The diploma thesis deals with the study of stable isotopes of oxygen and carbon of Cretaceous rocks from the Jičín volcanic field. The aim of the thesis is to identify isotope alterations in Cretaceous sediments transported by basic magmas in the form of xenoliths and to determine the origin of oxygen and carbon of hydrothermal vein carbonates that penetrate the bodies of neovolcanites. The study is divided into two parts. The theoretical part summarizes in general the stratigraphy of the Czech Cretaceous Basin and Cenozoic volcanism of the Bohemian Massif, geochemistry of stable isotopes of oxygen and carbon and geology of studied localities in the Jičín volcanic field. The practical part presents a detailed isotope study of Hřídelec, Kulatý vrch, Zebín, Veliš and Kunětická hora localities. Cretaceous rocks from xenoliths in these neovolcanites show extreme variability in the isotopic composition of both carbon (from 0,15 to -11,1 ‰ V-PDB) and oxygen (from -5,4 to -22,9 ‰ V-PDB). They significantly exceed the variability of the isotopic composition of diagenetically altered Cretaceous rocks from the same area. The wide range of oxygen isotope composition is the result mainly of fluid temperature variability (approx. 300 - 20 řC), which isotopically altered Cretaceous sediments. Carbon isotope...

<div>Animal species that consume carrion provide an essential ecosystem service by recycling the resource’s nutrients intothe ecosystem. Carrion is an unpredictable and ephemeral resource that is variable across a landscape and is an important resource to many taxa. Furthermore, the colonization of small vertebrate carcasses by different species influences competition and coexistence dynamics, which in turn influence species dominance. The American burying beetle, <i>Nicrophorus americanus</i>(ABB) has recently experienced a dramatic decline in abundance and geographic range. An essential requirement of the ABBs life cycle is the availability of small vertebrate carcasses for reproduction. We know little about the preferred carrion base necessary to support a healthy ABB population. However, we know that reproduction is costly in buying beetles, and physiological trade-offs associated with resource use likely influences metabolic activity, fecundity, and survivorship. Furthermore, successful monitoring of wildlife populations requires reliable estimates of abundance, dispersal, and population demographics. This is often problematic within ABB populations because they are elusive, nocturnal, often occur at low population densities, and are a species of conservation concern. These factors constitute a management and conservation challenge in ecology and conservation biology. Therefore, identifying and evaluating the resources used for reproduction, along with life history trade-offs associated with resource use, in addition to species abundance within a habitat are key requirements for this species’ conservation and management. We used stable isotope analysis of carbon and nitrogen to determine the carrion base used by burying beetles in situ. Additionally, we evaluated resting metabolic rate and the energetics of prehatching parental care using flow through respirometry. Finally, we investigated the utility of using photographs with an individual identification machine learning software program paired with program MARK to estimate population abundances of burying beetles.<br></div><div><br></div><div>Between populations, ABBs are not specializing on either avian or mammalian carrion but are using both natural and provisioned carrion for reproduction. Furthermore, among co-occurring burying beetle species, we observed large niche overlap in both populations. Periods of sexual development and prehatching parental care were periods of elevated metabolic activity, which provides insight into life-history tradeoffs associated with resource quality. Carcass size did not significantly influence the metabolic rate of parents, however, the number of days needed to 13prepare a small carcass was significantly shorter compared to large carcass preservation. Furthermore, beetle pairs on larger carcasses accumulated significantly larger metabolic cost over the course of parental care. Additionally, using digital images of naturally occurring spot patterns on beetles’ elytra, we tested the feasibility and the application of photographic mark-recapture (PMR) using machine learning software. We demonstrated the utility of using PMR in estimating population abundance for Nicrophorusspp. based on elytral spot patterns. Future research is needed to fully quantify reproductive resource use over time, and how it influences ABB abundance in extant and reintroduced populations. For successful management and reintroduction of ABBs, managers must consider the resources used for reproduction, the composition and availability of appropriately sized potential reproductive carrion, they should limit intra-/interspecific competition for carrion resources and need accurate data on species abundance.<br></div><div><br></div><div><br></div>

Arctic tundra wetlands support abundant waterbirds, but invertebrate prey communities may change with climate warming. Increased influx of nutrients and labile dissolved organic matter (DOM) from thawing permafrost may alter the relative importance of organic matter (OM) sources, with associated changes in relative biomass of taxa dependent on different sources. In six wetland types, we used stable isotopes (δ13C, δ15N) to compare contributions of four OM sources (periphytic microalgae, cyanobacteria, macrophytes, and peat) to the diets of nine macroinvertebrate taxa. Relative OM contributions within invertebrate taxa were similar among wetland types. Cyanobacteria comprised only 2–7% of OM sources for all taxa in shallow wetland types (<1 m), but up to 25% for oligochaetes and Physidae in deeper wetlands. Macrophytes were minor OM sources (<13%) in all wetland types except deep open lakes (21–26%). Peat typically comprised 20–40% of OM sources except for Physidae (mostly 50–80%). Microalgae were the dominant OM source for most taxa (47–78%, mean ⁓60%), although less for Oligochaeta and much less for Physidae (9–32%). High periphyton production with very depleted δ13C values likely results from continuous daylight illuminating shallow depths, high N and P levels, and very high pCO2 derived from bacterial respiration of DOM leached from thawing permafrost. Invertebrate consumption of microalgae and peat appears often to involve bacterial intermediates. Impacts of warming on invertebrate prey availability will likely depend not on shifts in OM sources, but on changes in overall area or number of shallow ponds.

Black Carp (Mylopharyngodon piceus) is an invasive fish species native to Asia that has become increasingly abundant within the Mississippi River Basin during the past decade. Originally introduced to control snails that are an intermediate host for trematode parasites of fishes in aquaculture ponds, Black Carp are now present in several rivers in the U.S. and represent a potential threat to threatened and endangered mussel populations. Black Carp have historically been classified as molluscivores; however, a recent study that examined gut contents of Black Carp collected from the Mississippi River Basin indicated that Black Carp are opportunistic consumers that prey upon a wide variety of invertebrates and are flexible in their feeding modes. Despite the potential for Black Carp to compete with native riverine fish species for invertebrate prey, only one published study has compared Black Carp trophic position with that of native fishes in a small portion of the Black Carp’s invaded range. Therefore, the objectives of this study were to assess trophic overlap between Black Carp and two fish species native to the Mississippi River Basin using isotopic niche analysis and gut contents analysis. Dorsal muscle tissue samples were collected from Black Carp, Freshwater Drum (Aplodinotus grunniens), and Blue Catfish (Ictalurus furcatus) and analyzed for δ13C and δ15N to assess each species’ isotopic niche. Freshwater Drum and Blue Catfish gut contents were also removed and analyzed and compared to published Black Carp stomach contents data. Gut contents analysis indicated differences in diet composition between Black Carp and the two native fish species. Chironomidae had the highest frequency of occurrence (67%) and percent of taxa by number (47%) for Freshwater Drum. Trichoptera had the highest frequency of occurrence (58%) and percent of taxa by number (30%) for Blue Catfish, and Gastropoda had the highest frequency of occurrence (16.5%) of any specific prey taxa for Black Carp. Black Carp showed low isotopic niche overlap (≤47%) with both native species when muscle tissue δ13C and δ15N data from all fish collection locations were combined and when assessment of isotopic niches was restricted to the subset of locations where all three species were collected. Isotopic niche overlap was also low (10-48%) between Black Carp and both native species when isotopic niches were compared at individual collection locations. Intraspecific isotopic niche overlap among fish collection locations was highly variable (0-69%) within each of the three species, highlighting the need to assess interspecific isotopic niche overlap by collection location. Broad isotopic niches exhibited by Black Carp in the Mississippi River and tributaries are indicative of substantial trophic diversity among individuals and use of multiple basal energy sources, consistent with a recently published study which found that Black Carp diet composition differed among individuals and that Black Carp consumed a variety of invertebrates, including non-benthic taxa.

Ecomorphological specialization within Catostomidae in several large western North American lakes has produced populations including typical benthic suckers (Catostomus) and lakesuckers (Chasmistes), mid-water planktivores, with a continuum of morphologies existing between them. All extant lakesuckers are endangered, and population declines have been attributed in part to hybridization with sympatric Catostomus spp. Chapter 2 describes assessment for concordance of morphological and genetic variation in suckers in Utah Lake, Utah (June sucker, Chasmistes liorus; Utah sucker, Catostomus ardens; and suckers of intermediate morphology) by comparing a morphological analysis with amplified fragment length polymorphism and microsatellite analyses. Suckers were differentiated using characters associated with presumed feeding strategies: zooplanktivory (June sucker) and benthivory (Utah sucker). No molecular evidence was found for deep genetic divergence between morphs or for hybridization among ancient lineages. Slight population structuring accompanied substantial morphological variation. Chapter 3 describes the investigation of distribution and movement, spawning behavior, and diet of suckers in Utah Lake and their growth at different densities in a laboratory experiment. Acoustic / radio telemetry revealed little difference in movement and distribution of June sucker and Utah sucker or in timing of spawning runs. Stable isotopes analysis revealed that Utah sucker were enriched in 13C relative to June sucker as presumed diets would predict. Intermediate morphs were intermediate for δ13C and δ15N. Neither species nor density was a significant predictor of growth rate of June sucker or Utah sucker reared at different conspecific densities. Chapter 4 examines morphology, genetics, and diet of the sucker population inJackson Lake, Wyoming, once home of the extinct Snake River sucker, Chasmistes muriei, a lakesucker known from a single specimen. Currently, suckers in Jackson Lake are identified as Utah sucker; however, recently sampled individuals resemble lakesucker. No molecular evidence was found for deep genetic divergence between lakesucker and benthic morphs or for hybridization among ancient lineages. The benthic morph was significantly enriched in 13C relative to the lakesucker morph, consistent with presumed diets. Morphologically, the lone Snake River sucker holotype specimen grouped strongly with extant lakesucker morphs, suggesting that the status of the Snake River sucker be updated accordingly.

Sagebrush-dominated ecosystems are being transformed by wildfire, rangeland improvement techniques, and exotic plant invasions. These disturbances have substantial effects on the composition and structure of native vegetation, but the effects on ecosystem C and N dynamics are poorly understood. To examine whether differences in dominant vegetation affect the quantity and quality of plant organic matter inputs to soil, ecosystem C and N pools and rates of plant turnover were compared among historically grazed Wyoming big sagebrush, introduced perennial crested wheatgrass, and invasive annual cheatgrass communities. Since low soil moisture during the summer may inhibit the microbial colonization of plant detrital inputs and result in C-limitations to microbial growth, soils were treated with an in situ pulse of plant detritus prior to the onset of the summer dry-season, and rates of soil C and gross N cycling were compared between treated and untreated soils. Finally, because plant detritus is the dominant form of labile C input to soil microbes over a large portion of the year, the decomposition of 13C-labeled annual grass detritus was used to determine the importance of plant detritus versus soil organic matter as microbial substrate. Results revealed large differences in ecosystem C and N pools, and in the quantity of plant C and N inputs to soil among vegetation types, but differences in soil C and N cycling rates were more subtle. Plant biomass pools were greatest for sagebrush stands, but plant C and N inputs to soil were greatest in cheatgrass communities, such that rates of plant C and N turnover appeared to be accelerated in disturbed ecosystems. Earlier release of plant biomass to soil detrital pools stimulated N availability to a greater extent than C availability relative to untreated soils, and this effect could not be predicted from the C:N stoichiometry of plant detritus. Finally, in situ decomposition of cheatgrass detritus was rapid; however, there was no clear evidence of a time-lag during summer in microbial colonization of recently released plant detritus, and microbial consumption of plant detritus did not result in N-limitations to microbial growth.

This study addressed a fundamental question in applied ecology and conservation; what is the predatory impact of introduced piscivorous sport fish on imperiled native fish populations? More specifically, which of many introduced species and size-classes represent the greatest threats and should be targeted for control? In order to explore this important question, an integrated analysis of stable isotopes, quantified observed diet analysis, and stable isotope mass-balance models were used to quantify trophic interactions. These tools were used to construct food web models that were then compared to draw inferences regarding the relative contribution of prey fish, including rare native fish, to the diet of introduced sport fish. The stable isotope-derived food web illustrated a slight decoupling in energy flow between a pelagic and a benthic-littoral sub-web. The quantified diet analysis suggested piscivory was low overall, and that the introduced sport fish assemblage relied heavily on zooplankton and aquatic insect prey. The integrated stable isotope and quantified diet analysis demonstrated that the consumption of prey fish, particularly pelagic prey fish, was typically underestimated using stomach content analyses. From the evaluation, comparison, and integration of food web models, I suggest that substantial predation was occurring on the early life stages of Utah Lake fishes, including native fishes, and it was not being observed using stomach content analysis. My comparative modeling demonstrated that introduced sport fish are an impediment to native fish conservation and identified the small size-class of white bass as the most immediate threat.

The Mountain Home (MH) geothermal system of the western Snake River Plain (SRP) magmatic province was discovered in 2012 by the Snake River Geothermal Drilling Project. Artesian flowing water with a temperature of 150°C was encountered at a depth of 1745 m below ground surface (mbgs) and extensive mineralized fracture networks of pectolite-prehnite, calcite, and laumontite were discovered in the recovered core. The objectives of this study are to: 1) describe the thermal and compositional history of past geothermal fluids, and 2) compare these fluids to modern fluids in order to characterize the evolution of the MH geothermal system and the geothermal potential of the western SRP. Core observations, thin section petrography, X-ray diffraction, and Electron Microprobe analyses were performed in order to describe mineral parageneses of various alteration zones. Carbon and oxygen stable isotope ratios along with temperatures of homogenization from fluid inclusions in hydrothermally precipitated calcite were measured along ~100 m of basalt core from 1709-1809 mbgs. The d13CPDB values in calcite range from -7.2 to -0.43 ‰ and d18OPDB values range between -20.5 and -15.9 ‰. An anomalous zone from 1722-1725 m depth displays a range in d13CPDB and d18OPDB of -1.9 to +0.88 ‰ and -17.1 to -8.1 ‰, respectively, suggesting non-equilibrium fractionation due to boiling. Carbon isotopic ratios suggest a mixture of deep-seated mantle derived and meteoric fluids. Fluid inclusion microthermometry has identified primary inclusions with trapping temperatures ranging from 168-368°C. A calcite-water geothermometer used to calculate paleo-fluid oxygen isotopic composition (-0.43 to +7.2 ‰ SMOW) and a comparison with present-day fluid oxygen isotopic composition (-3.2 ‰ SMOW) reveals a cooling trend with potential mixing of meteoric waters and deeply derived fluid. The MH geothermal system has cooled over time and reflects potentially less, if any magmatic fluid input presently into the system as there was in the past.

Climate warming in recent decades has resulted in more frequent and severe drought events in the western United States. These changes are projected to continue, making it exceedingly important to understand how forests respond to severe drought stress, and how we can manage these forests to reduce mortality during future events. The 2012-2015 California drought is a recent example of a severe, multi-year drought that was coupled with an epidemic-scale outbreak of western pine beetle, killing nearly 90% of ponderosa pines in the central and southern Sierra Nevadas. In the first portion of this study, we compared pairs of surviving and dead ponderosa pines following this drought event to determine how the surviving trees were able to survive. We were also interested in how closely ponderosa pine tree-rings were recording ecosystem responses to this drought event. In the second portion of this study, we compared tree-ring growth rates and stable isotopes to data from an on-site flux tower to determine whether tree-rings were recording important information regarding ecosystem carbon and water fluxes during this severe drought event. Overall, we sought to better understand how the 2012- 2015 California drought event affected ponderosa pines to inform future management practices in forests of the western United States.

L’Hémisphère Sud, et plus précisément le sud de l’Amérique du Sud, sont très sous-représentés dans les reconstitutions climatiques globales du fait d’un manque de données paléoclimatiques robustes. Mes travaux de thèse ont donc porté sur l’évaluation de l’archive naturelle cernes d’arbre, abondante le long de la Cordillère des Andes, comme traceur paléoclimatique. Je me suis ainsi appliquée à étudier la réponse régionale de deux espèces d’arbre (Fitzroya cupressoides et Nothofagus pumilio) natives du nord de la Patagonie (41°S, Argentine) aux forçages climatiques externes en analysant leurs différents paramètres physiques. Pour cela, j’ai commencé par déterminer l’influence du climat local et de grande échelle sur leur croissance en étudiant les variations temporelles de leurs largeurs de cerne, puis j’ai essayé d’extraire le signal climatique enregistré dans la composition isotopique de l’oxygène et du carbone de la cellulose de ces cernes. Deux résultats majeurs de ma thèse ont émergé: j’ai mis en évidence (1) des réponses non-linéaires de la croissance au cours du temps liées aux changements de régimes climatiques et, (2) le fort potentiel du delta18O et delta13C de la cellulose pour enregistrer les variations de température d’été-automne sur une large région aux latitudes moyennes de l’Amérique du Sud (35°-55°S). Du fait des relations fortes qui les lient aux températures, les outils isotopiques peuvent être utilisés pour reconstituer des chronologies de température mais aussi des modes climatiques tels que l’Oscillation Antarctique. / The Southern Hemisphere, and particularly southern South America, are very under-represented in global climate reconstructions due to a lack of robust paleoclimatic data. My thesis was therefore focused on the evaluation of the tree-ring archive, which is widespread along the Andes, as a paleoclimatic tracer. I studied the regional response to external climate forcing of two native species (Fitzroya cupressoides and Nothofagus pumilio) in northern Patagonia (41°S, Argentina), by analysing their different physical tree-ring parameters. In this perspective, I analysed the temporal variations of the width and of the oxygen and carbon isotopic compositions of the cellulose of their rings and related them to local and large-scale climate variations. Two major results of my thesis have emerged: I highlighted (1) non-linear growth responses over time related to shifts in climate regimes and, (2) the potential of cellulose delta18O and delta13C to record summer-autumn temperature variations over a large area in the mid latitudes of South America (35°-55°S). As their variations are strongly linked to temperature the isotopic tools can be used to reconstruct chronologies of temperature but also of climate modes such as the Southern Annular Mode.