The Relationship of Climate to the Stable Isotopic Composi- tion of Hackberry (Celtis) Endocarps: a Potential Means of Paleoenvironmental Reconstruction in the Great Plains

拟议综合研究的长期目标是 利用朴树内果皮的特殊成分 用同位素方法重建古环境 这个项目将量化稳定的碳和氧同位素 内果皮有机无机成分组成 反映了环境条件以及遗传变异 影响这些关系。 朴属果实的内果皮主要 由文石组成，但也含有少量的有机物 C. 高矿物质含量可能是朴属内果皮 是一种常见的、保存完好的新生代植物遗迹 大平原的沉积物 我们建议进行实验 以确定单个环境参数的影响 （光照强度、水势、温度、湿度） 各种植物成分的δ C 13和δ O 18值， 有机质和碳酸盐的同位素组成 朴树内果皮 内果皮同位素的现代关系 将通过收集朴属植物来检查与区域气候的比率 水果，组织和气候数据，来自美国许多地方 States. 我们将建立气候和气候变化之间的预测关系， 和稳定的同位素值通过采样的一个子集的朴树从 美国农业部的一项实验涉及120多个种质资源。 这些实验在美国的12个地点进行， 整个南北温差以及东西温差 降雨量和大气水分亏缺范围。 的影响 成岩作用对同位素比值的影响及其应用意义 朴属植物在新生代古气候研究中的作用，将通过 短期实验。 如果这些研究结果令人鼓舞， 然后，我们将提交一份提案，开始第二阶段的工作， 在这个项目中，我们将收集，并进行同位素分析， 大平原全新世至渐新世沉积物的内果皮。

The long-term goal of the proposed integrated research is to exploit the peculiar composition of hackberry (Celtis) endocarps for an isotopic approach to paleoenvironmental reconstructions. This project will quantify how the stable C and O isotopic composition of organic and inorganic components in the endocarps reflect environmental conditions and how genetic variability affects these relationships. Endocarps of Celtis fruit mainly consist of aragonite, but also contain smaller amounts of organic C. The high mineral content may be one reason why Celtis endocarps are a common, and well-preserved, plant remnant in Cenozoic sediments of the Great Plains. We propose to conduct experiments to determine the effect of individual environmental parameters (light intensity, water potential, temperature, humidity) on the delta C 13 and delta O 18 values of various plant components and on the isotopic composition of organic matter and carbonate in Celtis endocarps. The present relationship of endocarp isotope ratios to regional climate will be examined by collecting Celtis fruit, tissue, and climate data, from many locations in the United States. We will establish predictive relationships between climate and stable isotope values by sampling a subset of Celtis trees from a USDA experiment involving more than 120 sources of germplasm. These experiments at 12 sites in the United States span the entire north-south temperature range as well as the east-west rainfall and atmospheric water deficit ranges. The effects of diagenesis on the isotope ratios, and its implications for the use of Celtis in Cenozoic paleoclimatic studies, will be examined via short-term experiments. Should these studies prove encouraging, we will then submit a proposal to begin a second phase of the project in which we will collect, and isotopically analyze, endocarps from Holocene to Oligocene sediments of the Great Plains.