Climate Effects on Stable Carbon Isotope Proxies for Paleovegetation in Meade Basin, Kansas

Lauria, Cara Marie

Graduate Thesis Or Dissertation

Climate Effects on Stable Carbon Isotope Proxies for Paleovegetation in Meade Basin, Kansas Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/ws859f86t

Abstract

Paleovegetation proxies inform scientists not only about what climate and ecosystems may have looked like through Earth’s history, but also give us the ability to predict what today’s global change may bring for modern ecosystems. Carbon isotope ratios of soil organic matter (SOM) and pedogenic carbonates record relative proportions of C₄-derived biomass. Each soil constituent is thought to form under different soil climate conditions. Soil organic matter is thought to form under cooler and wetter conditions when climates favor the production of C₃ plant biomass. Pedogenic carbonates are thought to precipitate during the warmest and driest parts of the year, when climates favor the production of C₄ plants and C₃ plants may exhibt water stress. In this study, I investigate if the stable carbon isotopic signatures of SOM and pedogenic carbonates record climate induced vegetation signals. I analyzed and compared the carbon isotope ratio of vegetation collected under drought conditions and wet conditions, SOM, and pedogenic carbonates from four sites that vary in vegetation community and topography in Meade Basin, Kansas. Results from this study suggest carbon isotope values of carbonates and SOM reflect carbon isotope values of vegetation from warm and dry climates and/or values that are ¹³C-enriched relative to warm and dry vegetation. The degree to which the carbon isotope ratio of SOM and carbonates are enriched relative to vegetation, may be controlled by the local topography. Carbon isotope ratios of SOM and carbonates are become heavier relative to warm and dry vegetation as topography increases. These findings suggest SOM and carbonates formed in lowlands may incorporate more of a vegetation derived carbon isotope ratio, while proxies formed in uplands may incorporate more ¹³C-enrichment affects from influences of heavy atmospheric CO₂ and discrimination from decomposition.

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