Carbon Isotopic Studies of Fossil Tooth Enamel and the Development of C4 Ecosystems

9310546这项建议是为了研究化石牙釉质的碳同位素组成，以确定过去2000万年来哺乳动物的饮食。C4植物与C3植物在同位素上是不同的。因此，这项研究将确定C4生态系统的发展时间，这些生态系统通常以牧草为主。这项拟议的研究包括三个部分：1)识别可能改变牙釉质同位素浓度的成岩变化；2)准确确定C4生态系统在几个大陆上发展的时间；3)确定北美马匹的饮食变异性。根据初步数据，新旧大陆C4生态系统的明显同步发展表明了一种全球生态变化，可能与大气中二氧化碳变化有关。这项研究将确定不同大陆上以C4为主的生态系统首次显著出现的时间。具体地说，将研究来自北美、欧洲、亚洲和非洲的马化石。这项研究是记录全球草原生态系统发展的第一次尝试。鉴于这些C4生态系统同时在不同的大陆上发展，那么它们的演变很可能与全球生态变化密切相关。了解这些变化及其后果对于预测和准备未来随着大气二氧化碳水平继续上升而发生的变化至关重要。***

9310546 Cerling This proposal is to study the carbon isotopic composition of fossil tooth enamel to determine the diet of mammals in the last 20 million years. C4 plants are isotopically different from C3 plants. Therefore, this study will determine the timing of development of C4 ecosystems, which are usually dominated by grasses. The proposed research has three parts: 1) to identify diagenic changes that may alter the isotopic concentration of tooth enamel, 2) to precisely determine the time that C4 ecosystems developed on several continents, and 3) to establish the variability of diet in horses of North America. Based on preliminary data, the apparent synchronous development of C4 ecosystems in the Old and New Worlds suggests a global ecological change, perhaps related to changes in atmospheric changes in CO2. This research will establish the time of the first significant appearance of C4-dominated ecosystems on different continents. Specifically, fossil horses from North America, Europe, Asia, and Africa will be studied. %%% This research represents the first attempt to document the development of grassland ecosystems worldwide. Given that these C4 ecosystems developed simultaneously on different continents, then their evolution is most likely closely tied to global ecological change. Understanding such changes and their consequences is vital to predicting and preparing for future changes as atmospheric CO2 levels continue to rise. ***