètres tels que la production de biomasse végétale, les communautés bactériennes et les aspects fonctionnels à travers l'analyse de l'activité des enzymes du sol.Une expérimentation menée en champ a été réalisée sur une culture de colza. Une comparaison entre blocs parcellaires traités et non traité a été réalisé en analysant le nombre et le poids de siliques ; la teneur en chlorophylle des feuilles, le poids et la densité des vers de terre, les activités enzymatiques, la structure des communautés microbiennes et l'activité microbienne globale. L'apport de micronutriments induit des changements de tous les paramètres biologiques étudiés en fonction du stade de développement de la plante. Parmi les enzymes étudiées (phosphatases alcaline et acide, beta-glucosidase, alpha-glucosidase, beta xylosidase), une augmentation significative de la phosphatase alcaline et de l'alpha-glucosidase a été mesurée mais seulement lorsque la plante est au stade de grenaison. A ce stade, on constate également une augmentation de l'activité microbienne totale ainsi qu'une plus forte densité de vers de terre dans les blocs parcellaires traités. De plus, l'apport de micronutriments affecte de manière significative les communautés de bactéries nitrifiantes mais ce phénomène ne s'observe qu'au stade de la floraison. L'ensemble des ces résultats suggère donc que les micronutriments agissent comme des catalyseurs de l'activité biologique des différents acteurs du sol (plante, microorganismes et macrofaune). Ils sont à l'origine d'une succession d'inter action complexes et modifient alors les processus biologiques qui s'opèrent dans le sol.Le deuxième objectif de cette étude était de comparer l'impact de micronutriments sur les communautés microbiennes en présence /absence de plantes ou de vers de terre. Une expérimentation conduite en microcosme a été entreprise. Compte- tenu que les paramètres physico –chimiques du sol influent la biodisponibilité des micronutriments, l'expérience a été réalisée avec trois types de sols (sols limoneux, argileux et sableux). Les résultats obtenus mettent en évidence que l'impacte des micronutriments sur les communautés bactériennes est subordonné à la présence et le type d'organismes (vers de terre/plante) ainsi qu'à la nature du sol.Finalement, les micronutriments ne doivent plus être perçus en terme de productivité à travers une simple relation avec la plante mais au contraire comme des agents agissant comme catalyseur de l'activité biologique des principaux acteurs du sol. Une telle vision holistique constitue les premières données pour établir les bases de l'agroécologieNumerous arable lands in the world have a low availability of micronutrients. This lack of micronutrients has a serious impact on crop production. To increase plant productivity more attention must be paid to micronutrients. A number of studies have focused on the effect of micronutrients on plant and bacterial metabolism. However, studies on the impact of these micronutrients, when all living organisms (plant, macrofauna and microorganism) present in a field are taken into account, are scarce..The aim of the present study was to investigate the effects of these micronutrients on the three soil components. Different parameters were chosen such as plant productivity, bacterial community, soil enzyme and fauna to determine the impact of micronutrients on these organisms.A field experimental approach consisted of micronutrient treatments during oilseed rape cultivation in the Aisne Department (France) was carried out. In comparison to control plots, the weight and number of siliques (seed pods), the chlorophyll content of leaves, the weight and density of earthworms, soil enzyme activities, bacterial communities and total microbial activity were analysed. The addition of micronutrients caused changes to all the biological parameters studied in relation to the plant growth stage. Among the enzymes tested (alkaline and acid phosphatase, beta-glucosidase, alpha-glucosidase, beta xylosidase), a significant increase in alkaline phosphatase and alpha-glucosidase was measured at the 3rd stage of oilseed rape development with the addition of micronutrients. At this stage of oilseed rape development, total microbial activity and the weight and density of earthworms were higher in plots under micronutrient treatment. On the other hand, micronutrients had a significant impact on the nitrifying bacterial community and the total bacterial community only at the 2nd stage of oilseed rape development. All these results suggest that micronutrients act as a catalyst by stimulating plants, soil fauna and microorganisms directly or indirectly. Thus micronutrients can modify biological processes in all living organisms through successive complex interactions.The second objective of this study was to compare the impact of micronutrients on bacterial communities in presence/absence of plants or earthworms. An in vitro experimental approach using microcosms has been conducted to study different parameters (bacterial community, soil enzyme activity, total microbial activity). Because characteristics of soil contents are important in determining the availability of micronutrients in soils the experiment was conducted on three type of soil: sandy; loamy and clay soil. Our results bring to light that the application of micronutrients affected the bacterial communities. However the nature and the importance of this impact varies according to the organisms presents (plant or earthworms) and the nature of the soil.The results of this study provide a scientific basis for fertilizing and utilizing soil, protecting microbial diversity, and accomplishing the sustainable development of agroecology
46
Onial, Malvika. "Responses of biodiversity to agricultural intensification : a study in the upper Gangetic Plain, India." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609391.
47
Hauser, James W. "Effects of hydrology-altering site preparation and fertilization/release on plant diversity and productivity in pine plantations in the coastal plain of Virginia." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-05042010-020225/.
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Stein, Claudia. "Biodiversity and ecosystem functioning: regional and local determinants of plant diversity in montane grasslands /." Leipzig : UFZ, 2008. http://www.ufz.de/data/ufzdiss_11_2008_9590.pdf.
49
Bryant, Jonathan. "The effects of increasing atmospheric nitrogen deposition and carbon dioxide on the growth and physiology of component species of the chalk grassland plant community." Thesis, University of Sussex, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266449.
50
Damestoy, Thomas. "Interactions entre les chênes et la chenille processionnaire du chêne, Thaumetopoea processionea L. : de l’arbre à la forêt." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0220/document.
Abstract:
Les forêts fournissent de nombreux services écosystémiques qui peuvent être compromis par les insectes. Le maintien de la santé des forêts est un enjeu majeur de la gestion forestière qui nécessite l’acquisition de connaissances sur les interactions arbres-ravageurs. Dans ce contexte, nous nous sommes focalisés sur la question de la résistance des chênes à un ravageur, la chenille processionnaire du chêne (CPC).La CPC est un herbivore spécialiste des chênes décidus en Europe. Elle est responsable de fortes défoliations, en plus de graves urtications chez les usagers de la forêt. Au travers d’une série d’observations et d’expériences menées à plusieurs niveaux d’intégration (de l’arbre jusqu’à la forêt), nous nous sommes intéressés à la réponse de la CPC à différents facteurs écologiques intervenant dans la résistance des arbres : la composition du peuplement, le voisinage et les traits foliaires liés à la défense.La résistance des arbres aux herbivores est influencée par la composition des forêts. Pour une espèce donnée, les arbres subissent en général moins d’attaques dans les mélanges que dans les peuplements purs (résistance par association). Nous avons testé l’effet des associations entre espèces d’arbres sur la résistance des chênes à la CPC, en comparant l’abondance des adultes et les dégâts des larves sur le chêne pédonculé (Quercus robur) et le chêne sessile (Q.petraea) dans des peuplements purs ou mélangés. Nous avons exploré les mécanismes sous-jacents, en recherchant les traits foliaires des chênes impliqués dans la variabilité des performances de la CPC. Enfin, nous nous sommes interrogés sur les causes génétiques et environnementales de la variabilité interindividuelle dans l’expression de ces traits.Premièrement, nous avons mis en évidence une plus grande susceptibilité de Q.petraea, caractérisée par une plus grande attractivité de Q.petraea pour les papillons de CPC, un niveau de défoliation plus élevé et une plus grande survie et prise de poids des larves sur cette essence. Nous avons aussi mis en évidence une plus grande susceptibilité des chênes dans les peuplements purs par rapport aux peuplements mélangés, en particulier ceux associant un chêne à une autre essence non hôte. Ensuite, nous avons étudié les mécanismes conférant une plus grande résistance à Q.robur et aux peuplements mélangés, en mesurant les traits foliaires (les défenses chimiques et la phénologie). La synchronisation entre le développement des feuilles et celui des larves est apparue comme un facteur clé déterminant les performances de la CPC. La concentration des défenses chimiques dans les feuilles était positivement corrélée au taux de consommation des feuilles par les chenilles, suggérant une compensation alimentaire pour maintenir la croissance sur les feuilles les plus défendues. Nous avons montré que l’expression de ces traits était influencée par l’identité des voisins. Enfin, chez Q.robur, nous avons montré l’existence d’un contrôle génétique de l’arbre sur les performances des chenilles.L’ensemble des résultats permet de mieux comprendre les processus impliqués dans l’effet du mélange d’essences sur les dégâts d’insectes et apporte des éléments permettant d’orienter la gestion des peuplements de chênes pour une meilleure résistance à la CPC. Au vu de ces résultats, il semblerait préférable de favoriser Q.robur pour sa moindre attractivité et sa plus grande résistance à la CPC. Cette proposition va toutefois à l’encontre des préconisations d’utilisation de Q.petraea pour adapter les chênaies au risque de déficit hydrique et ne fait que rajouter un élément de complexité à la gestion de la résistance des forêts face à des perturbations multiples en interaction. A l’aune de la mise en évidence de l’effet du génotype de l’arbre et de ses traits foliaires dans le développement de la CPC, la caractérisation des gènes et des molécules de défenses impliquées reste un champ de recherche quasi inexplorée, qu’il conviendra de défricherForest ecosystems provide a series of ecosystem services that can be threatened by pest insects. Maintaining forest health is therefore a major challenge of forest management that requires a sound understanding of tree-pest interactions. In this context, we investigated oak resistance (and its drivers) to a pest insect, the oak processionary moth (OPM), Thaumetopoea processionea.The OPM is a specialist herbivore feeding on oaks in Europe. It is responsible for significant defoliation, in addition to serious urtication in forest users and practitioners. Through a series of observations and experiments carried out at several levels of integration (from tree to forest stand levels), we investigated the response of this insect to various ecological factors involved in oak resistance: forest stand species composition, tree neighbourhood effects and leaf traits potentially associated with defence.Forest species composition has well documented effects on tree resistance to herbivores. For a given species, trees are generally less attacked in mixtures than in pure stands (i.e. associational resistance). But the opposite - associational susceptibility - also exists. We tested whether tree species diversity generated associational resistance to OPM, by comparing abundance and damage on the pedunculate (Quercus robur) and sessile oaks (Q. petraea) in pure and mixed stands. We also investigated the underlying mechanisms, by characterizing the leaf traits involved in the variability of OPM performance. Finally, we focused on the genetic and environmental causes of inter-individual variability in the expression of these traits.First, we found that Q. petraea was generally more susceptible to the OPM than Q. robur. Stands dominated by Q. petraea attracted more OPM moths, Q. petraea suffered more defoliation, and OPM larvae had greater survival and weight gain on this species. We also found greater susceptibility of both oak species in pure stands as compared to mixed stands, particularly those associating an oak with another non-host species. Second, we investigated the mechanisms conferring greater resistance to Q. robur and to mixed stands by quantifying leaf chemical and developmental traits involved in oak-OPM interactions. The synchronization between leaf development and larval development also appeared to be a key factor determining the OPM performance. The concentration of leaf chemical defences was positively correlated with OPM consumption rate, suggesting a compensatory feeding response to maintain OPM growth rate on well-defended leaves. Leaf traits involved in oak-OPM interactions were partially determined by the identity of oak neighbours. Third, we found evidence that OPM performance was partially under the genetic control of their host trees in Q. robur.Overall, these results built toward a better understanding of the processes involved in the effect of tree species mixture on the damage caused by pest insects and provide new avenues to guide oak stand management for improved resistance to OPM. Based on the results of this study, it would seem preferable to favour Q. robur in oak stands because it is less attractive and more resistant to OPM attacks, both in the field and in the laboratory. However, this statement goes against current recommendations to use Q. petraea to adapt the oak to the increased risk of water deficit and therefore adds to complexity of managing forests for resistance to multiple-interacting stresses