Recent successful drilling operations at Lake El'gygytgyn, NE Russia have recovered sediment cores back to 3.6Ma, representing the longest time-continuous sediment record of past climate change in the terrestrial Arctic. Analysis of the hydrogen isotopic ratio (δD) of specific organic biomarkers allows reconstruction of past hydrological conditions, thereby providing a powerful tool for reconstructing past Arctic climate changes. Compound specific isotopic analysis of sedimentary lipids from this remote basin provides new insights into the climate evolution of the Arctic, capturing the mechanisms and dynamics of the last two glacial-interglacial transitions, potentially enhancing the accuracy of modeled future climate change projections and presenting an opportunity to estimate past polar amplification of climate change. The results of this research document the first continuous, high fidelity continental record of reconstructed δD in precipitation from terrestrial plant leaf waxes in the High Arctic spanning the last 120 ka. The hydrogen isotopic composition of lipid biomarkers were determined from previously obtained Lake El'gygytgyn sediment cores and compared with other multi-proxy evidence of past climate change within the lake basin. The modern isotope hydrology and controls on the δD lipid signal were first established within the El'gygytgyn Basin from modern precipitation, stream and lake waters, ice cover as well as modern vegetation, water column and lake bottom surface sediments in order to provide a modern context to properly constrain and interpret paleoclimatic proxy data. Reconstructed δD records of paleoprecipitation and temperature at Lake El'gygytgyn lead other northern hemisphere climate records (e.g. North Greenland Ice Core Project, NGRIP δ18O records) and are in phase with other continental and Antarctic climate records, suggesting early high northern latitude continental warming prior to established glacial-interglacial transitions. The data set generated here leads to multiple avenues of future work and provides critical insights into Arctic paleoclimate and paleohydrology, contributing to our understanding of high latitude environmental change over geological timescales. Collectively, the results of this dissertation research will provide a context for paleoclimate reconstructions and future organic geochemical and stable isotope analysis. Future application of compound-specific H isotope analyses to long drill cores (recovered in 2009; ~315m of sediment) will potentially provide a quantitative high-resolution record of paleoclimatic and paleoenvironmental changes spanning the last 3.6 Ma.

Big Bone Lick (BBL) is a late Pleistocene and Holocene fossil locality in the Ohio River valley of Kentucky. This study utilized stable isotopes (δ13C, δ18O, and 87Sr/86Sr) in tooth enamel to reconstruct mobility and diet in Bison, as well as diet in Bootherium bombifrons. Isotopic results from seven Bison and two B. bombifrons are reported. Results suggest Pleistocene Bison and Bootherium occupied different dietary niches. Although both had C3-dominated diets, Bison occupied more open environments than B. bombifrons. Two bison from the late Holocene deposit had diets that consisted of more C3 vegetation than Pleistocene bison, which may indicate these individuals occupied a closed C3 landscape. However, one specimen previously identified as late Holocene had diet and mobility patterns consistent with Pleistocene bison, which could indicate temporal mixing. Pleistocene and Holocene Bison have 87Sr/86Sr values that suggest they spent most of their time in places other than BBL.

Growth rates and diet patterns for sympatric pallid sturgeon Scaphirhynchus albus and shovelnose sturgeon S. platorynchus throughout the Missouri River and lower Mississippi River were examined. Pallid sturgeon growth in the Great Plains Management Unit (GPMU) was slower than in other river reaches until age 9 and pallid sturgeon from the Interior Highlands Management Unit (IHMU) and Coastal Plain Management Unit (CPMU) did not differ. No differences in growth between management units were detected for shovelnose sturgeon. Observed differences in growth between pallid sturgeon and shovelnose sturgeon were generally dependent upon which growth model was used, but pallid sturgeon were typically larger after age 4. Diet is considered a primary driver of growth. Stable isotopes are capable of examining diet over longer time periods than gut content studies, but that time frame is dependent on which tissue is selected. Using fin clips, diet of both pallid sturgeon and shovelnose sturgeon was evaluated via stable isotopes. Pallid sturgeon and shovelnose sturgeon trophic position (TP) was influenced by management unit. There was a slight, but not significant, latitudinal trend with pallid sturgeon TP increasing by approximately one full TP between the GPMU and CPMU. Pallid sturgeon growth was negatively related to TP but was unrelated to δ13C in the Missouri River. Shovelnose sturgeon growth was not related to TP, but was negatively related to δ13C in the Missouri River. Dissimilarity in TP combined with differences in δ13C between species suggests low diet overlap between these sympatric species, and neither species should be used as a surrogate for the other for prey consumption studies. Further, pallid sturgeon differences between the GPMU and the rest of the management units suggest that individuals from the GPMU could be managed separately from those in other management units.

While there is a clear link between riparian forests and freshwater organisms, floodplain forests are seldom investigated due to difficulties in sampling structurally complex and periodically inundated habitat. This lack of research has led to large knowledge gaps that hinder our understanding of the conservation value of these unique, complex ecosystems for inland fisheries. Therefore, I aimed to determine how bottomland hardwood forests influence fish taxonomic, functional diversity and food web structure. I hypothesized that fish taxonomic and functional diversity are driven by forest complexity and the aquatic food web structure is driven by terrestrial carbon sources, specifically forest vegetation. Results indicated a higher taxonomic diversity and functional richness in the floodplain forest and that this forest type provides thermal refugia for fish assemblages. Contrary to my prediction, phytomicrobenthos were a primary carbon production source driving some or all of the aquatic food web in a complex floodplain–river system.

No description available.

Concern over rising atmospheric CO2 due to fossil fuel combustion has intensified research into carbon-neutral energy and fuel production. Therefore, bioenergy production has expanded during the last decade, increasing demand for forest-based bioenergy feedstocks. Millions of acres of privately and industrially owned pine plantations exist across the southeastern US, representing a vast area of land that could be utilized to produce bioenergy without significant land-use change or diversion of agricultural resources from food production. Furthermore, loblolly pine (Pinus taeda L.) plantations offer the unique opportunity to utilize space between rows of planted trees to grow an herbaceous bioenergy crop, such as switchgrass (Panicum virgatum L.). This novel forest management regime has the potential to provide positive environmental and economic services, but hinges in part on impacts to soil carbon (C) and nitrogen (N) cycling, availability of belowground resources, and potential negative impacts of competition between pine and switchgrass on plant productivity. Three specific objectives were addressed in this study: 1) compare different bioenergy management regimes in regards to temporal dynamics of N cycling and availability following forest establishment (see Chapter 2); 2) determine the impact of loblolly pine and switchgrass intercropping on microbial N cycling processes (see Chapter 3); and 3) evaluate chemical and physical mechanisms of soil organic matter (SOM) stabilization and test their sensitivity to pine-switchgrass intercropping (see Chapter 4). The study site was located in the Lower Coastal Plain physiographic province in Lenoir County, North Carolina, USA (35-12'59'' N; 077-26'13'' W). Soils were mapped as Pantego (fine‐loamy, siliceous, semiactive, thermic Umbric Paleaquults) or Rains (fine‐loamy, siliceous, semiactive, thermic Typic Paleaquults) soil series, both of which are very poorly drained. However, previous site management in the late 1960’s and early 1970’s included installation of ditches to lower the water table and reduce saturation at the soil surface. Additionally, bedding of soil in rows was used to raise root systems of planted loblolly pine seedlings above the water table, increase soil aeration, and reduce competition. Space between bedded rows of pine trees was referred to as the interbed. Results from Chapter 2 showed that switchgrass significantly reduced interbed soil NH4 + and NO3 - concentrations by 39% and 60%, respectively, over the course of the timeframe (30 months) of this study. Surprisingly, in beds of the pine-switchgrass treatment significant increases in NO3 - concentration were measured from July - December 2011. From Chapter 3, gross N mineralization rates ranged from 0.18 - 4.7 µg N g -1 soil d-1 , while gross nitrification rates ranged from 0.02 - 0.47 µg N g-1 soil d-1 . At the 0-5 cm depth in switchgrass interbeds, gross N mineralization was reduced from April to November potentially reflecting microbial C limitations due to reduced soil C concentrations. At the 0-5 cm depth in beds of the pine-switchgrass treatment, gross N mineralization rates were elevated by 1.29 µg N iii g -1 soil d-1 in November and 1.02 µg N g-1 soil d-1 in February on average corresponding to a 305% and 193% increase, respectively. From Chapter 4, total C content in beds and interbeds ranged from 15 to 88 Mg C ha-1 and was reduced by 27% in beds of the pine-switchgrass treatment. Average C concentration for aggregate fractions was significantly lower in beds of the pine-switchgrass treatment at 0-5, 15- 30, and 30-45 cm depths, amounting to ~23%, ~28%, and ~34% reduction, respectively. Values of δ 13C for the >2000 µm aggregate size fraction at the 0-5 cm depth were diluted, corresponding to estimates of 13 - 25% of the >2000 µm C pool comprised of new pine-derived C. For SOM fractionated by density, elevated C concentrations were found in the occluded light fractions in both beds and interbeds of the pine-switchgrass treatment. Enriched δ13C in occluded light fractions led to estimates of 2.5 - 12.5% of this C fraction comprised of new switchgrass-derived C. In the free light fraction, new pine-derived C accounted for 15% and 9% of C at the 5-15 and 15-30 cm depth, respectively. Three overarching conclusions were generated from my research: 1) switchgrass grown between loblolly pine trees effectively utilized excess soil NH4 + and NO3 - when N availability was high following harvesting of a mature plantation proceeded by establishment of a second rotation of loblolly pine (see Chapter 2); 2) gross N mineralization rates were reduced under switchgrass during the growing season when soil C availability was low, but were elevated under switchgrass and adjacent loblolly pines when switchgrass was dormant and C availability was likely higher (see Chapter 3); and 3) SOM stabilized by physical or chemical mechanisms responded differently to pine-switchgrass intercropping, with losses in aggregate-stabilized C and gains in occluded, mineral-stabilized C. Furthermore, losses of aggregate C was associated with a significant reduction in total soil C in beds of the pine-switchgrass treatment. Results from 13C mass balance suggested incorporation of switchgrass-derived C into occluded light fractions of beds and interbeds. Finally, incorporation of new pine-derived C into the >2000 µm aggregate size fraction and free light fraction indicate pine inputs of particulate organic matter into these SOM fractions in beds of the pine-switchgrass treatment (see Chapter 4). I hypothesize that loblolly pines have increased root growth in beds in response to competition with switchgrass for N in the interbed, thereby alleviating seasonal microbial C limitations and stimulating microbial N cycling processes and increasing plant-available N. Overall, this research suggests that soil C and N cycling in pine plantations is altered by intercropping of pine and switchgrass. Through a mechanistic understanding of how C and N are cycled in forests and the impact of various forest management regimes on soil C and N cycling, effective management strategies can be implemented to utilize forests for intensive biomass production while limiting loss of soil C and N, and in some cases even enhancing soil C and N retention. Future research initiatives should seek to unravel the complex belowground interactions between roots of different plant species and soil microbial communities competing for limiting resources. Understanding how these interactions drive soil C storage, N cycling and availability, and forest productivity will ultimately improve resource utilization in these managed ecosystems as well as our basic understanding of how natural and managed ecosystems function. / Ph. D.

No / Bone collagen carbon and nitrogen stable isotope ratios were obtained from three La Tène period inhumation cemeteries in the Czech Republic (Kutná Hora-Karlov, Radovesice I and Radovesice II) and 16 Hallstatt period inhumations in northern Austria. Results indicate that during the La Tène period in Bohemia, overall diet was based on animal protein and plant foods following the C3 photosynthetic pathway, although ¿13C values for two individuals from Kutná Hora-Karlov indicate at least some contribution from C4 plant foods, most likely millet. At Kutná Hora-Karlov, more positive ¿15N values for male individuals buried with items of iron weaponry indicate the existence of a differential dietary system within the male population based on individual ¿warrior¿ status. A comparison with data from a number of Hallstatt period inhumations in northern Austria and a previously published study of a Hallstatt period site in Slovenia [Murray, M.L., Schoeninger, M.J., 1988. Diet, status, and complex social structure in Iron Age Central Europe: Some contributions from bone chemistry. In: Gibson, D.B., Geselowitz, M.N. (Eds.), Tribe and Polity in Late Prehistoric Europe: Demography, Production and Exchange in the Evolution of Complex Social Systems. Plenum Press, New York, pp. 155¿176] enables an examination of the spread of millet as a major dietary component. This data will be of use to studies of diet in prehistoric Europe and provides evidence for dietary divisions relating to social stratification during the La Tène B¿C, a period often seen as less complex than the preceding Hallstatt period.

Yes / In this study, period-specific dietary trends, along with socio-economic and religious influences on foods consumed by Pictish and medieval inhabitants from Portmahomack are investigated. Bone collagen from human adults (n = 137) and fauna (n = 71) were analysed for stable carbon and nitrogen isotope ratios to enable dietary reconstructions of the whole adult skeletal assemblage. Adult mean δ13C and δ15N values from all periods (6th to 17th century) were −19.5‰ ± 1.3‰ and 13.3‰ ± 1.7‰ respectively. A diachronic change in diet between early medieval Pictish lay and monastic communities (periods 1–3) and the later medieval parish layfolk (periods 4–5) was found that suggests changing socio-economic and religious influences, along with age and gender differences in diet that reflect possible divisions in labour and status. Faunal data also reflected a diachronic change in diet, most likely related to a change in animal husbandry practices over time. This is the first large-scale study on the Portmahomack assemblage and presents new isotope data to provide a more comprehensive insight into Pictish and medieval subsistence patterns, along with evidence of how religious and social foci may influence diet over time. Such comprehensive investigations can only be adopted by analysing the whole skeletal assemblage, providing robust faunal baselines and inter- and intra-site comparisons. Most importantly, this significant new evidence fundamentally changes our knowledge of diet and subsistence in medieval Scotland and the potential influences therein. / Supported by grants from the NERC Isotope Geosciences Facility Steering Committee (IP‐1302‐0512), the Arts and Humanities Research Council (AH/I019103/1), and Historic Scotland (AMJ/4208/4).

Yes

Yes / Objectives: This study presents isotopic information for incremental dentine collagen and bone bulk collagen from individuals from the Canary Islands (Tenerife and Gran Canaria) to explore dietary differences during childhood life. Materials and Methods: Eight individuals have been studied, which comprises 122 δ15N and δ13C incremental dentine measurements and eight bulk bone collagen analyses. A baseline of potentially consumed food sources has been developed for comparative purposes. A FRUITS model of probable contributions of each food source towards the diet of each individual has been developed. All samples but one belongs to the later period of indigenous occupation of the archipelago. Results: The dentine collagen data are presented in correlated δ13C and δ15N plots per individual, showing the isotopic changes throughout time. δ15N values for each individual tend to be variable whereas δ13C data are generally more stable with a range of +9.1 to +14‰ for δ15N and –17.4 to –20.8‰ for δ13C. Conclusion: The isotopic analysis allows for the reconstruction of 8 dietary profiles, which allow us to estimate the different dietary protein sources. The FRUITS model shows different percentages of the primary food sources for each individual. Where both δ13C and δ15N are elevated, this could be indicative of a higher marine contribution to the diet. There appear to be two main dietary profiles identifiable in the dataset and these may be related to changes in status or place of residence. Short-term variations in δ13C and δ15N and opposing co-variance of isotopic values can be indicative of nutritional stress, although metabolic changes during growth are also considered. / PhD grant from Universidad de La Laguna—Fundación La Caixa (“Contratos Predoctorales para la formación de doctores ULL-2015”), MINECO (Ministerio de Economía y Competitividad) project “Guanches y europeos en Las Cañadas del Teide, Ocupación, Producción y Comunicación” (HAR2015-68323-P), “Erasmus+ Scholarship” given by the University of La Laguna, ERC Starting Grant project IsoCAN (grant 851733, European Comission) and the projects RTI2018-101923-J-I00 and RYC2019-028346 (Ministerio de Ciencia e Innovación) / The full-text of this article will be released for public view at the end of the publisher embargo on 2 Aug 2024.