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1
Ložytė, Aurelija. "The influence of agri-environmental measures based grassland management on grassland plant communities." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2014. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2014~D_20140526_082518-10331.
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Grassland is an important component of agrarian landscape, performing wide range of ecological, economic and social functions. Long-term changes of the conditions of habitats, determined by human economic activities, influence the state of grassland plants. Rural Development Programme for Lithuania 2007–2013 sets measure to preserve biological diversity of grassland. The purpose of it is to reduce negative anthropogenic effect on grassland plant communities using the EU funds. Having researched the differences of grassland plant diversity and economic value, influenced by different intensity economic activities, the main objective of this paper is to evaluate the efficiency of EU regulated, agri-environmental measures based, grassland management methods in small farming sector of Lithuania. The research, involving the assessment of the number of plant species, diversity of plant families, distribution of relative plant abundance, and dominance of plant species in plant communities in grassland managed traditionally and according to the requirements of agri-environmental farming, showed that both types of grassland had similar plant communities. Such conclusion was drawn from the analysis of Jaccard and Sörensen similarity coefficients. The difference of plant adaptation to soil dampness, acidity, and nutrition was not statistically significant in grasslands of both types. Most of the plants in grassland researched were mesophytes; soil acidity was not a determining factor to... [to full text]Pievos yra svarbus agrarinio kraštovaizdžio komponentas, atliekantis įvairias ekologines, ekonomines ir socialines funkcijas. Ilgalaikiai augaviečių sąlygų pokyčiai, kuriuos lemia žmogaus ūkinė veikla, įtakoja pievų augalų būklę. Lietuvos kaimo plėtros 2007–2013 m. programoje numatyta priemonė pievų biologinės įvairovės išsaugojimui, kurios tikslas panaudojant ES lėšas mažinti neigiamą antropogeninį poveikį pievų augalų bendrijoms. Ištyrus pievų augalijos įvairovės ir ūkinės vertės skirtumus, sąlygotus skirtingos ūkinės veiklos intensyvumo, šio darbo tikslas įvertinti reglamentuotų, ES agrarinės aplinkosaugos priemonėmis paremtų, pievų tvarkymo metodų efektyvumą smulkiuose Lietuvos ūkiuose. Atliktas tyrimas parodė, kad įvertinus augalų rūšių skaičių, augalų šeimų įvairovę, augalų rūšių santykinio gausumo pasiskirstymą, dominuojančias augalų rūšis tradiciniais ir agrarinės aplinkosaugos reikalavimus atitinkančiais ūkininkavimo metodais tvarkomose pievose, nustatyta, kad jose augo panašios augalų bendrijos. Tai parodė ir Žakaro bei Sörensen bendrumo koeficientų reikšmės. Abiejų tipų pievose rastų augalų rūšių prisitaikymo prie dirvožemio drėgmės, rūgštingumo, turtingumo maisto medžiagomis rodiklių reikšmės statistiškai reikšmingai nesiskyrė. Pievų augalų bendrijose vyravo mezofitai, daugumai augalų rūšių dirvožemio rūgštingumas buvo neįtakojantis veiksnys, pievoms būdingi mezooligotrofiniai ir mezotrofiniai žolynai. Tyrimas parodė, kad biologinės įvairovės apsaugai palankus... [toliau žr. visą tekstą]
2
Toogood, Sarah Elizabeth. "Response of wet grassland plant communities to water regime." Thesis, University of Brighton, 2005. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413101.
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Moore, Joslin Lynley. "Coexistence, assembly and invasion of plant communities in theory and practice." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312122.
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Carlyle, Cameron Norman. "Interacting effects of climate change and disturbance on grassland plants and plant communities." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/42269.
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Grasslands are threatened by urbanization, agricultural conversion, over-grazing, tree-encroachment, and invasive plants. Simultaneously, climate change acts on all levels of biological organization, from entire communities to the physiology of individuals. The environmental stresses induced by climate change have the potential to interact with human-caused disturbance, but the response of plants to these stresses and disturbances, and how they may interact, are not well known. To conserve grasslands it is critical to know which types of grassland and which plant species will be most affected. To understand the mechanisms of change at the ecosystem level it is necessary to study the response at lower levels of biological organization. Using a variety of approaches I studied the potentially interacting effects of stress (primarily reduced water availability) and disturbance (plant biomass removal) on different levels of biological organization. I ran a 4-year field experiment in which I manipulated water availability, temperature and clipping in three different grassland types. I found complex plant community structure and biomass response; treatments often interacted but the different grassland types had their own particular responses. As part of this experiment I monitored the effects of treatments on soil moisture and temperature and found that the effects are generally consistent with expectations, but treatments do not act exclusively or independently on target variables. In addition to stress and disturbance, competition is a key process structuring grasslands. In the greenhouse, I examined how plant competition is affected by stress and disturbance. I found that the interpretation of how competition is affected is dependent on the way competition is measured. Some measures of competition showed reduced competition across stress and disturbance gradients, but other measures showed no change. Finally, I examined the root traits of 18 species of grass in the greenhouse in response to reduced water availability. I found significant variation in traits among species, maintenance of trait hierarchies across environments and little evidence of plasticity, except for root: shoot ratio. Overall, stress, disturbance and their interactions are important in influencing individual plant performance, competition, structuring plant communities, and ecosystem function.
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Innes, Louise. "Feedbacks between plant and soil microbial communities in temperate grassland." Thesis, Lancaster University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421621.
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Drobnik, Juliane [Verfasser], and Peter [Akademischer Betreuer] Poschlod. "Assembly rules in grassland plant communities / Juliane Drobnik. Betreuer: Peter Poschlod." Regensburg : Universitätsbibliothek Regensburg, 2011. http://d-nb.info/102336185X/34.
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Scherer-Lorenzen, Michael. "Effects of plant diversity on ecosystem processes in experimental grassland communities /." Bayreuth : Bayreuther Institut für Terrestrische Ökosystemforschung (BITÖK), 1999. http://www.gbv.de/dms/bs/toc/31133928x.pdf.
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Chu, Chengjin, Andrew R. Kleinhesselink, Kris M. Havstad, Mitchel P. McClaran, Debra P. Peters, Lance T. Vermeire, Haiyan Wei, and Peter B. Adler. "Direct effects dominate responses to climate perturbations in grassland plant communities." NATURE PUBLISHING GROUP, 2016. http://hdl.handle.net/10150/617187.
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Theory predicts that strong indirect effects of environmental change will impact communities when niche differences between competitors are small and variation in the direct effects experienced by competitors is large, but empirical tests are lacking. Here we estimate negative frequency dependence, a proxy for niche differences, and quantify the direct and indirect effects of climate change on each species. Consistent with theory, in four of five communities indirect effects are strongest for species showing weak negative frequency dependence. Indirect effects are also stronger in communities where there is greater variation in direct effects. Overall responses to climate perturbations are driven primarily by direct effects, suggesting that single species models may be adequate for forecasting the impacts of climate change in these communities.
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Bossenbroek, Jonathan Mark. "Spatial structure and scaling of beetle, bird and plant communities in North American grasslands." Access citation, abstract and download form; downloadable file 10.52 Mb, 2004. http://wwwlib.umi.com/dissertations/fullcit/3131657.
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Swanepoel, Barbara Anna. "The vegetation ecology of Ezemvelo Nature Reserve, Bronkhorstspruit, South Africa." Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-09142007-143511.
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Newman, Reginald Frank. "Vegetation recovery and plant diversity dynamics in grassland communities following herbicide treatment." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq29086.pdf.
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Thomson, Bruce Craig. "Plant Input Effects on the Diversity and Function of Grassland Bacterial Communities." Thesis, University of Newcastle upon Tyne, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485856.
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By decomposing organic matter, bacterial communities are essential for plant growth and ecosystem functioning. Conversely, aboveground plant communities are known to select for particular bacterial communities by depositing C resources of different palatability belowground. Aboveground communities are known drivers of bacterial community structure which in turn affects soil C cycling. However, the exact mechanisms and feedbacks of this intimate relationship remain unclear. This thesis examines the effects of vegetation on bacterial community structure and whether plant driven differences in bacterial community composition affect soil C cycling and substrate utilisation in a grassland soil at the NERC experimental field site, Sourhope, Scotland. Firstly, the effects of vegetation on bacterial community structure .and soil respiration were examined. Bacterial community structure and function were shown to differ depending on the presence or ab~nce of plants. Particularly, differences in the abundances of certain bacteria were observed and soil respiration rates were higher in vegetated soil 'compared to bare soil. These differences in soil CO2-C efflux were attributed to differences in the physiological traits of the dominant bacterial taxa. Next, an assessment of laboratory soil pre-treatments was carried out to establish a suitable microcosm design for analysing soil bacterial communities. The results from this study were then implemented in the design of subsequent experiments to investigate soil bacterial community structure and C functional responses to added substrates. Using soil microcosms it was then investigated whether plant-induced differences in bacterial community structure affected the decomposition of different substrate types and amounts. Also, whether the presence or absence of plants selected for different bacterial community members responsible for the decomposition of labile and recalcitrant substrates added at a high and low concentration. Functional responses were shown to differ depending on soil type, substrate complexity and loading rate. Respiration responses were thought to be due to differences in bacterial community structure between soil treatments. Taxonomic responses also differed depending on the presence or absence of plants, decomposability of substrate and concentration. However, there were no consistent patterns in community changes. Finally, 13C-Iabelled substrates were added to soil with or without vegetation to accurately measure substrate specific respiration and assess priming effects. Also rRNASIP was performed in an attempt to unambiguously identify bacteria responsible for the assimilation of labelled substrates. Following labelled-substrate additions, mineralisation of substrates differed between soil treatments and was dependent on substrate type. Priming effects were strongest in bare soil as in vegetated soil added substrate was preferentially mineralised over native SOM. Both substrate specific respiration and priming effects were thought to be linked to bacterial community composition. Whilst all substrates were rapidly mineralised and significant differences existed between vegetated and bare soils, 13C was not incorporated into RNA with similar efficiency. Using rRNASIP the entire bacterial community in vegetated and bare soils was shown to have utilised 13C-substrates as a general bacterial community shift into enriched gradient fractions was observed. However, similar to initial bacterial diversity, there were differences in the abundances of functionally active bacteria between vegetated and bare soils.
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Heard, Matthew Spencer. "The role of invertebrate herbivory and plant competition in structuring mesic grassland communities." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390618.
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Holland, John Peter. "Plant herbivore interactions within a complex mosaic of grassland, mire and montane communities." Thesis, University of Glasgow, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342041.
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Johansson, Per. "Effects of habitat conditions and disturbance on lichen diversity : studies on lichen communities in nemoral, boreal and grassland ecosystems /." Uppsala : Dept. of Conservation Biology, Swedish University of Agricultural Sciences, 2006. http://epsilon.slu.se/200606.pdf.
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Viketoft, Maria. "Soil nematode communities in grasslands : effects of plant species identity and diversity /." Uppsala : Dept. of Ecology, Swedish University of Agricultural Sciences, 2007. http://epsilon.slu.se/200748.pdf.
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Glimskär, Anders. "Growth strategies, competition and defoliation in five grassland plants /." Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5465-4.pdf.
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Palisaar, Jaan. "The floodplain meadows of Soomaa National Park, Estonia vegetation - dispersal - regeneration /." Connect to this title online, 2006. http://www.opus-bayern.de/uni-regensburg/volltexte/2006/705/.
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Windhager, Steven. "An assessment of the use of seeding, mowing, and burning in the restoration of an oldfield to tallgrass prairie in Lewisville, Texas." Thesis, Connect to this title online, 1999. http://www.library.unt.edu/theses/open/19992/windhager%5Fsteven/index.htm.
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Currie, Gwen. "The impact of megaherbivore grazers on grasshopper communities via grassland conversion in a savannah ecosystem." Bachelor's thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/24945.
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Grasshoppers are sensitive indicators of the state of disturbance of grassland ecosystems. This study examined the grasshopper communities inside a game reserve, comparing those found on frequently grazed areas with communities inside plots that exclude megaherbivores. The vegetation inside the protected plots was found to differ from the openly grazed areas in terms of grass height and aerial cover, but not in % greenness or richness of forb species. Grass species varied with locality rather than grazing impact. Total numbers of grasshoppers did not differ significantly between the two contrasting areas (100.2 in vs 93.5 out), however grasshopper species richness did, with the outside, short-grass plots having on average 17 different species, and the inside tall-grass plots a higher mean of 24.5. Grasshopper communities responded primarily to grass height and vegetation cover, but not to grass species or greenness of vegetation.
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McDonald, M. Christine, of Western Sydney Hawkesbury University, and Faculty of Agriculture and Horticulture. "Ecosystem resilience and the restoration of damaged plant communities : a discussion focusing on Australian case studies." THESIS_FAH_HOR_McDonald_M.xml, 1996. http://handle.uws.edu.au:8081/1959.7/683.
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An examination was undertaken of the literature and restoration cases for 4 major Australian vegetation types (sclerophyll; rainforest; grassland; and wetland) to explore the proposition that ecological resilience may govern recovery after anthropogenic damage, and/or provide a fundamental guide and measure of success for ecological restoration. Also, primary data were collected from highly degraded sites (5 sclerophyll, 3 rainforest, and 4 grassy sites) to assess recovery after restoration treatment. These were supplemented with questionnaire data from practitioners working at a wider range of rainforest and sclerophyll sites, and reports from practitioners working on grassland and wetland sites. In all 4 vegetation types, species generally fell into two main groups : longer-lived 'resprouters' and shorter-lived 'obligate seeders'. But different resilience models were identified for the 4 vegetation types. The sclerophyll type exhibited higher in situ resilience but lower migratory resilience than the rainforest type, which was facilitated by flying frugivore dispersal to perch trees. Self-perpetuation was more tightly coupled with disturbance in the sclerophyll, grassland and wetland types than rainforest; and therefore 'designed disturbance' played a more obvious role in enhancing recovery within these types, than in rainforest. Results suggest that resilience (as both an ecosystem property and a theoretical concept) is fundamental to the practice of ecological restoration. Some prediction of resilience potential of particular degraded sites (and prediction of the degree and type of restoration subsidy needed) can be based on knowledge of : individual species' recovery mechanisms; resilience models for individual vegetation-types; and the site's colonisation potential and impact historyDoctor of Philosophy (PhD)
22
Jeffs, Christopher. "Natural enemies and the diversity of plant communities." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:49c80db9-6590-4e06-b86f-24d225046969.
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The processes that determine the structure of plant communities are of considerable practical and theoretical interest. Natural enemies such as herbivores, seed predators and pathogens provide one potentially important influence on plant diversity. I investigated the effects of natural enemies on plant diversity in two contrasting, species-rich plant communities (tropical forests in Panama and temperate grasslands in the UK), focusing on pre-dispersal seed predation by insects, and the mortality of seeds and seedlings caused by soil fungi. In Panama I found that pre-dispersal insect seed predators generate significant levels of mortality in multiple tropical tree species, with high heterogeneity in predation rates among individuals and at different forest sites. Insect seed predators were highly host-specific, consistent with a role in enhancing plant diversity. At Upper Seeds, a calcareous grassland site in the UK, I used manipulative experiments to show that soil fungi increase the diversity of plants propagating from soil seed banks. A parallel experiment in Panama, mimicking germination under light gap conditions, revealed differential effects of fungi among sites, with fungicide treatment appearing to increase the diversity of propagated seedlings at some sites but reducing it at others. These results suggest that the influence of soil fungi on pre-emergence mortality can alter plant diversity, even when post-emergence mortality from fungal pathogens is limited. In Panama, I also tested whether enemy-mediated mortality increases with rainfall, potentially contributing to the positive regional correlations widely observed between precipitation and plant diversity. In contrast to predictions, neither pre-dispersal insect seed predation nor the influence of soil fungi on seedling recruitment were affected significantly by site humidity, or (for soil fungi) with experimentally manipulated soil moisture levels. Overall, my results provide evidence that pre-dispersal seed predators and soil fungi can affect plant recruitment and diversity at early life stages, with potential consequences for the community structure of adult plants.
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Lawless, Patrick Joseph. "XERIC LIMESTONE PRAIRIES OF EASTERN UNITED STATES." View online, 2005. http://lib.uky.edu/ETD/ukybiol2005d00321/Lawless.pdf.
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Pfaff, Eric. "Patterns of grassland, shrubland, and woodland vegetation abundance in relation to landscape-scale environmental and disturbance variables, Applegate Watershed southwest, Oregon /." View full-text version online through Southern Oregon Digital Archives, 2007. http://soda.sou.edu/awdata/070406z1.pdf.
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Thesis (M.S.)--Southern Oregon University, 2007Computer printout. Includes bibliographical references (leaves 49-53). Also available via Internet as PDF file through Southern Oregon Digital Archives: http://soda.sou.edu. Search Bioregion Collection.
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McDonald, M. Christine. "Ecosystem resilience and the restoration of damaged plant communities : a discussion focusing on Australian case studies /." View thesis, 1996. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030625.095246/index.html.
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Johnson, Tracey N. "Ecological restoration of tallgrass prairie: grazing management benefits plant and bird communities in upland and riparian habitats." Thesis, Manhattan, Kan. : Kansas State University, 2006. http://hdl.handle.net/2097/190.
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Shahzad, Tanvir. "Role of plant rhizosphere across multiple species, grassland management and temperature on microbial communities and long term soil organic matter dynamics." Phd thesis, AgroParisTech, 2012. http://pastel.archives-ouvertes.fr/pastel-00772440.
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It is increasingly being recognized that the soil microbes can mineralize recalcitrant soil organic matter (SOM) by using the fresh carbon (C) as a source of energy, a process called priming effect (PE). It has been shown mostly in lab incubations that PE can have important consequences for sequestration of organic C in soils. However, the importance of PE in C and N dynamics of ecosystems remains little known. The soil-plant interactions and rhizospheric processes can modulate the rates of PE and its consequences on C and N dynamics in an ecosystem. The objective of this thesis was to determine the role of PE in the C and N dynamics of permanent grasslands and the modulation of this role in response to management (plant clipping, fertilization) and global warming. Moreover, it was aimed to identify the microbial groups involved in PE and to unravel the way, e.g. absorption of N, root exudations and litter deposition, by which plant can induce PE. The thesis was based on a new approach allowing continuous dual labelling of multiple grassland plants with 13C- and 14C-CO2. The dual labelling permitted the separation of soil-derived CO2 from plant-derived CO2, the calculation of PE and the determination of mean age of soil-derived CO2-C. Moreover, phospholipids fatty-acids analysis (PLFA) permitted to correlate the variation of PE with changes in microbial community composition. Our work showed that the increased SOM mineralization under grasses was consistently two to three times more than that in bare soils (i.e. PE) over long term (511 days). This reveals that the PE plays key role in ecosystem CO2-C flux and indicates that a very large pool of SOM is under the control of PE. Moreover, we report that 15,000 years old organic C from an undisturbed deep soil can be mineralized after the supply of fresh C by living plants to soil microbes. This result supports the idea that the SOM in deep soils is stable due to the energy-limitation of microbes and the 'inert' pool of organic C defined in current models is not so 'inert' finally. The supply of N in soil-plant system through the use of fertilizer or legume decreased the PE suggesting that the C storage in soils is limited by nutrient supply. Similarly, plant clipping reduced the plant N uptake thereby PE. Collectively these results suggest synchronization between plant N uptake and SOM mineralization supporting the idea that soils under permanent plant cover function as a bank of nutrients for the plant, maximizing plant productivity and nutrient retention. An innovative method clearly showed that the root exudation is the major way by which grassland plants induce PE. Moreover, saprophytic fungi are suggested as the key actors in the mineralization of recalcitrant SOM & PE. Lastly, we developed a new theory on temperature response of SOM mineralization by taking into account the energy-limitation of microbes and the temperature-dependent inactivation of enzymes. This theory predicts a negative relationship between temperature and mineralization of recalcitrant SOM, which was supported by experimental results. This finding challenges the classical paradigm of positive relationship between temperature and recalcitrant SOM mineralization. Overall, these investigations on plant-soil systems reinforce the idea that PE and underlying mechanisms play a key role in ecosystem C and N dynamics and even suggest that this role was underestimated in lab experiments.
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Wemheuer, Franziska Verfasser], Stefan [Akademischer Betreuer] Vidal, and Rolf [Akademischer Betreuer] [Daniel. "Influence of Grassland Management and Herbivory on Diversity and Ecology of plant-associated Bacterial Communities / Franziska Wemheuer. Gutachter: Stefan Vidal ; Rolf Daniel. Betreuer: Stefan Vidal." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2015. http://d-nb.info/1071991655/34.
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Rothenwöhrer, Christoph [Verfasser], Teja [Akademischer Betreuer] Tscharntke, Stefan [Akademischer Betreuer] Vidal, and Stefan [Akademischer Betreuer] Scheu. "Plant-herbivore-predator communities and grassland management intensity - Implications for biodiversity conservation practices on local and landscape scales / Christoph Rothenwöhrer. Gutachter: Stefan Vidal ; Stefan Scheu. Betreuer: Teja Tscharntke." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2013. http://d-nb.info/1044048131/34.
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Ložytė, Aurelija. "Agrarinės aplinkosaugos priemonėmis paremtų tvarkymo metodų įtaka pievų augalų bendrijoms." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2014. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2014~D_20140526_082534-19976.
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Pievos yra svarbus agrarinio kraštovaizdžio komponentas, atliekantis įvairias ekologines, ekonomines ir socialines funkcijas. Ilgalaikiai augaviečių sąlygų pokyčiai, kuriuos lemia žmogaus ūkinė veikla, įtakoja pievų augalų būklę. Lietuvos kaimo plėtros 2007–2013 m. programoje numatyta priemonė pievų biologinės įvairovės išsaugojimui, kurios tikslas panaudojant ES lėšas mažinti neigiamą antropogeninį poveikį pievų augalų bendrijoms. Ištyrus pievų augalijos įvairovės ir ūkinės vertės skirtumus, sąlygotus skirtingos ūkinės veiklos intensyvumo, šio darbo tikslas įvertinti reglamentuotų, ES agrarinės aplinkosaugos priemonėmis paremtų, pievų tvarkymo metodų efektyvumą smulkiuose Lietuvos ūkiuose. Atliktas tyrimas parodė, kad įvertinus augalų rūšių skaičių, augalų šeimų įvairovę, augalų rūšių santykinio gausumo pasiskirstymą, dominuojančias augalų rūšis tradiciniais ir agrarinės aplinkosaugos reikalavimus atitinkančiais ūkininkavimo metodais tvarkomose pievose, nustatyta, kad jose augo panašios augalų bendrijos. Tai parodė ir Žakaro bei Sörensen bendrumo koeficientų reikšmės. Abiejų tipų pievose rastų augalų rūšių prisitaikymo prie dirvožemio drėgmės, rūgštingumo, turtingumo maisto medžiagomis rodiklių reikšmės statistiškai reikšmingai nesiskyrė. Pievų augalų bendrijose vyravo mezofitai, daugumai augalų rūšių dirvožemio rūgštingumas buvo neįtakojantis veiksnys, pievoms būdingi mezooligotrofiniai ir mezotrofiniai žolynai. Tyrimas parodė, kad biologinės įvairovės apsaugai palankus... [toliau žr. visą tekstą]Grassland is an important component of agrarian landscape, performing wide range of ecological, economic and social functions. Long-term changes of the conditions of habitats, determined by human economic activities, influence the state of grassland plants. Rural Development Programme for Lithuania 2007–2013 sets measure to preserve biological diversity of grassland. The purpose of it is to reduce negative anthropogenic effect on grassland plant communities using the EU funds. Having researched the differences of grassland plant diversity and economic value, influenced by different intensity economic activities, the main objective of this paper is to evaluate the efficiency of EU regulated, agri-environmental measures based, grassland management methods in small farming sector of Lithuania. The research, involving the assessment of the number of plant species, diversity of plant families, distribution of relative plant abundance, and dominance of plant species in plant communities in grassland managed traditionally and according to the requirements of agri-environmental farming, showed that both types of grassland had similar plant communities. Such conclusion was drawn from the analysis of Jaccard and Sörensen similarity coefficients. The difference of plant adaptation to soil dampness, acidity, and nutrition was not statistically significant in grasslands of both types. Most of the plants in grassland researched were mesophytes; soil acidity was not a determining factor to... [to full text]
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Edwards, Grant R. "The creation and maintenance of spatial heterogeneity in plant communities : the role of plant-animal interactions." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239335.
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Cantero, Juan José. "Plant community diversity and habitat relationships in central Argentina grasslands /." Tartu : Tartu University Press, 1999. http://bibpurl.oclc.org/web/19977.
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Barbe, Lou. "Conséquences de l'assemblage des communautés végétales sur la décomposition de leur litière." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1B040/document.
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Au cours de son assemblage, une communauté végétale va subir de nombreux changements : immigration de nouvelles espèces de plantes possédant de nouveaux traits, disparition de certaines espèces de plantes avec d’autres traits, immigration de nouveaux organismes associés aux plantes (insectes, champignons…), changements de traits chez les espèces présentes… Tous ces changements sont susceptibles de modifier la décomposition de la litière produite par la communauté végétale. En effet, la décomposition de la litière est gouvernée par les traits des espèces végétales, par l’activité des organismes décomposeurs, et par le degré d’adaptation de ces organismes aux traits des espèces végétales. Cependant, les conséquences de l’assemblage de la communauté végétale pour la décomposition de la litière demeurent inconnues. L’objectif de cette thèse est de déterminer les conséquences de l’assemblage des communautés végétales prairiales sur la décomposition de leur litière, et ce à différentes échelles. Tout d’abord, nous avons étudié, très localement, les conséquences des plantes voisines que possèdent un individu pour la décomposition de sa litière (i.e. échelle intraspécifique). Nous avons distingué le cas où la litière de l’individu était seule, du cas où sa litière était mélangée à de la litière provenant d’autres espèces végétales. Puis, nous avons étudié les conséquences de l’assemblage sur la décomposition de la litière au niveau plus global de l’ensemble de la communauté végétale (i.e. échelle interspécifique). Enfin, nous avons exploré la rétroaction de la décomposition sur l’assemblage de la communauté. Deux grandes démarches expérimentales ont été développées, la première utilisant un dispositif de mésocosmes permettant de manipuler le voisinage local des individus, la seconde utilisant un dispositif Long Term Ecological Research (LTER) impliquant un vaste réseau de prairies avec différentes durées d’assemblage. À l’échelle locale, nos résultats indiquent qu’un individu qui possède des plantes voisines fonctionnellement dissemblables produit une litière plus décomposable et peut également abriter des décomposeurs plus efficaces. Lorsque la litière de cet individu est mélangée avec de la litière d’autres espèces, la décomposition du mélange est accélérée par des effets synergiques lorsque les plantes voisines sont évolutivement dissemblables et fonctionnellement éloignées du mélange. À l’échelle globale de l’ensemble de la communauté, nos résultats indiquent que tout au long de l’assemblage, de nombreux changements de traits fonctionnels des espèces végétales ont lieu (ratio C:N foliaire, teneur en matière sèche des feuilles, etc.) ainsi que des changements dans la composition de la communauté de décomposeurs (ratio C:N microbien). Ces changements impactent fortement la décomposition de la litière de la communauté prairiale mais s’annulent, maintenant le même taux global de décomposition. Enfin, nos résultats indiquent que plus la litière de couples d’espèces se décompose vite, notamment via des effets synergiques, plus ces espèces coexistent entre elles. Cette thèse met en évidence l’influence majeure de l’assemblage des communautés végétales prairiales sur la décomposition de leur litière, de l’invidu jusqu’à la communauté végétale toute entière. L’assemblage des communautés végétales peut donc influencer les processus écosystémiques d’après-vie tels que la décomposition de la litière. Cette influence se produit via les traits des plantes et l’activité de leurs décomposeurs. En retour, la décomposition de la litière impacte l’assemblage de la communauté végétale. La décomposition de la litière ne semble donc pas une conséquence collatérale des traits des espèces végétales, mais bien un élément important de leur stratégie écologique et de leurs interactions biotiques, situé au coeur d'une boucle de rétroaction avec les processus d'assemblage des communautésDuring its assembly, a plant community will be strongly modified: immigration of new plant species with new traits, disappearance of particular species with other traits, immigration of new plant-associated organisms (insects, fungi…), trait changes in existing species… All these changes are likely to drive the decomposition of litter produced by the plant community. Litter decomposition is indeed controlled by plant traits, activity of decomposer community, and adaptation of decomposer organisms to plant traits. However, the consequences of plant-community assembly on plant litter decomposition remain entirely unknown. This thesis aims at determining the consequences of plant-community assembly on plant litter decomposition, at distinct scales. First of all, we studied, locally, the consequences of neighboring plants on litter decomposition of plant individuals (i.e. intraspecific scale). We distinguished the case where litter of plant individuals was alone from the case where litter of plant individuals was mixed with litter from other species. Then we studied, more globally, the consequences of plant-community assembly on decomposition at the scale of the entire plant community (i.e. interspecific scale). Finally, we investigated whether plant litter decomposition feedbacks on plant-community assembly. We used two experimental approaches, the first one using a long-term mesocosm experiment for manipulating the local plant neighborhood of plant individuals, and the second one using of Long Term Ecological Research network involving grasslands with different time for assembly. At the local scale, our results indicate that plant individuals grown in functionally dissimilar neighborhood produce a more decomposable litter, and can also harbor more efficient decomposers. When the litter of these individuals is mixed with litter from other species, the decomposition of the litter mixture is accelerated by synergistic effects when neighboring plants are phylogenetically diverse, and functionnally dissimilar to the litter mixture. At the scale of whole plant community, our results show that numerous trait changes occur during assembly (leaf C:N ratio, leaf dry matter content…), as well as changes in the composition of the decomposer community (soil microbial C:N ratio). These changes strongly affect litter decomposition but offset each other, maintaining litter decomposition constant. Finally, our result show that the faster the decomposition of mixed-litter from two species is, the more both species coexist. This thesis demonstrates the major influence of plant-community assembly on plant litter decomposition in grassland ecosystems, from the scale of plant individuals to the scale of entire plant community. Plant-community assembly hence affects after-life ecosystem processes like litter decomposition. This influence occurs through plant traits and decomposer activity. In turn, litter decomposition feedbacks on plant-community assembly. Consequently, litter decomposition does not seem to be a collateral consequence of plant traits, but rather an important part of their ecological strategies and biotic interactions, participating to a feedback loop involving community assembly processes
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Sørensen, L. I. (Louise Ilum). "Grazing, disturbance and plant soil interactions in northern grasslands." Doctoral thesis, University of Oulu, 2009. http://urn.fi/urn:isbn:9789514291395.
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Abstract
Plants and soil organisms are closely linked. Plants are the sole source of carbon in the soil and soil organisms are responsible for recycling of nutrients, making them available for plant growth. To understand the function of a system, it is important to understand the interactions between the soil and plants. These interactions have mainly been studied in temperate areas, with few studies in the arctic and subarctic. The aim of this thesis was to investigate the effect of ecological disturbances in sub- and low-arctic grasslands on soil organisms and plant-soil feedback relationships. The effect of removal of vegetation, replanting of a local plant species, and different components of grazing (trampling, defoliation and return of nutrients) on soil decomposer organisms were studied. Whether short term effects of defoliation depended on plant species community was also studied, as well as whether defoliation in the field could create changes in the soil system systems that affect the growth of seedlings. Experiments were conducted under both controlled greenhouse conditions and in field sites.
The results showed that physical disturbance (removal of vegetation and trampling) reduced the abundance and diversity of soil biota. Defoliation increased soil decomposer abundance in the short term. Plant species composition did not affect soil biota and only in a few cases did it changes their responses to defoliation. In the long-term, effects of fertilization and defoliation on the soil biota were context-dependent. However, defoliation did create changes in the soil that reduced the growth of seedlings planted into the soil. Furthermore, plant species community and spatial heterogeneity (revealed by blocking) had important effects on the soil communities.
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Cochard, Arnaud. "Influence des facteurs paysagers sur la flore des habitats herbacés sous influence urbaine : approche taxonomiques et fonctionnelles." Thesis, Rennes, Agrocampus Ouest, 2017. http://www.theses.fr/2017NSARH102/document.
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Le processus d’urbanisation conduit à un ensemble de transformations et perturbations qui peuvent avoir des conséquences sur la flore spontanée. Ce travail de thèse porte sur les communautés végétales des espaces herbacés ordinaires distribués au sein 3 aires urbaines de l’ouest de la France : Angers, Nantes et la Roche-sur-Yon. A travers deux approches, taxonomique et fonctionnelle, l’objectif est d’analyser les variations de diversités et de composition floristiques le long de gradients paysagers (notamment d’urbanisation et de connectivité des habitats). Ces milieux apparaissent diversifiés, tout en ne présentant qu’un faible nombre d’espèces exotiques. Le gradient urbain-rural structure les communautés, établissant notamment de fortes distinctions dans leurs compositions spécifiques, et ce, malgré l’absence de variations en terme de richesse et d’homogénéisation. Ces distinctions sont en lien avec des traits relatifs à leurs exigences écologiques (habitat, pH, humidité, lumière)et au niveau de perturbation plus élevé en ville. Ces relations varient malgré tout selon que l’on considère l’abondance locale ou régionale des espèces suggérant que d’autres mécanismes viennent s’ajouter à ces processus de filtre. La mesure in situ de trois traits fonctionnels (hauteur, SLA et phénologie) montre également l’importance de ce processus de filtre sur les espèces à un niveau intraspécifique. L’ensemble des résultats montre la façon dont ces espèces communes s’assemblent au regard des processus écologiques à l’oeuvre dans des environnements urbains, et permet d’ouvrir des perspectThe process of urbanisation leads to a series of transformations and disturbances that may have consequences for wild plant communities. This thesis presents a study of the plant communities of ordinary grasslands distributed among three cities of western France: Angers, Nantes and La Roche-sur-Yon. Using both taxonomical and functional approaches, the aim is to analyse the variation in plant diversity and composition along landscape gradients, in particular those of urbanisation and habitat connectivity. Such grassland habitats appear to be diverse, despite a low number of exotic species. The urban-rural gradient structures such communities, in particular by strongly modifying species composition; and this despite an absence of variation in species richness or of homogenisation. These modifications in community structure are linked to traits for ecological requirements (for habitat, pH, humidity or light)or for adaptation to higher levels of disturbance in towns. These relationships vary according to species’ local or regional abundance, suggesting that other mecanisms accompany the filtering process. Taking into account three functional traits (height, SLA and phenology) measured in situ shows that the filtering process also has consequences at intraspecific level. Taken together, the results show how common species are assembled in response to ecological processes operating in urban environments and open up new perspectives and applications for the integration of grassland plant communities into biodiversity conservation objectives in urban areas
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Denyer, Joanne. "Interactions between rabbits, plants and soil and their consequences for chalk grassland and chalk heath vegetation communities." Thesis, University of Sussex, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.418720.
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De, almeida Tania. "Impact d’une espèce ingénieure de l’écosystème et son utilisation en restauration écologique : Le cas de Messor barbarus (L.) dans les pelouses méditerranéennes Above- and below-ground effects of an ecosystem engineer ant in Mediterranean dry grasslands Harvester ants as ecological engineers for Mediterranean grassland restoration: impacts on soil and vegetation A trait-based approach to promote ants in restoration ecology." Thesis, Avignon, 2020. http://www.theses.fr/2020AVIG0358.
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L’objectif principal de cette thèse était double : (i) mesurer l’impact d’une espèce de fourmi sur son écosystème, afin (ii) d’en déduire des applications potentielles dans le domaine de la restauration écologique.Les fourmis sont parmi les organismes les plus abondants des écosystèmes terrestres et occupent des zones géographiques très variées. Elles jouent des rôles écologiques clés dans de nombreux écosystèmes comme ingénieurs du sol, prédateurs ou régulateurs de la croissance et de la reproduction des plantes. Cependant les données collectées localement sont souvent parcellaires et ne permettent pas d’avoir une vision complète de l’impact d’une espèce sur son milieu.Messor barbarus (L.), connue pour redistribuer les graines et pour modifier les propriétés physico-chimiques du sol, est largement répandue dans le Sud-Ouest de l’Europe notamment au sein des pelouses méditerranéennes. Elle pourrait donc jouer un rôle majeur dans la composition et structuration de ces pelouses caractérisées par une forte biodiversité mais dont le nombre et la superficie ont drastiquement diminué ces dernières décennies.Dans un premier temps, par une étude multi-compartiments, nous avons confirmé l’hypothèse selon laquelle M. barbarus est une ingénieure de l’écosystème au sein des pelouses méditerranéennes. Elle transforme cet habitat en modifiant, comme attendu, les propriétés physico-chimiques du sol. Ces modifications sont associées à une augmentation de la biomasse et de l’hétérogénéité des communautés végétales ainsi qu’à des changements dans les faunes épigée et endogée (abondance, occurrence et structure des communautés). De plus, M. barbarus modifie profondément les relations trophiques et non trophiques interspécifiques et entre les espèces et leur habitat. L’hétérogénéité créée à l’échelle locale par l’activité de cette fourmi, entraine une diversification des niches écologiques au sein de ces pelouses.Malgré leur rôle souvent majeur sur le fonctionnement des écosystèmes, les fourmis ne sont que très rarement considérées en restauration écologique. Sur notre site d’étude, un chantier de réhabilitation d’une pelouse sèche après une fuite d’hydrocarbures et un transfert de sol, M. barbarus a permis d’accélérer la restauration des propriétés physico-chimiques du sol mais aussi de la banque de graines à moyen terme - sept ans après la réhabilitation du site. Ces résultats font donc de cette espèce une bonne candidate en ingénierie écologique.Afin de généraliser l’utilisation des fourmis en restauration écologique, nous proposons une méthodologie à destination des gestionnaires basée sur l’utilisation de traits fonctionnels et d’histoire de vie. Pour cela nous avons évalué le potentiel des fourmis en écologie de la restauration, puis nous avons listé l’ensemble des traits connus pour affecter les compartiments abiotiques et biotiques et/ou pertinent pour effectuer un suivi du succès de la phase de restauration. La méthodologie proposée permet une première sélection des espèces potentiellement utilisables en fonction des objectifs de restaurationThe main objective of this thesis was double: (i) to assess the impact of an ant species on its ecosystem, in order to (ii) deduce potential applications in the field of ecological restoration.Ants are among the most abundant organisms in terrestrial ecosystems and occupy a wide range of geographical areas. They play key ecological roles in many ecosystems as soil engineers, predators or regulators of plant growth and reproduction. However, the information collected locally is often fragmented and does not provide a complete overview of the impact of a species on its environment.Messor barbarus (L.), known to redistribute seeds and to modify the soil physico-chemical properties, is widespread in South-Western Europe, particularly in Mediterranean grasslands. Therefore, it may play a major role in the composition and structuring of these ecosystems, which are characterised by high biodiversity but whose abundance and surface area have decreased drastically in recent decades.Through a multi-compartment study, we confirmed the hypothesis that M. barbarus is an ecological engineer in Mediterranean grasslands. This species changes this habitat by modifying, as expected, soil physico-chemical properties. These modifications are associated with an increase in both biomass and heterogeneity of plant communities, as well as changes in above- and belowground fauna (abundance, occurrence and structure of communities). Messor barbarus profoundly changes trophic and non-trophic relationships within and between species and their habitat. The heterogeneity created locally by the activity of M. barbarus leads to a diversification of ecological niches within these grasslands.Despite their major role in the functioning of ecosystems, ants are rarely considered in restoration ecology. In our study site, corresponding to a dry grassland rehabilited after an oil leak and a soil transfer, M. barbarus contributed to accelerate the restoration of the soil physico-chemical properties but also of the seed bank in the medium term - seven years after the rehabilitation. These results make this species a good candidate for ecological engineering.In order to generalise the use of ants in restoration ecology, we propose a trait-based methodology for stakeholders. We evaluated the potential of ants in restoration ecology, then listed all the traits known to affect abiotic and biotic compartments and/or relevant to monitor the success of the restoration phase. The proposed methodology provides a first selection of potentially relevant species according to the restoration objectives
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Howe, Katherine Mitchell. "The ecology of invasions in a Minnesota grassland : characteristics of invasive species and invaded communities and the effects of global change /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/5266.
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Moulin, Thibault. "Modélisation mathématique de la dynamique des communautés herbacées des écosystèmes prairiaux." Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCD075/document.
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La modélisation dynamique des systèmes écologiques constitue une méthode incontournable pour comprendre,prédire et contrôler la dynamique des écosystèmes semi-naturels, qui fait intervenir des processuscomplexes. Le principal objectif de cette thèse est de développer un modèle permettant de simuler la dynamiqueà moyen terme de la végétation herbacée dans les prairies permanentes, en tenant compte à lafois de la productivité et de la biodiversité. Les prairies sont des réservoirs présentant une forte biodiversitévégétale, qui soutiennent de nombreux services écosystémiques. Sur le plan agricole, cette importantediversité contribue à la qualité de la production fourragère, et de plus, elle permet une plus grande résistancede la végétation face à des changements climatiques (réchauffement moyen, vagues de chaleur etde sécheresse).Pourtant, cette notion clé de biodiversité n’est que faiblement prise en considération dans la modélisationde l’écosystème prairial : elle est souvent absente ou alors présente sous une forme très simplifiée. Enréponse à ces considérations, ces travaux de thèse présentent la construction d’un modèle de successionbasé sur des processus, décrit par un système d’équations différentielles ordinaires, qui représente ladynamique de la végétation aérienne des prairies tempérées. Ce modèle intègre les principaux facteursécologiques impactant la croissance et la compétition des espèces herbacées, et peut s’ajuster à n’importequel niveau de diversité, par le choix du nombre et de l’identité des espèces initialement présentes dansl’assemblage. Ce formalisme mécaniste de modélisation nous permet alors d’analyser les relations qui lientdiversité, productivité et stabilité, en réponse à différentes conditions climatiques et différents modes degestion agricole.[...]Ces résultats soulignent alors le besoin de prendre en compte le rôle clé joué par la biodiversité dansles modèles de l’écosystème prairial, de par son impact sur le comportement des dynamiques simulées.De plus, pour rendre correctement compte des interactions au sein de la végétation, le nombre d’espècesconsidéré dans le modèle doit être suffisamment important. Enfin, nous comparons les simulations devégétation de ce modèle à des mesures issues de deux sites expérimentaux, la prairie de fauche d’Oensingen,et le pâturage de Laqueuille. Les résultats de ces comparaisons sont encourageants et soulignentla pertinence du choix et de la représentation des processus écologiques clés qui composent ce modèlemécaniste.Ce travail de thèse propose donc un modèle, en total adéquation avec les besoins actuels en terme demodélisation de l’écosystème prairial, qui permet de mieux comprendre la dynamique de la végétationherbacée et les interactions entre productivité, diversité et stabilitéDynamic modelling of ecological systems is an essential method to understand, predict and control thedynamics of semi-natural ecosystems, which involves complex processes. The main objective of this PhDthesis is to develop a simulation model of the medium- and long-term dynamics of the herbaceous vegetationin permanent grasslands, taking into account both biodiversity and productivity. Grasslandecosystems are often hot spots of biodiversity, which contributes to the temporal stability of their services.On an agricultural perspective, this important biodiversity contributes to the forage quality, andbesides, it induces a higher ability of the vegetation cover to resist to different climatic scenarios (globalwarming, heat and drought waves).However, this key aspect of biodiversity is only poorly included in grassland models : often absent ofmodelling or included in a very simple form. Building on those considerations, this PhD work exposes thewriting of a process-based succession model, described by a system of Ordinary Differential Equationsthat simulates the aboveground vegetation dynamics of a temperate grassland. This model implementedthe main ecological factors involved in growth and competition processes of herbaceous species, and couldbe adjust to any level of diversity, by varying the number and the identity of species in the initial plantcommunity. This formalism of mechanistic models allows us to analyse relationships that link diversity,productivity and stability, in response to different climatic conditions and agricultural management.In mathematical grassland models, plant communities may be represented by a various number of statevariables, describing biomass compartments of some dominant species or plant functional types. The sizeof the initial species pool could have consequences on the outcome of the simulated ecosystem dynamicsin terms of grassland productivity, diversity, and stability. This choice could also influence the modelsensitivity to forcing parameters. To address these issues, we developed a method, based on sensitivityanalysis tools, to compare behaviour of alternative versions of the model that only differ by the identityand number of state variables describing the green biomass, here plant species. This method shows aninnovative aspect, by performing this model sensitivity analysis by using multivariate regression trees. Weassessed and compared the sensitivity of each instance of the model to key forcing parameters for climate,soil fertility, and defoliation disturbances. We established that the sensitivity to forcing parameters ofcommunity structure and species evenness differed markedly among alternative models, according tothe diversity level. We show a progressive shift from high importance of soil fertility (fertilisation level,mineralization rate) to high importance of defoliation (mowing frequency, grazing intensity) as the sizeof the species pool increased.These results highlight the need to take into account the role of species diversity to explain the behaviourof grassland models. Besides, to properly take into account those interactions in the grassland cover, theconsidered species pool size considered in the model needs to be high enough. Finally, we compare modelsimulations of the aboveground vegetation to measures from two experimental sites, the mowing grasslandof Oensingen, and the grazing grassland of Laqueuille. Results of these comparison are promising andhighlight the relevance of the choice and the representation of the different ecological processes includedin this mechanistic model.Thus, this PhD work offers a model, perfectly fitting with current needs on grassland modelling, whichcontribute to a better understanding of the herbaceous vegetation dynamics and interactions betweenproductivity, diversity and stability
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Bakker, Jan Pouwel. "Nature management by grazing and cutting on the ecological significance of grazing and cutting regimes applied to restore former species-rich grassland communities in the Netherlands." Dordrecht ; Boston : Kluwer Academic Publishers, 1989. http://catalog.hathitrust.org/api/volumes/oclc/18780741.html.
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Sennblad, Adina. "Effects of past fragmentation and habitat loss and current management methods on the changes in vascular plant communities. : An evaluation of extinction debt in semi-natural grasslands in Sweden." Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-447366.
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Habitat loss and fragmentation are believed to be two of the main reasons for high extinction rates of species, resulting in decreased biodiversity. According to the island biogeography theory, the species richness in a patch, here a semi-natural grassland, is dependent on the landscape composition, and therefore changes in the landscape composition will result in changes in the species richness of the grassland. However, this change in species richness may be delayed for several years, causing an extinction debt. The aim of this study was to examine the change of species richness of vascular plants in Swedish semi-natural grasslands between 2007 and 2020 and investigate if there is evidence of an extinction debt and evaluate what factors causes changes in the plant community. Data of species richness and occurrence for 40 semi-natural grasslands, as well as data of landscape changes in area and connectivity between the 1950:s and the 2000:s for these grasslands, were analysed. This study found that changes in species richness in semi-natural grasslands were affected by the changes in connectivity of the landscape. However, the effect depended on the degree of specialisation of the species to semi-natural grassland. Between 2007 and 2020, the species richness of semi- natural grasslands specialist decreased, while the species richness of non-specialist species increased. This resulted in a mean increase of overall species richness between 2007 and 2020. Observed immigration of new non-specialist species appears to suggest that, not only the connectivity, but also the habitat types in the matrix surrounding the semi-natural grasslands may substantially influence the species composition in the grassland; this is in contrast to what is predicted by the original theory of island biogeography. Species that were classified as specialist were more vulnerable to ceased management, such as grazing, than to area and connectivity decrease. This was likely because the ceased management increased the competition for light. The results also indicated that re-established management of abandoned grasslands may increase specialist species richness, highlighting the need for management actions taken in order to reverse extinction debt.
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Piton, Gabin. "Résilience des écosystèmes prairiaux aux stress climatiques selon l'intensité de gestion. Une approche par le concept de trait fonctionnel microbien Using proxies of microbial community‐weighted means traits to explain the cascading effect of management intensity, soil and plant traits on ecosystem resilience in mountain grasslands The resilience of soil microbial communities to climate change-induced rain regimes differs between conventional and ecological-intensive managed soils across European agroecosystems Implementing ecoenzymes in the trait framework bring new insights on the microbial communitiy composition control on ecosystem functioning." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAV070.
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Dans le contexte actuel du changement climatique et de l’augmentation de la fréquence et de l’intensité des épisodes climatiques extrêmes, une question centrale pour l’écologie scientifique est de comprendre les répercussions de ces changements sur le fonctionnement des écosystèmes. Les communautés microbiennes du sol contrôlent une grande partie des processus écosystémiques déterminant la circulation de l’énergie et des nutriments. Dans le cadre des agroécosystèmes se pose donc la question de l’influence des pratiques agricoles sur les communautés microbiennes du sol et sur leur aptitude à maintenir le fonctionnement des écosystèmes face au changement climatique. L’intensification écologique de l’agriculture a récemment été proposée comme une approche intégrant les processus écologiques dans la stratégie de gestion des agroécosystèmes, dans l’objectif d’optimiser leur fonctionnement et leur résilience. L’écologie fonctionnelle pourrait répondre à certains des enjeux posés par le changement climatique et l’intensification écologique de l’agriculture.Dans cette thèse, j’ai cherché à mobiliser le cadre conceptuel des traits fonctionnels pour apporter de nouveaux éléments de compréhension de l’influence de différentes modalités d’intensité de gestion d’agroécosystèmes prairiaux (gestion extensive, conventionnelle-intensive et écologiquement-intensive) : 1) sur les caractéristiques fonctionnelles des communautés microbiennes du sol; 2) sur la capacité de ces communautés microbiennes à maintenir le fonctionnement de l’écosystème face à des périodes de stress climatiques (résilience). Dans le cadre de ma thèse, trois expérimentations ont été réalisées en faisant varier le degré de contrôle des facteurs de gestion, le type de stress climatique et la durée de ces stress. S’appuyant sur des agroécosystèmes prairiaux répartis dans trois pays Européens (France, Suisse, Portugal), les résultats des deux premières expérimentations de cette thèse montrent que les communautés microbiennes des sols des prairies écologiquement-intensives disposent d’une plus faible capacité à maintenir les propriétés écosystémiques microbiennes durant les stress (faible résistance) mais disposent d’une meilleure capacité de récupération comparée aux communautés microbiennes des sols en gestion conventionnelle-intensive. Une autre étude montre que la gestion éco-intensive favorise des communautés microbiennes protéolytiques bénéfiques à l’assimilation de l’azote pour les plantes en conditions perturbés. L’étude des traits végétaux suggère que ces effets de la gestion sur la composition des communautés microbiennes et sur leur résilience passe par certains traits, notamment une augmentation de la richesse en phosphore des litières en gestion écologiquement-intensive. En effet ces traits fonctionnels des plantes semblent influencer les traits microbiens, favorisant des communautés microbiennes copiotrophes, caractérisées par un ratio azote:phospore faible de leur biomasse et un faible investissement dans la production d’enzymes extracellulaires, deux traits négatifs pour la résistance au stress mais favorisant une récupération rapide. Ainsi, ces deux expérimentations soulignent l’importance de la gestion des traits des plantes dans le contrôle des traits microbiens et de la résilience des écosystèmes au changement climatique. La troisième expérimentation a cherché à tester spécifiquement les effets d’un épisode de fertilisation minérale sur la résilience des communautés microbiennes à différents stress climatiques. Les résultats montrent que la fertilisation modifie la composition et les traits microbiens avec des répercussions négatives sur la stabilité de l’écosystème face à la sécheresse et à l’inondation.Mobilisant une approche par le concept de trait fonctionnel microbien, ce travail de thèse apporte de nouveaux éléments de compréhension des effets de l’intensité de gestion sur la résilience des écosystèmes prairiaux face aux stress climatiquesIn the current context of climate change, associated with increases of climate extremes frequency and intensity, understanding the ecosystem response to climate variability is a central challenge in ecology. Soil microbial communities control most ecosystem processes driving energy and nutrients fluxes. In the context of agriculture management, an important question is to understand the influence of farming practices on soil microbial communities and their capacity to maintain ecosystem functioning under climate change. Ecological-intensive agriculture has been recently proposed as an approach integrating ecological processes in management strategies to optimise agroecosystems functioning and resilience to climate change. Functional ecology might be relevant to address these challenges associated with climate change and ecological-intensification of agriculture.In this PhD thesis, I used the functional trait framework to grassland ecosystems to address how different modalities of management intensity (extensive, conventional-intensive, ecological-intensive management) influence: 1) functional parameters of soil microbial communities; 2) the capacity of these soil microbial communities to maintain ecosystem functioning during and after climatic stresses (Resilience). During my PhD, three experiments have been conducted using different degrees of control of management factors and simulating different kind of climatic stresses, with different durations. Based on grassland agroecosystems in three countries across Europe (France, Switzerland, Portugal), results from the first two experiments of this PhD showed that ecological-intensive management select soil microbial communities with a lower capacity to maintain microbial ecosystem properties during stresses (resistance) but with higher capacity to recover compared with soil microbial communities of soils under conventional-intensive management. Moreover, another study showed that ecological-intensive management promotes beneficial proteolytic soil microbial communities for plant nitrogen uptake under climate change-induced rain regimes. Plant functional traits assessment suggest this management effect on microbial communities composition and resilience to be explained by higher litter phosphorous content in ecological-intensive systems. Indeed, this plant functional trait affect microbial traits, favouring copiotrophic microbial community characterized by a lower nitrogen:phosphorous ratio of their biomass and a lower investment in extracellular enzymes production, two traits decreasing stress resistance but increasing recovery capacities. Thereby, these two experiments stress the relevance of plant traits management to control soil microbial traits and the resilience of soil microbial communities to climate changes. A third experiment tested specifically the impact of a mineral fertilisation event on the resilience of soil microbial communities to different climatic stresses. Results clearly demonstrated that fertilization modify soil microbial community composition and soil microbial traits and decrease ecosystem stability under climatic stresses.Implementing an approach based on the microbial functional trait concept, this thesis brings new insights on the effects of management intensity on grassland ecosystem resilience to climatic stress
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Limb, Ryan Frank. "The effects of disturbance in grassland plant communities." 2008. http://digital.library.okstate.edu/etd/Limb_okstate_0664D_10036.pdf.
Full text
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Macdonald, Catherine A. "Plant colonization of gopher mounds in adjacent pasture and prairie communities." Thesis, 1989. http://hdl.handle.net/1957/37645.
Full textAbstract:
I used field experiments to study how plants in two grassland communities colonized
soil mounds made by the Camas pocket gopher, Thomomys bulbivorus (Richardson). I
identified potential mound colonizers in each source of colonization (buried propagule bank,
seed rain, and established vegetation) and then measured species specific rates of
colonization on mounds built by T. bulbivorus. By selectively eliminating different avenues
of colonization on artificial mounds, I estimated the relative and combined effects of
colonization from (1) germination and growth of buried viable seeds and growth of root
fragments in the soil; (2) germination of seeds raining onto the mounds; (3) emergence of
buried vegetation and, (4) encroachment and establishment of adjacent vegetation. Artificial
mounds were good mimics of mounds built by T. bulbivorus judged by their similarity in
colonization rates and composition of colonizing species. I repeated the investigation in
adjacent pasture and prairie communities differing in species composition and abundances
to compare the effects of these differences on the colonization process.
Composition and abundance of species in the expressed and potential vegetation varied
considerably between pasture and prairie as did the two communities' response to identical
gopher disturbances. Percent cover of vegetation on mounds increased 3 times faster in the
Composition and abundance of species in the expressed and potential vegetation
varied considerably between pasture and prairie as did the two communities'
response to identical gopher disturbances. Percent cover of vegetation on mounds
increased 3 times faster in the pasture than the prairie; and vegetation on and off
mounds in the pasture was more alike (71% Similarity) than vegetation on and off
mounds in the prairie (50% Similarity).
Despite these differences, the relative contribution of each source of
colonization was strikingly similar in the two communities. Vegetative
encroachment and emergence contributed more to overall colonization rates (76%
in the pasture; 75% in the prairie) than did establishment from seeds or buried
root fragments. Emergence from underneath the mounds was favored by the
shallow depth of mounds, minimal alteration of the substrate associated with mound
building, and dominance of perennial species with erect growth forms. The small
area and high perimeter to surface area ratio resulted in a high percent
colonization from encroachment of surrounding vegetation. Colonization from the
rain and bank contributed less to mound closure and may have been limited by a
low abundance of propagules in those two sources.
Successful colonists differed in their patterns of colonization. Festuca rubra,
Agoseris heterophylla, Plantago lanceolata and Prune lla vulgaris colonized almost
exclusively via emergence. Fragaria virginiana colonized by the extension of stolons
both onto (encroachment) and up through mounds (emergence). Colonization from
the seed rain was important in many annual species, such as Ranunculus
occidentalis, Clarkia quadrivulnera, and Sherardia arvensis and the biennial species,
Hypericum perforatum. One annual species, Cynosurus echinatus colonized to
some degree from several modes of colonization. Mound disturbances had greater
forb and annual species cover in both communities than was represented in the
background vegetation, although the difference was much greater in the prairie.
Results of this and other studies of gopher disturbance suggest that the
relative abundance of perennials and annuals, evenness of species abundance and
competitive relationships can help to predict patterns of colonization and effects of
gopher mounds on community diversity.Graduation date: 1991
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Ellery, William Nolan. "Classification of vegetation of the South African grassland biome." Thesis, 1992. http://hdl.handle.net/10539/22708.
Full textAbstract:
A thesis submitted to the Faculty of Science,
University of the Witwatersrand, Johannesburg,
in fulfilment of the requirements for the degree
of Doctor of Philosophy.
Johannesburg 1992.The aim of the study was to develop understanding of the relationships between vegetation types of the grassland biome of South Africa and the environment, with an emphasis on structural and functional characteristics. The grassland biome in South Africa has traditionally been divided into 'pure' grasslands, assumed to be climatically determined, and 'false' grasslands of recent anthropogenic origin. A review of literature from several disciplines including palaeobotany, archaeology, ecology and biogeography indicates that this is not a valid distinction. It is clear that the distribution of the grassland biome as a whole is poorly understood, but the general correlation between the distribution of biomes and climate elsewhere in the world suggests that this warrants more detailed investigation. A water balance approach was used to develop climatic incices that both predict the distribution of grasslands, and are easy to interpret biologically. The indices are the mean. number of days per annum when moisture is available for plant growth, tbe mean temperature on days when moisture is available for plant growth (wet season temperature),. and the mean temperature when moisture is not available for plant growth (dry season temperature). Based on these three.indices the grassland biome in South Africa call be distinguished from neighbouring biomes. The fynbos and succulent karoo biomes have rainfall in winter. The grassland, nama-karoo and savanna biomes have' rainfall in summer. The forest biome experiences rainfall throughout the year. Of the summer rainfall biomes, the quantity of water available in the grassland biome b greater than in the nama-woo, similar to savanna, but less than forest. Grasslands experience cooler dry season temperatures than savannas. The localised distribution of woody plants within the. grassland biome suggests that it is the effect of climate on the fire regime that may be of overriding importance h'l determining the distribution of the biome as a whole. Woody elements are restricted to sites that are either protected from fire, or experience fires of lower intensity than sites that support- grassland, The unifying feature of the grassland biome is its proneness to fire. The presence of a warm, moist season promotes plant production and leads to a high standing crop close to the ground. The prolonged dry season causes vegetation to dry out annually, rendering it flammable. More arid biomes have plants more widely spaced, making it difficult for fire to spread. In more mesic biomes where rainfall is less sea.sonal than in the grasslands or savannas, fuels do not dry out sufficiently to ignite, A number of additional climatic features may promote burning in the grassland biome, It has the highest lightning density of all South Africa's biomes. 'tVarm, dry 'berg' winds desiccate fuels and 1 omote burning in the more mesic grasslands, The 'curing' of the grass sward due to dry season frost and temperature drop is important in establishing early dry season flammability. Savanna trees are fire tolerant, but they appear sensitive to the cold temperatures prevaient in the grassland biome in. the dry season, The relationship between the distribution of functional characters of grassland plants and environmental conditions was investigated. The distincrion between sweetveld, mixed veld and sourveld was recognised as one of the most Important functional features of South Africa's grasslands, The distribution of these vegetation types was examined in detail. Sweetveld occurs In warm, dry areas; sourveld in cool, moist areas. There Is overlap between these tyP.Js that Is dependant on soil nutrient status. Sweetveld that occurs in climatic conditions that would be expected to support mixed veld and sourveld, is on soils derived from basic parent material, including basalt, dolerite, gabbro and norite. Similarly, sourveld that occurs in areas that climatically would be expected to support sweetveld, is on soils derived from acid parent material such as sandstone and quartzite .. Soil nutrients that are most highly correlated to the occurrence of these three veld types are phosphoms availability and an index of nitrogen mineralization potential. 'l'here is an increase in bot; available phosphorus and the index of readily mineralizable nitrogen from sourveld to mixed veld to sweetveld. These features am inc01).10111tedinto a conceptual model that relates the distribution of these grassland types to carbon and nitrogen metabolism, with the role of phosphorus either similar to nitrogen, or else it may act indirectly by affecting the. rate of nitrogen mineralization, Nitrogen mineralization OCcursat lower water availability than carbon assimilation, and its temperature optimum is higher than that of carbon assimilation. Where nitrogen mineralization is favoured ielative to carbon assimilation, sweetveld is likely to (}C(.1\Xr. Where carbon assimilation is. favoured relative to; nitrogen mineralization, sourveld is likely to occur ....Soil texture affects the balance between these two processes in the degree to wm.r;h it protects soil organic matter, and thereforv the size of the nitrogen and ph_QSPllO_rOll.S pools. Changes in the rlj,stribution of South Africa's b~\omesfor a scenario of climate change are predicted using the biome model developed in this study. This illustrates the value of developing predictive models.
MT2017
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Wemheuer, Franziska. "Influence of Grassland Management and Herbivory on Diversity and Ecology of plant-associated Bacterial Communities." Doctoral thesis, 2013. http://hdl.handle.net/11858/00-1735-0000-0022-5FFE-F.
Full textAbstract:
In den vergangenen Jahren rückten Pflanzen-assoziierte Bakterien auf Grund ihrer Bedeutung für die Pflanzengesundheit und das ökologische Gleichgewicht zunehmend in den Fokus aktueller Forschungen. Trotz der stetig steigenden Zahl wissenschaftlicher Studien ist der Einfluss von Bewirtschaftungsmaßnahmen auf die Diversität dieser Bakteriengemeinschaften in Grünlandökosystemen ver-gleichsweise wenig untersucht. In dieser Studie haben wir neue und interessante Erkenntnisse über die Diversität von Pflanzen-assoziierten Bakterien in Grünlandökosystemen gewonnen.
Sämtliche Untersuchungen dieser Arbeit wurden auf der GrassMan-Fläche in den Mittelgebirgslagen des Solling in Deutschland durchgeführt. Das GrassMan-Experiment wurde 2008 in einer Matrix von Wiesenplots schachbrett-artig auf historisch altem Grünland errichtet. Die Bewirtschaftungsintensität unterschied sich bezüglich der Häufigkeiten (einmal jährlich im Juli oder dreimal jährlich im Mai, Juli und September) und der Düngung (keine Düngung bzw. Düngung mit NPK). Außerdem wurde durch gezielten Herbizid-Einsatz gegen Monokotylen oder gegen Dikotylen ein Gradient in der Anzahl der Pflanzenarten erzeugt.
Die Arbeit umfasst drei Hauptthemen. Erstens wurde der Einfluss verschiedener Bewirtschaftungsmaßnahmen auf die bakterielle Endophyten-gemeinschaft in den drei Grasarten Festuca rubra, Lolium perenne und Dactylis glomerata untersucht. Hierfür wurden im September 2010 und im April, Juli und September 2011 Pflanzenproben auf den Dikotylen-reduzierten Plots gesammelt. Die Umwelt-DNS wurde aus den Proben extrahiert und als Template für 16S PCRs eingesetzt. Die Struktur der bakteriellen Endophyten-Gemeinschaft wurde mittels DGGE-Analyse der erhaltenen PCR-Produkte untersucht.
Wir konnten Unterschiede der Endophyten-Gemeinschaftsstrukturen hinsichtlich der verschiedenen Bewirtschaftungsintensitäten feststellen. Während die Düngung einen starken Effekt auf die bakterielle endophytische Diversität sowohl in F. rubra als auch in L. perenne hatte, wurden die bakteriellen Endo-phyten in D. glomerata nicht dadurch beeinflusst. Die Proben von L. perenne, die von den ungedüngten Plots stammten, bildeten zudem eindeutige Gruppen bei der Analyse der DGGE-Banden bezüglich der zwei Schnitthäufigkeiten. Somit beeinflusste auch die Mahd die bakterielle Endophyten-Gemeinschaft in den Pflanzen. Weiterhin konnten wir einen starken saisonalen Effekt auf die Struktur der endophytischen Gemeinschaft nachweisen. Da saisonale Veränderungen und die Pflanzenart die Zusammensetzung der endophytischen Bakteriengemeinschaft beeinflussten, können sich die Auswirkungen unterschiedlicher Bewirtschaf-tungsintensitäten mit der Zeit und der untersuchten Pflanzenart verändern. Dieses Ergebnis sollte bei zukünftigen Studien berücksichtigt werden.
Das zweite Ziel dieser Arbeit war die Beantwortung der Frage, wie sich oberirdische Herbivorie auf die Bakteriengemeinschaft in der Rhizosphäre auswirkt. Hierfür wurde im Herbst 2010 ein Lysimeter-Experiment auf der GrassMan-Fläche errichtet. Nach einer zweiwöchigen Herbivorie durch Grashüpfer und Schnecken im Sommer 2011 wurden Bodenproben von jedem Lysimeter genommen. Um Einblicke in die Zusammensetzung der bakteriellen Gemeinschaft in der Rhizosphäre zu erhalten, wurde die Gesamt-DNS aus den Bodenproben extrahiert und als Template in 16S rDNS PCRs eingesetzt. Die Gemeinschaftsstruktur wurde mittels DGGE-Analyse bzw. Pyrosequenzierung der erhaltenen PCR Produkte untersucht. Die Herbivorie hatte keinen Einfluss auf die Anzahl der Bakterien (richness), während leichte Änderungen in der relativen Abundanz von einigen Bakteriengruppen festgestellt wurden. So war zum Beispiel die relative Abundanz einer unkultivierten Acidobacterium-Art in den Herbivorie-Lysimetern erhöht.
Bestandteil des Lysimeter-Experiments war zudem die Untersuchung des Einflusses der Pflanzenartenanzahl und der verschiedenen Bewirtschaftungs-maßnahmen auf die bakterielle Gemeinschaft in der Rhizosphäre. Der Einsatz von Herbiziden und eine niedrigere Schnittfrequenz reduzierten die Artenanzahl (richness) der Bakterien in der Rhizosphäre. Die Düngung hatte keinen Einfluss auf die Anzahl der Arten. Weitere Analysen zeigten, dass eine Vielzahl von verschiedenen bakteriellen Taxa in der Rhizosphäre durch die untersuchten Maßnahmen beeinflusst wurde. So war die Abundanz der Acidobacteria in den gedüngten Plots signifikant geringer. Das Gegenteil trat bei den Actinobacteria auf.
Abschließend lässt sich sagen, dass Pflanzen-assoziierte Bakterien sowohl in der Endosphäre und Rhizosphäre durch Bewirtschaftungsmaßnahmen beeinflusst werden. Die Untersuchung der Wirkung von verschiedenen Bewirtschaftungsintensitäten im Grünland und von oberirdischer Herbivorie auf Pflanzen-assoziierte Bakterien kann zu einem besseren Verständnis der multitrophischen Interaktionen zwischen Pflanzenart, Bakteriengemeinschaft und oberirdischen Herbivoren führen. Außerdem können uns die Ergebnisse dieser Arbeit helfen, die Effekte unterschiedlicher Bewirtschaftungsmaßnahmen auf Pflanzen-assoziierte Bakteriengemeinschaften und damit zusammenhängende Effekte auf das Bodenökosystem vorherzusagen.
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Phamphe, Avhafarei Ronald. "Phytosociology of Transkei grasslands." Diss., 2004. http://hdl.handle.net/2263/24809.
Full textAbstract:
A plant ecological study was conducted in the grasslands of Transkei to develop a better understanding of the distribution, structure and composition of the plant communities found in the area. The agricultural sector in developed and rapidly developing areas of southern Africa is faced with problems like veld deterioration and the loss of natural areas that effectively contribute to the depopulation of rural areas. The Grassland Biome Project was initiated to address the problem of increased destruction of natural resources because the most suitable area for agriculture falls within the grasslands of South Africa. The aim of the Grassland Biome Project is to integrate knowledge, comprehension and expertise, which will enable scientists to forecast the results of the available options of grassland management programs. Vegetation of Transkei forms part of this project. The study area (Transkei) borders on the kingdom of Lesotho in the north and Indian Ocean in the southeast. In the northeast it borders on KwaZulu-Natal and in the northwest, and in the west on the eastern Cape Province. Relevés were compiled in 379 random sample plots and four major plant communities, namely: Bush and Grassland vegetation of drier areas, Wet and Disturbed grassland, Grassland of Undulating Areas, and Moist Grasslands on Flat Plains, were found. The vegetation was classified by means of TWINSPAN and Braun-Blanquet procedures were found. The vegetation was classified by means of TWINSPAN and Braun-Blanquet procedures.Dissertation (MSc)--University of Pretoria, 2005.
Geography, Geoinformatics and Meteorology
Unrestricted
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Richardson, Matthew L. "Species composition and genetic structure of grassland plant communities and their influence on spiders and herbivorous insects /." 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3363074.
Full textAbstract:
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009.Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3281. Adviser: Lawrence M. Hanks. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.
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O'Connor, Timothy Gordon. "The influence of rainfall and grazing on the population and compositional response of some Savanna grasslands." Thesis, 1991. https://hdl.handle.net/10539/27836.
Full textAbstract:
A thesis submitted to the Faculty of Science,
University of the Witwatersrand, Johannesburg,
in fulfilment of the requirements for the degree
of Doctor of PhilosophyThe study aimed to differentiate the effect of rainfall and grazing on the compositional change of savanna grasslands, and to explain responses in terms of the life history patterns of the main species, An extinction prone perennial grass under heiry grazing was identified as a palatable, obligate seed reproducer with low seed production and poor dispersal (e.g. Themeda triandra and Reteropogon contortus), wnich could become extinct if the established population and the seed bank were eliminated. Aristrida species were expected to show the converse pattern. Grazing was manipulated for three or five years, and rainfall for one year, on a sandveld site, and two clay soil sites which supported the same species in different amounts, respectively. (Abbreviation abstract)
Andrew Chakane 2019
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Rothenwöhrer, Christoph. "Plant-herbivore-predator communities and grassland management intensity - Implications for biodiversity conservation practices on local and landscape scales." Doctoral thesis, 2012. http://hdl.handle.net/11858/00-1735-0000-000D-F18D-9.
Full text