Etudier un phénomène écologique requiert de le considérer dans sa globalité afin d’appréhender l’ensemble de ses causes et ses conséquences. Dans la plaine de la Crau, écosystème pseudo-steppique du sud est de la France, la fragmentation des habitats, la perte de biodiversité et les changements d’usage ont favorisé l’envahissement de fragments relictuels de steppe par Rubus ulmifolius Schott. Par une approche multiscalaire, les objectifs de cette thèse sont de mettre en évidence les facteurs responsables de cet envahissement, d’appréhender ses conséquences sur la communauté végétale et de tester d’éventuelles techniques de restauration écologique en évaluant leurs effets à l’échelle de la communauté et de la population de ronces. La présence de fortes proportions de zones irriguées et de parcelles anciennement cultivées dans la matrice paysagère proche des zones envahies correspond à des taux de recouvrements parcellaires en ronciers plus élevés. A l’échelle de la communauté végétale, les infiltrations hydriques ont également des effets importants sur la végétation steppique en permettant le développement d’une espèce herbacée compétitrice : Brachypodium phoenicoïdes (L.) Roem. & Schult. Aucun des différents régimes de perturbation (débroussaillage et/ou pâturage) testés, croisés au drainage ou non du sol ne permet de restaurer à court terme (trois années) l’intégrité de la steppe de référence. Seule une augmentation significative de la richesse et de la diversité spécifique est mesurée dans le cas d’un débroussaillage et d’un pâturage annuel des placettes. A l’échelle des ronces, les effets des différents traitements varient selon l’année, la saison ou la période de la journée considérée. Les régimes de perturbation (débroussaillage et/ou pâturage) ont cependant plus d'influence sur les traits éco-physiologiques et morphologiques de la ronce que la limitation des ressources en eau. Nos résultats soulignent ainsi la difficulté de contrôler à court terme la dynamique d’une espèce envahissante. Ils ouvrent également le débat sur les objectifs de conservation et/ou de restauration des parcelles qui peuvent alors être considérées comme des écosystèmes dégradés ou comme de « nouveaux écosystèmes » dont les potentiels patrimoniaux sont encore inconnus. / Studying an ecological phenomenon require to consider it in its entirety in order to apprehend all the causes and consequences. In the Plain of La Crau, a sub-steppic ecosystem in southeastern France, habitat fragmentation, loss of biodiversity and land-uses changes have fostered the encroachment by a species of brambles Rubus ulmifolius Schott of the original steppic patches. Using a multiscale analysis, the aims of the thesis are to highlight the main drivers, to assess the consequences on the plant community and to test restoration techniques by evaluating their effects on plant community and on bramble population. The presence of high proportions of irrigated habitats and formely fallows around invaded plots correspond to the largest cover rates of brambles. At community scale, water infiltrations have also a great impact on the steppe plant community by favoring the dynamic of an herbaceous competitor species: Brachypodium phoenicoïdes (L.) Roem. & Schult. Among the different disturbance regimes tested (scrub-clearing and / or grazing), crossed with the presence or the absence of sol draining, none could restore in the short-term (3 years), the integrity of the steppe reference. A significant increase in species richness and diversity was only measured for drained, scrub-cleared and annually grazed plots. At bramble population scale, the effects of the different treatments change depending on the year, the season and the time of the day. However, disturbance regimes (clearing and / or grazing) have more impact on eco-physiological and morphological traits of the bramble than the water resources limitation. Our results highlight the difficulty controlling short-term dynamics of an invasive species. They question the objectives of conservation and / or restoration of plots which can then be considered as degraded ecosystems or as "novel ecosystems" whose potential patrimonial values are still unknown.

<p>U&nbsp; radu&nbsp; je&nbsp; analiziran&nbsp; odgovor&nbsp; lokalnih&nbsp; populacija&nbsp; tekunice&nbsp; u&nbsp; Vojvodini&nbsp; na<br />promene&nbsp; uslova&nbsp; klime&nbsp; i&nbsp; kori&scaron;ćenja&nbsp; zemlji&scaron;ta.&nbsp; Odgovori&nbsp; populacija&nbsp; tekunice<br />(tipičnog&nbsp; predstavnika&nbsp; otvorenih&nbsp; stani&scaron;ta&nbsp; i&nbsp; idealnog&nbsp; model&nbsp; organizma)&nbsp; na<br />pomenute promene omogućiće razmatranje kako mere na regionalnom nivou: i)<br />mogu unaprediti za&scaron;titu i očuvanje tekunice ii) ublažiti efekti promene klime i<br />kori&scaron;ćenja&nbsp; zemlji&scaron;ta&nbsp; iii)&nbsp; mogu&nbsp; usaglasiti&nbsp; razvoj&nbsp; poljoprivrede&nbsp; sa&nbsp; očuvanjem<br />biodiverziteta travnatih ekosistema. Kako&nbsp; bi&nbsp; se&nbsp; odgovorilo&nbsp; na&nbsp; pitanja&nbsp; i&nbsp; postavljene&nbsp; hipoteze&nbsp; u&nbsp; radu&nbsp; sprovedeno&nbsp; je terensko&nbsp; istraživanje,&nbsp; kori&scaron;ćen&nbsp; standardni&nbsp; prostorni&nbsp; pristup&nbsp; i&nbsp; ekolo&scaron;ko modelovanje.&nbsp; Sve&nbsp; primenjene&nbsp; tehnike&nbsp; su&nbsp; komplementarne&nbsp; jedna&nbsp; drugoj&nbsp; u dobijanju&nbsp; odgovora&nbsp; na&nbsp; postavljena&nbsp; pitanja&nbsp; gde&nbsp; rezultati&nbsp; jedne&nbsp; analize predstavljaju&nbsp; ulazne&nbsp; podatke&nbsp; za&nbsp; drugu&nbsp; analizu.&nbsp; U&nbsp; tezi&nbsp; su&nbsp; kori&scaron;ćeni&nbsp;&nbsp; podaci dobijeni&nbsp; na&nbsp; osnovu&nbsp; terenskog&nbsp; mapiranja&nbsp; lokalnih&nbsp; populacija&nbsp; i&nbsp; podaci&nbsp; iz eksperimenta&nbsp; modelovanja&nbsp; kao&nbsp; i&nbsp; serija&nbsp; podataka&nbsp; dobijena&nbsp; cenzusom&nbsp; kolonija tekunica i terenskim uzorkovanjem zemlji&scaron;ta i vegetacije. Rasprostranjenje&nbsp; populacija&nbsp; oblikuju&nbsp; klimatski&nbsp; uslovi&nbsp; ali&nbsp; pored&nbsp; abiotičkih faktora&nbsp; uslovljavaju&nbsp; ih&nbsp; i&nbsp; biotički&nbsp; faktori&nbsp; i&nbsp; kretanje&nbsp; jedinki.&nbsp; Promena&nbsp; klime direktno&nbsp; utiče&nbsp; na&nbsp; distribuciju&nbsp; optimalnih&nbsp; uslova.&nbsp; Istraženo&nbsp; je&nbsp; u&nbsp; kojoj&nbsp; meri&nbsp; će doći&nbsp; do&nbsp; promene&nbsp; u&nbsp; distribuciji&nbsp; optimalnih&nbsp; uslova&nbsp; sredine&nbsp; za&nbsp; tekunicu. Potencijalna promena&nbsp; analizirana je&nbsp; uzimajući&nbsp; u obzir klimatski scenario Max Plank&nbsp; Instituta&nbsp; sa&nbsp; tri&nbsp; rcp&nbsp; projekcije&nbsp; i&nbsp; tri&nbsp; generisana&nbsp; prostorna&nbsp; scenarijadistribucije&nbsp; otvorenih&nbsp; travnatih&nbsp; stani&scaron;ta&nbsp; u&nbsp; Vojvodini.&nbsp; Sagledavanje&nbsp; mogućih efekata promene sredinskih uslova&nbsp; dalo je&nbsp; mogućnost da se ukaže na zone koja će&nbsp; biti&nbsp; ključne&nbsp; za&nbsp; očuvanje&nbsp; populacija&nbsp; tekunica&nbsp; i&nbsp; travnatih&nbsp; ekosistema&nbsp; u Vojvodini. Sledeće,&nbsp; s&nbsp; obzirom&nbsp; da&nbsp; disperzija&nbsp; jedinki,&nbsp; dostupnost&nbsp; resursa&nbsp; kao&nbsp; i&nbsp; delovanje lokalnih&nbsp; faktora&nbsp; ugrožavanja&nbsp; (barijere,&nbsp; menadžment&nbsp; stani&scaron;ta,&nbsp; varijabilnost sredinskih uslova, predatorstvo, poljoprivredne aktivnosti) oblikuju distribuciju populacija&nbsp; u&nbsp; prostoru,&nbsp; u&nbsp; radu&nbsp; je&nbsp; analiziran&nbsp; i&nbsp; uticaj&nbsp; promene&nbsp; ovih&nbsp; faktora&nbsp; na distribuciju populacija. Na području lokalnog slatino-stepskog koridora srednjeg Banata istražene su kompozicija biljnih vrsta, upravljanje na stani&scaron;tu, promena u kompoziciji okolnih poljoprivrednih kultura i dinamika populacije. Dobijene su informacije o efektima lokalnih uslova na prisustvo&nbsp; kolonija,&nbsp; veličinu kolonija i kondiciono stanje jedinki. Informacije dobijene u ovim poglavljima&nbsp; su kasnije kori&scaron;ćeni&nbsp; za&nbsp; formiranju&nbsp; seta&nbsp; kriterijuma&nbsp; radi&nbsp; karakterizacije&nbsp; svih&nbsp; mapiranih stani&scaron;ta u Vojvodini. Dalje,&nbsp; veliku&nbsp; ulogu&nbsp; u&nbsp; poljoprivrednom&nbsp; predelu&nbsp; imaju&nbsp; tranziciona&nbsp; stani&scaron;ta&nbsp; koja&nbsp; povezuju&nbsp; lokalne&nbsp; populacije.&nbsp; Identifikovanje&nbsp; koja&nbsp; tranziciona&nbsp; stani&scaron;ta&nbsp; koriste jedinke tekunice je ključno za očuvanje&nbsp; populacija i&nbsp; ublažavanje trena&nbsp; opadanja brojnosti. Na terenu su mapirani distribucioni obrasci lokalnih kolonija tekunice i istraženo je da li postoje razlike na lokalnom i predeonom&nbsp; nivou u distribuciji nastanjenih i napu&scaron;tenih stani&scaron;ta na području Vojvodine. U&nbsp; radu&nbsp; je&nbsp; dalje&nbsp; analizirana&nbsp; mapirana&nbsp; mreža&nbsp; stani&scaron;ta&nbsp; lokalnih&nbsp; populacija&nbsp; i pretpostavljano&nbsp; je&nbsp; da&nbsp; populacije&nbsp; funkcioni&scaron;u&nbsp; i&nbsp; održavaju&nbsp; se&nbsp; u&nbsp; okviru metapopulacione strukture. Sa druge strane, veličina i povr&scaron;ina koju zauzimaju potencijalne&nbsp; metapopulacione&nbsp; struktura&nbsp; mapirane&nbsp; mreže&nbsp; stani&scaron;ta&nbsp; koje&nbsp; se razlikuju&nbsp; u&nbsp; odnosu&nbsp; na&nbsp; okupiranost,&nbsp; kapacitet&nbsp; i&nbsp; povezanost&nbsp; nisu&nbsp; bile&nbsp; poznate. Kako&nbsp; bi&nbsp; se&nbsp; kvantifikovale&nbsp; potencijalne&nbsp; metapopulacione&nbsp; jedinice&nbsp; i&nbsp; utvrdila vijabilnost&nbsp; svake&nbsp; definisane&nbsp; pojedinačne&nbsp; metapopulacione&nbsp; mreže&nbsp; kori&scaron;ćen&nbsp; je metod ključnog fragmenta. Mapirane mreže evaluirane su iz perspektive samog taksona&nbsp; i&nbsp; testiran&nbsp; je&nbsp; potencijalni&nbsp; disperzioni&nbsp; kapacitet.&nbsp; Proverena&nbsp; je permeabilnost predeonog matriksa između mapiranih stani&scaron;ta i identifikovani su potencijalni koridori za jedinke. Ovakav pristup daje uvid&nbsp; u koji deo predela&nbsp; je značajno&nbsp; i&nbsp; neophodno&nbsp; ulagati&nbsp; ograničena&nbsp; sredstva&nbsp; za&nbsp; za&scaron;titu&nbsp; prirode&nbsp; unutar regiona Vojvodine. U&nbsp; tezi&nbsp; je&nbsp; na&nbsp; kraju&nbsp; ocenjen&nbsp; doprinos&nbsp; trenutne&nbsp; regionalne&nbsp; konzervacione&nbsp; prakse za&scaron;titi&nbsp; stani&scaron;ta&nbsp; tekunice,&nbsp; dat&nbsp; pregled&nbsp; slabih&nbsp; tačaka&nbsp; i&nbsp; predlog&nbsp; predeono adaptacionih mera koji će doprineti za&scaron;titi i očuvanju populacije tekunice kao i mozaika otvorenih travnatih stani&scaron;ta.</p> / <p>The study analyzes the&nbsp; European ground squirrel (EGS) population&nbsp; response to land use and climate change&nbsp; in Vojvodina. The response&nbsp; of the EGS population&nbsp; (typical&nbsp; species&nbsp; of&nbsp; open&nbsp; grassland&nbsp; habitats&nbsp; and&nbsp; the&nbsp; ideal&nbsp; model&nbsp; organism)&nbsp; to changes in&nbsp; environmental conditions in this region will enable consideration of following measures at&nbsp; the local and landscape level: i) effective protection and<br />conservation of the EGS and habitat it relay on; ii) climate change and land use mitigation&nbsp; and&nbsp; adaptation&nbsp; iii)&nbsp; how&nbsp; can&nbsp; we&nbsp; harmonize&nbsp; the&nbsp; development&nbsp; of agriculture and preserve&nbsp; the biodiversity of&nbsp; grassland ecosystem&nbsp; in agricultural settings. In order to answer the questions of this study, the field research was conducted, standard spatial approach and ecological modeling were employed. All applied techniques&nbsp; are&nbsp; complementary&nbsp; to&nbsp; one&nbsp; another&nbsp; in&nbsp; obtaining&nbsp; responses&nbsp; to&nbsp; the questions&nbsp; asked.&nbsp; The&nbsp; results&nbsp; of&nbsp; one&nbsp; analysis&nbsp; represent&nbsp; the&nbsp; input&nbsp; data&nbsp; for&nbsp; the following&nbsp; one.&nbsp; The&nbsp; data&nbsp; for&nbsp; the&nbsp; study&nbsp; were&nbsp; obtained:&nbsp; from&nbsp; EGS&nbsp; local populations&rsquo;&nbsp; field&nbsp; mapping,&nbsp; from&nbsp; the&nbsp; modeling&nbsp; experiment,&nbsp; the&nbsp; census campaigned and the field sampling of soil and vegetation. Distribution of populations, which in addition to abiotic factors are conditioned by biotic factors and movement of individuals were evaluated in the context of climate&nbsp; change.&nbsp; Climate&nbsp; change&nbsp; directly&nbsp; affects&nbsp; the&nbsp; distribution&nbsp; of&nbsp; optimalconditions.&nbsp; The&nbsp; potential&nbsp; changes&nbsp; in&nbsp; distribution&nbsp; of&nbsp; optimal&nbsp; environmental conditions for EGS were assessed by considering&nbsp; changes in abiotic factors and the&nbsp; availability&nbsp; of&nbsp; grasslands.&nbsp; The&nbsp; climate&nbsp; scenario&nbsp; obtained&nbsp; using&nbsp; a&nbsp; dynamic vegetation&nbsp; map&nbsp; with&nbsp; three&nbsp; rcp&nbsp; projections&nbsp; and&nbsp; three&nbsp; spatial&nbsp; scenarios&nbsp; for&nbsp; the distribution of open grasslands were used. The extrapolation of a suitable area obtained&nbsp; by&nbsp; presence&nbsp; only&nbsp; model&nbsp; Maxent&nbsp; gives&nbsp; the&nbsp; possibility&nbsp; to&nbsp; point&nbsp; to&nbsp; the zones&nbsp; that&nbsp; will&nbsp; be&nbsp; crucial&nbsp; for&nbsp; preserving&nbsp; the&nbsp; populations&nbsp; and&nbsp; grassland ecosystems in future. Dispersion&nbsp; of&nbsp; individuals,&nbsp; availability&nbsp; of&nbsp; resources&nbsp; and&nbsp; the&nbsp; operation&nbsp; of&nbsp; local threats (e. g. barriers, habitat management, variability of the central conditions, predation, agricultural activities) shape the distribution of&nbsp; populations in space and time. In the area of the local saline steppe corridor of the central Banat in Vojvodina&nbsp; i)&nbsp; the&nbsp; composition&nbsp; of&nbsp; plant&nbsp; species,&nbsp; ii)&nbsp; open&nbsp; grassland&nbsp; habitat management&nbsp; iii)&nbsp; changes&nbsp; in&nbsp; the&nbsp; composition&nbsp; of&nbsp; surrounding&nbsp; crops&nbsp; and&nbsp; iv) population&nbsp; dynamics&nbsp; of&nbsp; EGS&nbsp; have&nbsp; been&nbsp; investigated.&nbsp; The&nbsp; effects&nbsp; of&nbsp; local conditions on the presence, size of colonies and condition of the individuals&nbsp; of EGS were assessed. The&nbsp; information obtained in these chapters was later used to&nbsp; form&nbsp; a&nbsp; set&nbsp; of&nbsp; criteria&nbsp; for&nbsp; the&nbsp; characterization&nbsp; of&nbsp; all&nbsp; mapped&nbsp; habitats&nbsp; in Vojvodina. In the agricultural area, transitional habitats connect local populations of many species. Identifying&nbsp; transitional&nbsp; habitats&nbsp; which potentially&nbsp; can&nbsp; be used by focal species&nbsp; is&nbsp; key&nbsp; to&nbsp; protect&nbsp; and&nbsp; mitigate&nbsp; population&nbsp; decline.&nbsp; For&nbsp; this&nbsp; purpose distribution&nbsp; patterns&nbsp; of&nbsp; the&nbsp; colonies&nbsp; were&nbsp; mapped&nbsp; in&nbsp; the&nbsp; field.&nbsp; The haracteristics&nbsp; and&nbsp; differences&nbsp; among&nbsp; mapped&nbsp; patches&nbsp; at&nbsp; the&nbsp; local&nbsp; and&nbsp; sub landscape scale were detected and evaluated. Later in the study the network of&nbsp; mapped habitats patches was evaluated. It was assumed&nbsp; that&nbsp; mapped&nbsp; populations&nbsp; in&nbsp; Vojvodina&nbsp; function&nbsp; within&nbsp; several&nbsp;&nbsp; metapopulations networks. However, the size and area of potential meta-population networks&nbsp; are&nbsp; likely&nbsp; to&nbsp; differ&nbsp; in&nbsp; relation&nbsp; to&nbsp; occupancy,&nbsp; capacity&nbsp; and&nbsp; habitat connectivity. The knowledge of potential population units was&nbsp; scarce. In&nbsp; order to&nbsp; quantify&nbsp; the&nbsp; potential&nbsp; population&nbsp; units,&nbsp; to&nbsp; determine&nbsp; the&nbsp; viability&nbsp; and conservation&nbsp; priority&nbsp; of&nbsp; each&nbsp; defined&nbsp; habitat&nbsp; network&nbsp; the&nbsp; key&nbsp; patch&nbsp; approach was used. Mapped networks were evaluated from the perspective of the taxon itself&nbsp; and potential dispersed capacity was tested. The ermeability of the matrix area,&nbsp; connectivity&nbsp; of&nbsp; the&nbsp; mapped&nbsp; habitats&nbsp; and&nbsp; the&nbsp; distribution&nbsp; of&nbsp; potential corridors&nbsp; was&nbsp; verified.&nbsp; This&nbsp; approach&nbsp; gives an&nbsp; opportunity&nbsp; to&nbsp; assess to&nbsp; which part&nbsp; of&nbsp; the&nbsp; area&nbsp; and&nbsp; population&nbsp; it&nbsp; is&nbsp; necessary&nbsp; to&nbsp; invest&nbsp; limited&nbsp; resources&nbsp; for nature protection in&nbsp; Vojvodina.The contribution of&nbsp; current regional conservation practice to protection of EGS was evaluated,&nbsp; a brief overview of the weak points and the proposal of preciseadaptation&nbsp; measures&nbsp; that&nbsp; should&nbsp; be&nbsp; taken&nbsp; in&nbsp; Vojvodina&nbsp; are&nbsp; presented&nbsp; in&nbsp; final chapter. The results of this study&nbsp; propose the&nbsp; development of&nbsp; spatial adaption measures&nbsp; and&nbsp; conservation&nbsp; design&nbsp; that&nbsp; will&nbsp; contribute&nbsp; not&nbsp; only&nbsp; in&nbsp; preserving EGS and habitats it relay on&nbsp; but also other wild plant and animal species&nbsp; in this intensively used agricultural settings.</p>

Plants often occur aggregated into clusters and this spatial pattern is supposed to affect pollinator behaviour and pollen dispersal. Such pollinator reaction may influence reproductive success of zoogamous plant species both in terms of number of available mates and their genetic diversity (nearby growing plant individuals are also often closely related, especially in clonal plants). In the present thesis, I investigated the influence of plant spatial aggregation on pollinator behaviour and how this translates into pollen transfer. For that purpose, I carried three experiments. In the Experiment 1, I used potted plants placed into arrays and aggregated into four patches in order to track the pollen dispersal by means of a UV-dye pollen analogue. I manipulated distances between plants within clusters (dense × loose) and between clusters (near × far). I conducted this experiment for three plant species differing in their pollinator spectra. In the Experiment 2, I observed pollinator foraging sequences (sequences of visited plant individuals) under the same experimental design as for the first experiment, but I carried out this experiment for five plant species. In addition in one study species, Dianthus carthusianorum, I conducted the Experiment 3 to get better insight into pollination effectiveness...

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 &gt; 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.

Prairie dogs (Cynomys sp.) are considered keystone species and ecosystem engineers for their grazing and burrowing activities (summarized here as disturbances). As climate changes and its variability increases, the mechanisms underlying organisms' interactions with their habitat will likely shift. Understanding the mediating role of prairie dog disturbance on vegetation structure, and its interaction with environmental conditions through time, will increase knowledge on the risks and vulnerability of grasslands. Here, we compared how plant taxonomical diversity, functional diversity metrics, and community-weighted trait means (CWM) respond to prairie dog C. mexicanus disturbance across grassland types and seasons (dry and wet) in a priority conservation semiarid grassland of Northeast Mexico. Our findings suggest that functional metrics and CWM analyses responded to interactions between prairie dog disturbance, grassland type and season, whilst species diversity and cover measures were less sensitive to the role of prairie dog disturbance. We found weak evidence that prairie dog disturbance has a negative effect on vegetation structure, except for minimal effects on C4 and graminoid cover, but which depended mainly on season. Grassland type and season explained most of the effects on plant functional and taxonomic diversity as well as CWM traits. Furthermore, we found that leaf area as well as forb and annual cover increased during the wet season, independent of prairie dog disturbance. Our results provide evidence that grassland type and season have a stronger effect than prairie dog disturbance on the vegetation of this short-grass, water-restricted grassland ecosystem. We argue that focusing solely on disturbance and grazing effects is misleading, and attention is needed on the relationships between vegetation and environmental conditions which will be critical to understand semiarid grassland dynamics under future climate change conditions in the region.

Ziel der vorliegenden Forschungsarbeit ist es, eine Übersicht der Pflanzengesellschaften Sachsens vorzulegen. Dabei wird zunächst ein grundsätzliches syntaxonomisches Konzept zur Bearbeitung der Vegetation Sachsens vorgestellt. Inhalt des vorliegenden ersten Heftes ist die Klasse der Molinio-Arrhenatheretea (Kulturgrasland aus Fettwiesen und Fettweiden, jedoch ohne Kriech- und Flutrasen). Die Pflanzengesellschaften werden durch Referenztabellen und Texte in ihrer Vielfalt mit wichtigen regionalen und standörtlichen Ausprägungen in prägnanter Weise beschrieben. Grundlage sind ca. 3000 syntaxonomisch bearbeitete Vegetationsaufnahmen. Die Übersicht ist so strukturiert, dass sie sowohl mit der - bislang ausschließlich in Textform vorliegenden - Rote Liste der Pflanzengesellschaften Sachsens (BÖHNERT et al. 2021) als auch mit dem sächsischen Kartier- und Bewertungsschlüssel für FFH-Lebensraumtypen (LFULG 2009), dessen Erfassungskriterien wesentlich auf der Zuordnung zu Pflanzengesellschaften beruhen, verglichen werden kann. Bei der Formulierung der deutschen Namen der Syntaxa wurden die Vorschläge von KORNECK (1984) berücksichtigt, die auf den Ebenen von Assoziationen und Verbänden zu Veränderungen gegenüber BÖHNERT et al. (2021) führten. Die Übersicht soll den Kartierern des Langzeitmonitoring der FFH-Lebensraumtypen in Sachsen als informative Handreichung zum Kartier- und Bewertungsschlüssel zur Verfügung gestellt werden. Darüber hinaus wird ein breiter Nutzerkreis im Bereich Biologie und Naturschutz angesprochen. / The aim of the present research work is to present an overview of the plant communities in Saxony. Therefor a basic syntaxonomic concept for processing the vegetation of Saxony is presented. This issue also presents a reviewed classification of Molinio-Arrhenatheretea (without flood and creeping swards). The plant communities are described by reference tables and texts to show their diversity and important regional and local characteristics. The work is based on more than 3000 syntaxonomic relevés. The classification allows a comparison with the Red List of Plant Communities in Saxony (BÖHNERT et al. 2021) and with the Saxon mapping and assessment key for FFH habitat types (LfULG 2009). The results support the recognition and mapping of FFH-habitats. The publication adresses a wide range of users in the field of biology and nature conservation.

Soil organic matter (OM) is a complex mixture of compounds, mainly derived from plants and microbes at various states of decay. It is part of the global carbon cycle and is important for maintaining soil quality. OM protection is mainly attributed to its association with minerals. However, clay minerals preferentially sorb specific OM structures, and clay sorption sites become saturated as OM concentrations increase. Therefore, it is important to examine how OM structures influence their association with soil minerals, and to characterize other protection mechanisms. Several techniques, which provide complementary information, were combined to investigate OM composition: Biomarker (lignin phenol, cutin-OH acid, and lipid) analysis, using gas chromatography/mass spectrometry; solid-state 13C nuclear magnetic resonance (NMR) spectroscopy; and an emerging method, solution-state 1H NMR spectroscopy. OM composition of sand-, silt-, clay-size, and light fractions of Canadian soils were compared. It was found that microbial-derived and aliphatic structures accumulated in clay-size fractions, and lignin phenols in silt-size fractions may be protected from further oxidation. Therefore, OM protection through association with minerals may be structure-specific. OM in soils amended with maize leaves, stems, and roots from a biodegradation study were also examined. Over time, lignin phenol composition, and oxidation; and aliphatic structure contribution changed less in soils amended with leaves compared to soils amended with stems and roots. Compared to soils amended with leaves and stems, amendment with roots may have promoted the more efficient formation of microbial-derived OM. Therefore, plant chemistry influenced soil OM turnover. Synthetic OM-clay complexes and soil mineral fractions were used to investigate lignin protection from chemical oxidation. Coating with dodecanoic acid protected lignin from chemical oxidation, and overlying vegetation determined the relative resistance of lignin phenols in clay-size fractions from chemical oxidation. Therefore, additional protection from chemical oxidation may be attributed to OM composition and interactions between OM structures sorbed to clay minerals. Overall, these studies suggest that while association with minerals is important, OM turnover is also influenced by vegetation, and protection through association with clay minerals was modified by OM structure composition. As well, OM-OM interaction is a potential mechanism that protects soil OM from degradation.

No description available.

Soil organic matter (OM) is a complex mixture of compounds, mainly derived from plants and microbes at various states of decay. It is part of the global carbon cycle and is important for maintaining soil quality. OM protection is mainly attributed to its association with minerals. However, clay minerals preferentially sorb specific OM structures, and clay sorption sites become saturated as OM concentrations increase. Therefore, it is important to examine how OM structures influence their association with soil minerals, and to characterize other protection mechanisms. Several techniques, which provide complementary information, were combined to investigate OM composition: Biomarker (lignin phenol, cutin-OH acid, and lipid) analysis, using gas chromatography/mass spectrometry; solid-state 13C nuclear magnetic resonance (NMR) spectroscopy; and an emerging method, solution-state 1H NMR spectroscopy. OM composition of sand-, silt-, clay-size, and light fractions of Canadian soils were compared. It was found that microbial-derived and aliphatic structures accumulated in clay-size fractions, and lignin phenols in silt-size fractions may be protected from further oxidation. Therefore, OM protection through association with minerals may be structure-specific. OM in soils amended with maize leaves, stems, and roots from a biodegradation study were also examined. Over time, lignin phenol composition, and oxidation; and aliphatic structure contribution changed less in soils amended with leaves compared to soils amended with stems and roots. Compared to soils amended with leaves and stems, amendment with roots may have promoted the more efficient formation of microbial-derived OM. Therefore, plant chemistry influenced soil OM turnover. Synthetic OM-clay complexes and soil mineral fractions were used to investigate lignin protection from chemical oxidation. Coating with dodecanoic acid protected lignin from chemical oxidation, and overlying vegetation determined the relative resistance of lignin phenols in clay-size fractions from chemical oxidation. Therefore, additional protection from chemical oxidation may be attributed to OM composition and interactions between OM structures sorbed to clay minerals. Overall, these studies suggest that while association with minerals is important, OM turnover is also influenced by vegetation, and protection through association with clay minerals was modified by OM structure composition. As well, OM-OM interaction is a potential mechanism that protects soil OM from degradation.

The world-wide intensification of agriculture has led to a decline in species richness due to land use change, isolation, and fragmentation of natural and semi-natural habitats in agricultural and forestry landscapes. As a consequence, there is a current landscape management focus on the importance of green infrastructure to mitigate biodiversity decline and preserve ecosystem functions e.g. pollination services and pest control. Even though intensification in agriculture has been ongoing for several hundreds of years, remnant habitats from earlier management practices may still be remaining with a surprisingly high plant richness. Preserving these habitats could help conserving plant species richness in agricultural landscapes, as well as other organisms that are dependent on plants for food and shelter. In this thesis I focus on two small remnant habitats; midfield islets and borders between managed forest and crop field in southeastern Sweden. In the past, both habitats were included in the grazing system and therefore often still have remnant population of grassland specialist species left today. I have used these two remnant habitats as model habitats to investigate the effect of landscape factors and local factors on species richness of plants, flower morphologies and plants with fleshy fruits. Additively, I analysed the effect of surrounding landscape and local openness on the functions; pollination success, biological pest control of aphids and seed predation on midfield islets. One of my studies showed that spatial distribution and size of the habitat affected plant species richness. Larger habitat size and higher connectivity between habitats increased species richness of plants in the habitats. Openness of the habitats was shown to be an important factor to increase species richness and richness of flower morphologies, both on midfield islets and in forest borders. Even though midfield islets had the highest species and morphology richness, both habitat types are needed for habitat complementary as forest borders have more plants with fleshy fruits and a higher richness of plant species that flowers in spring/early summer. It was also shown that a more complex forest border, not just with gaps in the canopy, but also with high variation in tree stem sizes increases plant species richness in the field layer. The conclusion is that by managing small remnant habitats to remain or become more semi-open and complex in their structure, would increase species richness of plants, grassland specialist species, and flower morphologies. It would also increase some ecosystem functions as seed predation and biologic pest control of aphids are more effective close to trees. If both midfield islets and forest borders would be managed to be semi-open, the area and connectivity of semi-open habitat would increase in the agricultural landscape, which may also improve pollination success as the connectivity between populations has a possibility to increase. Grassland specialist species are clearly abundant in the small remnant habitats. As the decline of semi-natural grasslands is causing a decline in grassland specialists’ species, not only plants, I recommend that small remnant habitats are included in conservation and management plans and strategies to improve habitat availability and connectivity for grassland species in agricultural landscapes. / <p>Research funder Ekoklim. Project:4339602.</p><p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.</p>