Changes to vegetation architecture within a natural habitat can have profound impacts upon ecological community function, but the relative influence of vegetation architecture itself and potential indirect influences of associated food resources are often difficult to disentangle. I present the results of a three-year study designed to address the community level impacts of changes in big sagebrush (Artemisia tridentata) architecture and associated prey availability upon the ground-dwelling arthropod community. Three experimental sagebrush architecture treatments (low, intermediate, and high foliage density) and two levels of prey insect availability treatment (natural and baited/increased prey availability) were imposed in a sage-steppe ecosystem. The ground-dwelling spider (top predators) and insect (prey) response to all combinations of the six treatments were assessed through abundances in pitfall traps. Chapter 2 demonstrates that changes in a single shrub’s architecture did not markedly impact prey arthropod availability on the ground, though an overall increase in arthropod abundance was detected within baited shrubs. This indicates changes to vegetation architecture do not impact prey insect availability for ground-dwelling spiders. Thus, changes in shrub architecture and not the associated prey base directly alter the ground-dwelling spider community. Chapter 3 shows that architectural manipulation of a single sagebrush directly influences the ability of certain ground-dwelling spider guilds to persist beneath the shrub. Data within Chapters 2 and 3 support the conclusion that vegetation architecture directly affects ground-dwelling spider community structure and composition. Finally, Chapter 4 explores how the relative impacts of vegetation architecture and prey availability upon ecological communities can shift depending upon the spatial context in which the manipulations take place, given the differences in mobility of species within the grounddwelling spider and insect prey communities. Within this study, Diurnal and Nocturnal Wanderers responded to manipulations in prey availability at a larger spatial context (patches of 15 shrubs) while more stationary Trappers and Ambushers did not. Through simultaneous manipulation of vegetation architecture (Artemisia tridentata, big sagebrush) and associated insect prey base in different spatial contexts, this dissertation demonstrates that vegetation architecture directly affects ground-dwelling spider community organization at the species and guild levels of diversity. Shifts in spider (predator) functional diversity can ultimately impact arthropod decomposer and herbivore populations, influencing fundamental ecosystem processes such as decomposition and productivity.

In recent years, the importance of sagebrush to shrub-steppe ecosystems and associated plant and animal species has been recognized. The historical removal of herbaceous species by excessive and uncontrolled livestock grazing on many of our sagebrush ecosystems has resulted in a stagnant state where dense, competitive stands of sagebrush prevent herbaceous species from recovering. Most early research on sagebrush control was directed toward eradication to increase herbaceous forage for livestock production, rather than sagebrush thinning to improve shrub vigor and understory production for wildlife habitat and community diversity. Mechanical treatments have the ability to retain shrub and herbaceous components, while improving diversity within degraded sagebrush communities. This study evaluated the effects of 6 mechanical treatments and revegetation of a Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) community in northern Utah that were treated in the fall of 2001 and spring of 2002 (aerator only). Disking and imprinting killed 98% of the sagebrush and significantly (p < 0.05) lowered cover and density of sagebrush more than any other treatment. Disking and imprinting was the only mechanical treatment to reduce cover and density of residual understory species, but also to successfully establish seeded grasses. One-way Ely chaining, 1-way and 2-way pipe harrowing, and aerating in the fall and spring reduced sagebrush cover from greater than 20% to less than 5% and reduced density by about half. Two years after mechanical treatment surviving sagebrush had greater leader and seed stalk growth than untreated sagebrush. Choice of a mechanical treatment to increase and diversify the perennial herbaceous component and retain the shrub component of sagebrush communities depends on the amount of residual herbaceous species, as well as economics. Chaining is potentially most economical for diversifying communities with a residual herbaceous perennial component. It is uncertain whether successful revegetation from disking and imprinting was a result of significant reduction in sagebrush, residual perennial herbaceous species, or both. Response of sagebrush communities with a very limited perennial herbaceous understory needs to be tested to determine how much and what kind of mechanical reduction in sagebrush is needed for successful revegetation.

No description available.

Inner Mongolian grasslands are part of the vast Eurasian steppe belt and were used for nomadic pastoralism for thousands of years. As a result of political and economic changes in China in the last century, this mobile grazing management has been replaced by a sedentary and intensified livestock production. Stocking rates have increased substantially, overshooting the carrying capacity of the grasslands. These land use changes have induced severe grassland degradation. The impact and causes of grassland degradation have been investigated by the Sino-German joint research group MAGIM (Matter fluxes in grasslands of Inner Mongolia as influenced by stocking rate) in the Xilin River catchment of Inner Mongolia since 2004. This work is part of subproject P6, which amongst others pursues the goal of quantifying water balance exchange by micrometeorology and remote sensing. The dominating process of water balance losses in Inner Mongolian grasslands is evapotranspiration (ET), whereby water vapour is released into the lower atmosphere. ET is highly variable in both time and space in this semi-arid environment, as it is coupled with the typically fluctuating amount of precipitation (P). However, despite ET being the key output process of the hydrological cycle of Inner Mongolian grasslands and despite its important role as an indicator for ecosystem functioning, little is known about its spatiotemporal distribution and variability in this remote area. Recent studies on ET have demonstrated variations due to phenology, soil moisture and land use, but these studies have been limited to short periods and have been conducted on a few field sites in close proximity with debatable representativeness for the 2600 km² of grasslands in the Xilin River catchment. The development of a number of remote sensing methods in the last decades has introduced various approaches to determining spatial ET from space, but the application of remotely sensed ET in regional long-term studies is still problematic. Nevertheless, a variety of surface parameters are provided by the sensor MODIS (moderate resolution imaging spectroradiometer) at a resolution of approx. 1km. The aim of this work was (1) to close the gap between the limitations of available local ET measurements and the need for long-term studies on spatial ET in Inner Mongolian grasslands and (2) to analyse the spatiotemporal variability of ET and its implications on livestock management in this area. Therefore, micrometeorological data, remote sensing products and hydrological modelling with BROOK90 were integrated to model spatial ET for the grasslands of the Xilin River catchment over 10 years. The hydrological model BROOK90 calculates ET based on a modified Penman-Monteith approach including the separation of energy into transpiration and soil evaporation. The spatial application of the model was based on a land use classification restricted to the land use unit typical steppe. BROOK90 was parameterised from eddy covariance measurements, soil characteristics and MODIS leaf area index (LAI). Location and canopy parameters were provided individually, as well as the essential daily model input, including P and air temperatures for each pixel. Minimum and maximum air temperatures were calculated based on a relationship between measured air temperatures and MODIS surface temperatures (R²=0.92 and R²=0.87, n=81). Spatial P was estimated from a relationship found between the measured cumulative P of six rain gauges within the grasslands and the increase of MODIS LAI around these measurements (R²=0.80, n=270). Modelled ET is plausible and fits in the range of published results. ET was demonstrated to be highly variable in both time and space: the high spatiotemporal variability of eight-day ET is reflected by the coefficients of variation, which varied between 25% and 40% for the whole study area and were up to 75% for individual pixels. Soil evaporation reacts considerably more sensitively to precipitation pulses than transpiration. Modelled annual ET sums approached or exceeded precipitation sums in general; however, P exceeded ET in 2003, when exceptionally high precipitation occurred. The strong dynamics and the high spatiotemporal variability of ET clearly demonstrate that the current static livestock management is not adapted to the conditions of Inner Mongolian grasslands. New concepts for a sustainable livestock management could be developed in consideration of the intrinsic long-term patterns of spatial ET distribution and spatiotemporal variability identified in this work. Moreover, as this method for modelling spatial ET is not restricted to the grasslands of the Xilin River catchment, livestock management in other semi-arid grasslands could benefit from it as well. / Die Grasländer der Inneren Mongolei sind Teil des riesigen eurasischen Steppengürtels und wurden seit Tausenden von Jahren für die nomadische Weidewirtschaft genutzt. Als Folge der politischen und wirtschaftlichen Veränderungen in China im letzten Jahrhundert ist diese mobile Weidewirtschaft durch eine ortsgebundene und intensivierte Tierhaltung ersetzt worden. Besatzdichten wurden erheblich erhöht und die Tragfähigkeit der Grasländer wurde deutlich überschritten. Diese Landnutzungsänderungen haben schwerwiegende Degradationserscheinungen der Grasländer induziert. Die Ursachen und Auswirkungen der Degradation sind von der Deutsch-Chinesischen-Forschungsgruppe MAGIM (Matter fluxes in grasslands of Inner Mongolia as influenced by stocking rate) im Einzugsgebiet des Xilin-Flusses in der Inneren Mongolei seit 2004 untersucht worden. Diese Arbeit wurde im Rahmen des Teilprojektes P6 erstellt, welches unter anderem das Ziel verfolgt, Wasserhaushaltsprozesse mit Mikrometeorologie und Fernerkundung zu quantifizieren. Der dominierende Prozess der Wasserbilanz-Verluste in den Grasländern der Inneren Mongolei ist die Verdunstung (ET), wobei Wasserdampf in die untere Atmosphäre freigesetzt wird. ET ist in diesem semi-ariden Ökosystem in Zeit und Raum sehr variabel, da an die in der Regel schwankenden Niederschläge (P) gekoppelt. Trotz der Schlüsselrolle, die ET im Wasserkreislauf der Inneren Mongolei einnimmt, und der wichtigen Rolle als Indikator für die Funktionsweise des Ökosystems, ist wenig über die raum-zeitliche Verteilung und Variabilität von ET in dieser abgelegenen Region bekannt. Neuere Studien haben ET-Schwankungen aufgrund von Phänologie, Bodenfeuchte und Bodennutzung dargestellt, aber diese Studien sind auf kurze Zeiträume beschränkt und wurden auf nur wenigen Standorten, die sich in unmittelbarer Nähe befinden, durchgeführt. Dies stellt ihre Repräsentativität für die 2600 km² an Grasland im Xilin-Einzugsgebiet in Frage. Die Entwicklung von Fernerkundungsmethoden in den letzten Jahrzehnten hat verschiedene Ansätze zur Bestimmung der räumlichen ET hervorgebracht, jedoch ist die Anwendung von ET aus Fernerkundungsdaten in regionalen Langzeitstudien immer noch problematisch. Dennoch werden eine Vielzahl von Oberflächenparametern durch den Sensor MODIS (Moderate Resolution Imaging Spectroradiometer) bei einer Auflösung von ca. 1km zur Verfügung gestellt. Das Ziel dieser Arbeit war (1) die Lücke zwischen den verfügbaren lokalen ET-Messungen und dem Bedarf an langfristigen Untersuchungen zu räumlicher ET im Grasland der Inneren Mongolei zu schließen und (2) die räumlich-zeitliche Variabilität von ET vor dem Hintergrund des Beweidungsmanagements zu analysieren. Daher wurden mikrometeorologische Daten, Fernerkundungsprodukte und hydrologische Modellierungen mit BROOK90 integriert, um die räumliche ET für die Grasländer des Xilin-Einzugsgebietes über 10 Jahre zu modellieren. Das hydrologische Modell BROOK90 berechnet ET auf Basis eines modifizierten Penman-Monteith-Ansatzes einschließlich der Aufteilung in Transpiration und Bodenverdunstung. Die räumliche Anwendung des Standortmodells basiert auf einer Landnutzungsklassifikation und wurde für die Landnutzungsklasse typical steppe durchgeführt. Eddy-Kovarianz-Messungen, Bodeneigenschaften und MODIS-Blattflächenindex (LAI) wurden zur Parametrisierung von BROOK90 verwendet. Sowohl Lage- und Pflanzenparameter, als auch die notwendigen Modelleingangsdaten (Tageswerte von P und Lufttemperaturen), wurden für jeden Pixel individuell zur Verfügung gestellt. Minimum- und Maximum-Lufttemperaturen wurden mittels einer Beziehung zwischen gemessenen Lufttemperaturen und MODIS-Oberflächentemperaturen berechnet (R²=0.92 und R²=0.87, n=81). Räumliche P wurden aus einem Zusammenhang zwischen gemessenen kumulierten P von sechs Niederschlagsmessern im Untersuchungsgebiet und der Erhöhung des MODIS-LAI im Bereich dieser Messungen abgeleitet (R²=0.80, n=270). Die modellierte räumliche ET ist plausibel und liegt im Wertebereich der publizierten Ergebnisse. Es wurde gezeigt, das ET sehr variabel in Raum und Zeit ist: die raum-zeitlichen Schwankungen der achttägigen ET wurden durch den Variationskoeffizienten dargestellt, welcher zwischen 25% und 40% für das gesamte Untersuchungsgebiet variiert und für einzelne Pixel bis auf 75% ansteigt. Die Bodenverdunstung reagiert wesentlich empfindlicher auf Niederschlagsereignisse als die Transpiration. Modellierte Jahres-ET-Summen erreichen oder überschritten die Niederschlagssummen in der Regel, jedoch übertraf P die ET im Jahre 2003, als außergewöhnlich hohe Niederschläge aufgetreten sind. Die starke Dynamik und die hohe raum-zeitliche Variabilität der ET zeigen deutlich, dass die aktuelle statische Tierhaltung nicht an die Bedingungen in den Innermongolischen Grasländern angepasst ist. Neue Konzepte für eine nachhaltige Viehwirtschaft könnten unter Berücksichtigung der inhärenten langfristigen Muster der räumlichen Verteilung von ET und ihrer raum-zeitlichen Variabilität, die in dieser Arbeit identifiziert wurden, entwickelt werden. Außerdem ist die Anwendung der entwickelten Methode für die Modellierung räumlicher ET nicht auf die Grasländer des Xilin-Einzugsgebietes beschränkt; die Weidewirtschaft in anderen semi-ariden Grasländern könnte ebenfalls davon profitieren.

Inner Mongolian grasslands are part of the vast Eurasian steppe belt and were used for nomadic pastoralism for thousands of years. As a result of political and economic changes in China in the last century, this mobile grazing management has been replaced by a sedentary and intensified livestock production. Stocking rates have increased substantially, overshooting the carrying capacity of the grasslands. These land use changes have induced severe grassland degradation. The impact and causes of grassland degradation have been investigated by the Sino-German joint research group MAGIM (Matter fluxes in grasslands of Inner Mongolia as influenced by stocking rate) in the Xilin River catchment of Inner Mongolia since 2004. This work is part of subproject P6, which amongst others pursues the goal of quantifying water balance exchange by micrometeorology and remote sensing. The dominating process of water balance losses in Inner Mongolian grasslands is evapotranspiration (ET), whereby water vapour is released into the lower atmosphere. ET is highly variable in both time and space in this semi-arid environment, as it is coupled with the typically fluctuating amount of precipitation (P). However, despite ET being the key output process of the hydrological cycle of Inner Mongolian grasslands and despite its important role as an indicator for ecosystem functioning, little is known about its spatiotemporal distribution and variability in this remote area. Recent studies on ET have demonstrated variations due to phenology, soil moisture and land use, but these studies have been limited to short periods and have been conducted on a few field sites in close proximity with debatable representativeness for the 2600 km² of grasslands in the Xilin River catchment. The development of a number of remote sensing methods in the last decades has introduced various approaches to determining spatial ET from space, but the application of remotely sensed ET in regional long-term studies is still problematic. Nevertheless, a variety of surface parameters are provided by the sensor MODIS (moderate resolution imaging spectroradiometer) at a resolution of approx. 1km. The aim of this work was (1) to close the gap between the limitations of available local ET measurements and the need for long-term studies on spatial ET in Inner Mongolian grasslands and (2) to analyse the spatiotemporal variability of ET and its implications on livestock management in this area. Therefore, micrometeorological data, remote sensing products and hydrological modelling with BROOK90 were integrated to model spatial ET for the grasslands of the Xilin River catchment over 10 years. The hydrological model BROOK90 calculates ET based on a modified Penman-Monteith approach including the separation of energy into transpiration and soil evaporation. The spatial application of the model was based on a land use classification restricted to the land use unit typical steppe. BROOK90 was parameterised from eddy covariance measurements, soil characteristics and MODIS leaf area index (LAI). Location and canopy parameters were provided individually, as well as the essential daily model input, including P and air temperatures for each pixel. Minimum and maximum air temperatures were calculated based on a relationship between measured air temperatures and MODIS surface temperatures (R²=0.92 and R²=0.87, n=81). Spatial P was estimated from a relationship found between the measured cumulative P of six rain gauges within the grasslands and the increase of MODIS LAI around these measurements (R²=0.80, n=270). Modelled ET is plausible and fits in the range of published results. ET was demonstrated to be highly variable in both time and space: the high spatiotemporal variability of eight-day ET is reflected by the coefficients of variation, which varied between 25% and 40% for the whole study area and were up to 75% for individual pixels. Soil evaporation reacts considerably more sensitively to precipitation pulses than transpiration. Modelled annual ET sums approached or exceeded precipitation sums in general; however, P exceeded ET in 2003, when exceptionally high precipitation occurred. The strong dynamics and the high spatiotemporal variability of ET clearly demonstrate that the current static livestock management is not adapted to the conditions of Inner Mongolian grasslands. New concepts for a sustainable livestock management could be developed in consideration of the intrinsic long-term patterns of spatial ET distribution and spatiotemporal variability identified in this work. Moreover, as this method for modelling spatial ET is not restricted to the grasslands of the Xilin River catchment, livestock management in other semi-arid grasslands could benefit from it as well. / Die Grasländer der Inneren Mongolei sind Teil des riesigen eurasischen Steppengürtels und wurden seit Tausenden von Jahren für die nomadische Weidewirtschaft genutzt. Als Folge der politischen und wirtschaftlichen Veränderungen in China im letzten Jahrhundert ist diese mobile Weidewirtschaft durch eine ortsgebundene und intensivierte Tierhaltung ersetzt worden. Besatzdichten wurden erheblich erhöht und die Tragfähigkeit der Grasländer wurde deutlich überschritten. Diese Landnutzungsänderungen haben schwerwiegende Degradationserscheinungen der Grasländer induziert. Die Ursachen und Auswirkungen der Degradation sind von der Deutsch-Chinesischen-Forschungsgruppe MAGIM (Matter fluxes in grasslands of Inner Mongolia as influenced by stocking rate) im Einzugsgebiet des Xilin-Flusses in der Inneren Mongolei seit 2004 untersucht worden. Diese Arbeit wurde im Rahmen des Teilprojektes P6 erstellt, welches unter anderem das Ziel verfolgt, Wasserhaushaltsprozesse mit Mikrometeorologie und Fernerkundung zu quantifizieren. Der dominierende Prozess der Wasserbilanz-Verluste in den Grasländern der Inneren Mongolei ist die Verdunstung (ET), wobei Wasserdampf in die untere Atmosphäre freigesetzt wird. ET ist in diesem semi-ariden Ökosystem in Zeit und Raum sehr variabel, da an die in der Regel schwankenden Niederschläge (P) gekoppelt. Trotz der Schlüsselrolle, die ET im Wasserkreislauf der Inneren Mongolei einnimmt, und der wichtigen Rolle als Indikator für die Funktionsweise des Ökosystems, ist wenig über die raum-zeitliche Verteilung und Variabilität von ET in dieser abgelegenen Region bekannt. Neuere Studien haben ET-Schwankungen aufgrund von Phänologie, Bodenfeuchte und Bodennutzung dargestellt, aber diese Studien sind auf kurze Zeiträume beschränkt und wurden auf nur wenigen Standorten, die sich in unmittelbarer Nähe befinden, durchgeführt. Dies stellt ihre Repräsentativität für die 2600 km² an Grasland im Xilin-Einzugsgebiet in Frage. Die Entwicklung von Fernerkundungsmethoden in den letzten Jahrzehnten hat verschiedene Ansätze zur Bestimmung der räumlichen ET hervorgebracht, jedoch ist die Anwendung von ET aus Fernerkundungsdaten in regionalen Langzeitstudien immer noch problematisch. Dennoch werden eine Vielzahl von Oberflächenparametern durch den Sensor MODIS (Moderate Resolution Imaging Spectroradiometer) bei einer Auflösung von ca. 1km zur Verfügung gestellt. Das Ziel dieser Arbeit war (1) die Lücke zwischen den verfügbaren lokalen ET-Messungen und dem Bedarf an langfristigen Untersuchungen zu räumlicher ET im Grasland der Inneren Mongolei zu schließen und (2) die räumlich-zeitliche Variabilität von ET vor dem Hintergrund des Beweidungsmanagements zu analysieren. Daher wurden mikrometeorologische Daten, Fernerkundungsprodukte und hydrologische Modellierungen mit BROOK90 integriert, um die räumliche ET für die Grasländer des Xilin-Einzugsgebietes über 10 Jahre zu modellieren. Das hydrologische Modell BROOK90 berechnet ET auf Basis eines modifizierten Penman-Monteith-Ansatzes einschließlich der Aufteilung in Transpiration und Bodenverdunstung. Die räumliche Anwendung des Standortmodells basiert auf einer Landnutzungsklassifikation und wurde für die Landnutzungsklasse typical steppe durchgeführt. Eddy-Kovarianz-Messungen, Bodeneigenschaften und MODIS-Blattflächenindex (LAI) wurden zur Parametrisierung von BROOK90 verwendet. Sowohl Lage- und Pflanzenparameter, als auch die notwendigen Modelleingangsdaten (Tageswerte von P und Lufttemperaturen), wurden für jeden Pixel individuell zur Verfügung gestellt. Minimum- und Maximum-Lufttemperaturen wurden mittels einer Beziehung zwischen gemessenen Lufttemperaturen und MODIS-Oberflächentemperaturen berechnet (R²=0.92 und R²=0.87, n=81). Räumliche P wurden aus einem Zusammenhang zwischen gemessenen kumulierten P von sechs Niederschlagsmessern im Untersuchungsgebiet und der Erhöhung des MODIS-LAI im Bereich dieser Messungen abgeleitet (R²=0.80, n=270). Die modellierte räumliche ET ist plausibel und liegt im Wertebereich der publizierten Ergebnisse. Es wurde gezeigt, das ET sehr variabel in Raum und Zeit ist: die raum-zeitlichen Schwankungen der achttägigen ET wurden durch den Variationskoeffizienten dargestellt, welcher zwischen 25% und 40% für das gesamte Untersuchungsgebiet variiert und für einzelne Pixel bis auf 75% ansteigt. Die Bodenverdunstung reagiert wesentlich empfindlicher auf Niederschlagsereignisse als die Transpiration. Modellierte Jahres-ET-Summen erreichen oder überschritten die Niederschlagssummen in der Regel, jedoch übertraf P die ET im Jahre 2003, als außergewöhnlich hohe Niederschläge aufgetreten sind. Die starke Dynamik und die hohe raum-zeitliche Variabilität der ET zeigen deutlich, dass die aktuelle statische Tierhaltung nicht an die Bedingungen in den Innermongolischen Grasländern angepasst ist. Neue Konzepte für eine nachhaltige Viehwirtschaft könnten unter Berücksichtigung der inhärenten langfristigen Muster der räumlichen Verteilung von ET und ihrer raum-zeitlichen Variabilität, die in dieser Arbeit identifiziert wurden, entwickelt werden. Außerdem ist die Anwendung der entwickelten Methode für die Modellierung räumlicher ET nicht auf die Grasländer des Xilin-Einzugsgebietes beschränkt; die Weidewirtschaft in anderen semi-ariden Grasländern könnte ebenfalls davon profitieren.

Il y a deux millions d’années, les ancêtres d’Homo sapiens ont consommé de façon plus soutenue des protéines d’origine animale, ce qui leur a permis d’intégrer la guilde des carnivores, et ainsi marquer durablement le cours de leur histoire évolutive. L'ancienneté du phénomène étant associée à des limites matérielles, le contexte de la dispersion humaine dans l’ouest de la steppe à mammouth européenne, ainsi que la disponibilité des preuves archéologiques qui lui sont reliées, offre une occasion unique de se pencher sur cette étape importante de l’évolution des membres de la guilde des carnivores et des humains. La dispersion humaine, en tant qu’invasions biologiques, semble avoir mené à des impacts de nature maligne avec des conséquences qui ont affecté la diversité trophique, la compétition et les comportements des membres de la guilde, à la période culturelle associée au techno-complexe gravettien. Les méthodes d’analyses isotopiques ont aussi permis de mettre en lumière des informations permettant de participer à une meilleure compréhension du processus de transition Paléolithique moyen et supérieur et de mesurer l’influence des relations coévolutives intraguildes qui ont pu mener aux processus de domestication. / Two million years ago, the ancestors of Homo sapiens have increased their protein animal consumption, what it allowed them to join the guild of carnivores, and shaping a lasting way their evolution history. The antiquity of the phenomenon being associated with material limits, the context of human dispersal in the western European mammoth steppe, and the availability of archaeological evidence related to it, offers a unique opportunity to examine the evolution of carnivore guild members and humans. Human dispersal, as biological invasions, appears to have led to the impacts of a malignant nature with consequences that affected trophic diversity, competition, and behaviours of guild members, in the cultural period associated with the techno-complex Gravettian. The isotopic analysis methods have also used to highlight information allowing a better understanding of the Middle and Upper Palaeolithic transition process and to estimate the influence of intraguild coevolutionary relations which may have led to the domestication process.

L’étude de la composition isotopique de l’oxygène de l’émail des dents de vertébrésconstitue une méthode fiable de reconstitution des paléotempératures, grâce àl’interdépendance entre le δ18O de l’apatite des dents, le δ18O des fluides corporels, del’eau ingérée et la température du milieu. L’amélioration et la miniaturisation des techniquesanalytiques a permis d’augmenter la résolution du signal reconstitué, depuis les variations detempérature sur de grandes échelles de temps jusqu’aux variations saisonnières durant laformation de la dent. Cependant, ces variations du δ18O de la dent ne sont pas uniquementdépendantes des variations de température du milieu, mais peuvent également êtreaffectées par d’autres paramètres climatiques, comme la répartition des précipitations aucours de l’année, ou biologique, comme le mode de minéralisation de la dent, l’alimentation,la physiologie de l’animal ou des migrations.Les paramètres biologiques peuvent être estimés dans le cas de taxons possédantdes parents proches dans la faune actuelle. Par exemple, la connaissance des processus deformation et de minéralisation des dents de bovinés actuels permet d’interpréter le signalisotopique de l’oxygène enregistré dans les dents de bovinés fossiles. Ainsi, l’analyse dedents de Bison priscus provenant de l’aven de Coudoulous (Lot, France) a permis dereconstituer les variations saisonnières de température au cours de l’avant-dernier épisodeglaciaire (MIS 6) au Pléistocène moyen, lorsque la région servait de terrain de chasse àHomo neanderthalensis. Le climat était à cette époque plus froid de 4°C en moyenne, maisavec des saisons nettement plus contrastées. Ainsi, si les températures estivales étaientidentiques aux valeurs actuelles, les températures hivernales étaient plus basses de 6-7°C.En milieu marin, les variations saisonnières de température affectent uniquement leseaux de surface. Les plaques dentaires de myliobatidés, un groupe de raies pélagiquesvivant principalement entre 0 et 100 mètres de profondeur, sont un outil potentiel pourreconstituer la paléosaisonnalité. L’étude de plaques dentaires de Myliobatis et deRhinoptera actuels montre que la composition isotopique des dents de ces animauxenregistre des variations de température et de δ18O des eaux de surface. Ainsi, il est doncpossible de reconstituer les caractéristiques des masses d’eau traversées par l’animal. Cetoutil a également un intérêt paléoécologique car il permet de mettre en évidence d’éventuelscomportements migratoires, comme chez certains myliobatidés actuels. L’étude despécimens d’Aetomylaeus provenant du Pliocène de Montpellier (Hérault, France) montredes températures 5°C plus élevées par rapport aux v aleurs actuelles. / The oxygen isotopic composition of the vertebrate tooth enamel is a reliable proxy toreconstruct paleotemperatures based on the dependence of the δ18O of the tooth apatite onthe δ18O of body fluids, on the δ18O of the drinking water, and on the environmentaltemperature. The improvement and the miniaturization of the analytical procedures allowedincreasing the resolution of the reconstructed signal, from paleotemperature variations overgeological times to seasonal variations during the tooth growth. However seasonal variationsof the enamel δ18O do not only depend on temperature variations but can also be influencedby other climatic parameters such as rainfall distribution over the year, or by biological andecological parameters such as tooth mineralization process, diet, physiology or migratorypatterns.Biological parameters can be estimated based on the study of extant relatives inmodern faunas. For example, data on tooth formation and mineralization processes inmodern bovids allow a better understanding of the oxygen isotopic signal recorded in fossilbovid teeth. Thus reconstruction of seasonal variations of temperature during the penultimateglacial episode (MIS 6) has been made possible from the analysis of Bison priscus teethfrom the aven of Coudoulous (Lot, France). Climate was 4°C colder during the middlePleistocene when Europe was still Homo neanderthalensis hunting ground, and seasonswere more contrasted than today. Summer temperatures were similar to modern values, butwinter temperatures were 6-7°C colder.In marine environments, seasonal variations of temperature only affect surfacewaters. Myliobatids are pelagic rays living mostly between 0 and 100 m depth, thus theoxygen isotopic composition of myliobatid dental plates is a potential proxy to reconstruct thepaleoseasonality. The isotopic analysis of modern Myliobatis and Rhinoptera samplesconfirmed that variations of the sea-surface temperature (SST) and the δ18O of seawater arerecorded in the δ18O of myliobatid teeth. Thus it is possible to reconstruct the variations ofseawater temperature during a part of the animal’s life, but it also allows pointing outmigratory patterns in some myliobatid species. Reconstructions of seasonal variations ofSST during the middle Pliocene in Montpellier (Hérault, France) from the δ18O of myliobatiddental plates yielded paleotemperatures 5°C higher than modern values.

This study consisted of two research projects in the Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L. Welsh) alliance, the most extensive of the big sagebrush complex in the Intermountain West. In the first project, we intensively sampled 107 relatively undisturbed, late seral Wyoming big sagebrush sites across the High Desert, Humboldt, and western Snake River Ecological Provinces to investigate vegetation heterogeneity and the relationship of environmental factors with vegetation characteristics. Vegetation characteristics were highly variable across the region. Perennial grass and total herbaceous cover varied more than six and sevenfold, respectively between minimum and maximum values. Sagebrush cover averaged 12%, but ranged between 3 and 25%. With the exception of perennial grass cover (p<0.0001, r²=0.52), limited variability in other vegetation characteristics was explained by environmental variables. In the second project, we investigated the functional role of Wyoming big sagebrush by using undisturbed and sagebrush removed (with burning) treatments and comparing vegetation and microsite characteristics under (subcanopy) to between sagebrush canopy (interspace) zones. Wyoming big sagebrush influenced associated vegetation and microsites. On sites receiving high incidental radiation, perennial grass and total herbaceous cover and density were greater in the subcanopy than interspace zones (p<0.05). On north aspects, these differences were not as pronounced suggesting sagebrush's influence on associated vegetation is site dependent. Temperature extremes were mediated and soil water content was greater in the subcanopy than interspace zones during the growing season. Results indicated that the subcanopy zone can be a more favorable environment to herbaceous vegetation than the interspace zone. Wyoming big sagebrush is important to community resource capture and use. Plots with sagebrush had greater soil water content at the start of the growing season and produced more total biomass compared to where sagebrush had been removed in both post-fire years (p<0.05). However, higher Thurber's needlegrass photosynthetic rates and greater herbaceous cover and production where sagebrush had been removed suggested that more resources were available to herbaceous vegetation in the absence of sagebrush. / Graduation date: 2006

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Submitted by (lucia.rodrigues@ufrpe.br) on 2016-08-25T13:02:14Z No. of bitstreams: 1 Alan Caue de Holanda (1).pdf: 4278080 bytes, checksum: 564351dc83c5e00382ba808429b9f256 (MD5) / Made available in DSpace on 2016-08-25T13:02:15Z (GMT). No. of bitstreams: 1 Alan Caue de Holanda (1).pdf: 4278080 bytes, checksum: 564351dc83c5e00382ba808429b9f256 (MD5) Previous issue date: 2012-02-29 / The Caatinga is one of the only regions in Brazil where its limits are restricted to national territory, and for being the biome fourth in land area in the country, is the most neglected by the political authorities, where there is a strong anthropic disturbance and disorderly exploitation of natural resources, especially for energy, agricultural and pastoral. Given this issue, and the deficiency related to the study of vegetation, is that the present work aims to survey the vegetation in an area of Caatinga, analyze litter production and nutrient; check the rate of decomposition of leaf litterfall of ten species of greatest importance value and quantify the distribution of nutrients in the soil-vegetation. The study was conducted in the remnant forested savanna Riachão Farm located in the municipality of Pombal, PB. For sampling of the adult vegetation were installed 40 plots of 10 m x 25 m in a systematic way, where were inventoried all the individuals with CAP ≥ 10.0 cm. Natural regeneration was evaluated through the implementation of sub-plots of 5 m x 5 m located in the northwestern part of each installment, in which all individuals were sampled with a height H> 1.0 m CNB <10.0 cm. To analyze litter production were installed in the center of each sample unit a collector box with dimensions of 1.0 m2, in which monthly during the period of one year, all material in the boxes were collected and separated by fractions, and 40 plots installed, 16 were selected for realization of analyzes chemistry (N, P, K, Ca and Mg). The decomposition of leaf material was performed for the ten species of highest importance value (VI) recorded in the area in line with the soil respiration. After collecting the leaves, they were distributed in 288 litter bags, and each had a portion of 10.0 g. Samples were collected during one year at intervals of 45 days and then sent to the laboratory for chemical quantification of C and N. To analyze the distribution of nutrients in different compartments of the soilplant system, was collected recent mature leaves from the middle portion of the canopy of ten trees of most important in different orthogonal points, eight soil samples from plots at different depths (0 - 0.1 m, 0.1-0.2 m, 0.2-0.3 m) and portions of organic mantle, all the papers were forwarded to the analyzes chemical. We sampled 1338 individuals in the adult tree shrub component and 365 in natural regeneration. The Shannon diversity index calculated for the adult and regeneration was 1.67 and 1.35 nats individual-1, respectively. Were estimated deposition an annual litter of 3785.67 kg ha-1, the leaf fraction being the largest contributor with 70% and the concentration of nutrients in the litter followed the order Ca>N>K>Mg>P. It was found over a year of the study as a weight loss of 67% and with the soil respiration more intense at night. The C/N rate is relatively low, indicating a higher rate of mineralization. The remaining soil is rich in nutrients and high concentrations of nutrients in the leaves, associated with low concentrations observed in the organic mantle, may be indicative of greater efficiency of the biochemical cycle. / A Caatinga é uma das únicas regiões do Brasil em que seus limites estão restritos ao território nacional, e apesar de ser o quarto bioma em área territorial no país, é o mais negligenciado pelas autoridades políticas, onde se verifica uma forte pressão antrópica e desordenada na exploração dos recursos naturais, principalmente para fins energéticos, agrícolas e pastoris. Diante dessa problemática, e da carência em trabalhos relacionado ao estudo da vegetação, é que o presente trabalho, tem por objetivo fazer o levantamento da vegetação em uma área de Caatinga, analisar o aporte de serapilheira e nutrientes; verificar a taxa de decomposição da serapilheira foliar das dez espécies de maior valor de importância e quantificar a distribuição de nutrientes no sistema solo-vegetação. O trabalho foi conduzido em um remanescente de savana estépica florestada localizada no Sítio Riachão, município de Pombal, PB. Para amostragem da vegetação adulta, foram instaladas 40 unidades amostrais de 10 m x 25 m de forma sistemática, onde foram inventariados todos os indivíduos com CAP ≥ 10 cm. A regeneração natural foi avaliada pela implantação de sub-unidades amostrais de 5 m x 5 m instaladas na parte noroeste de cada parcela, em que foram amostrados todos os indivíduos com altura H > 1,0 m e CNB < 10,0 cm. Para analisar o aporte de serapilheira foi instalada, no centro de cada unidade amostral, uma caixa coletora com dimensões de 1,0 m2, em que mensalmente durante o período de um ano, todo material presente nas caixas foi coletado e separado por frações, e das 40 parcelas instaladas, 16 foram sorteadas para a realização das análises químicas (N, P, K, Ca e Mg). A decomposição do material foliar foi realizada para as dez espécies de maior valor de importância (VI) registradas na área em consonância com a respiração edáfica. Após a coleta das folhas, as mesmas foram distribuídas em 288 litter bags, e que cada uma tinha a porção de 10,0 g. As coletas foram realizadas no período de um ano em intervalos de 45 dias, sendo posteriormente encaminhadas ao laboratório para a quantificação química de C e N. Para analisar a distribuição dos nutrientes nos diferentes compartimentos do sistema solo-planta, coletaram-se folhas recém maduras da porção média da copa das dez árvores de maior VI, nos diferentes pontos ortogonais, amostras de solo de oito parcelas em diferentes profundidades (0-0,1 m; 0,1-0,2 m e 0,2-0,3 m) e porções de manta orgânica, posteriormente todo o material foi encaminhado para a realização das análises químicas. Foram amostrados 1338 indivíduos no componente arbustivo arbóreo adulto e 365 na regeneração natural. O índice de diversidade de Shannon calculado para o adulto e regeneração foi de 1,67 e 1,35 nats individuo-1, respectivamente. Estimou-se uma deposição anual de serapilheira de 3.785,67 kg ha-1, sendo a fração folha a maior contribuinte com 70% e a concentração de nutrientes na serapilheira seguiu a ordem Ca>N>K>Mg>P. Verificou-se ao longo de um ano de avaliação medidas de perda de massa de 67%, com a respiração edáfica sendo mais intensa no período noturno. A relação C/N foi relativamente baixa, indicativo de maior taxa de mineralização. O solo do remanescente é rico em nutrientes, e a alta concentração de nutrientes nas folhas, associada à baixa concentração observada na manta orgânica, pode ser um indicativo de maior eficiência do ciclo bioquímico.