Stable isotope measurements of carbon dioxide

稳定同位素的测量已成为环境研究中区分消费者食物来源和跟踪生态系统中生物地球化学通量的一个有价值的工具。 在自然界中，同位素变异的发生是由于化学和物理过程优先浓缩一种同位素，或者因为生物体更有效地代谢一种同位素而不是另一种。可将示踪同位素引入生态系统，以便在直接测量无法测量的情况下测量转移和转化率。本建议书中要求的气体工作台装置将完善我们现有的实验室设施，以便对二氧化碳进行同位素分析，用于以下领域的工艺级研究：1.土壤碳地球化学--土壤呼吸中二氧化碳的同位素特征在很大程度上反映了源有机质的组成。这一方法将用于描述自然和人为干扰后土壤恢复过程中的碳固存。2.微生物生态学-土壤生物多样性是生态系统功能的核心，但迄今为止基本上尚未探索。 一系列的标记实验将土壤微生物群落的组成与它们介导的过程联系起来。

Measurements of stable isotopes have become a valuable tool in environmental studies to differentiate between food sources to consumers and to follow biogeochemical fluxes through ecosystems.  In nature, isotopic variations occur due to chemical and physical processes that preferentially concentrate one isotope, or because organisms more efficiently metabolize one isotope over another. Tracer isotopes may be introduced into ecosystems to permit measurements of rates of transfer and transformation when direct measurements do not. The Gas Bench unit requested in this proposal will complete our existing laboratory facility as to allow isotopic analysis of carbon dioxide for process-level research in the area of: 1. Soil carbon biogeochemistry-- the isotopic signature of carbon dioxide in soil respiration largely reflects composition of the source organic matter. This approach will be used to characterize carbon sequestration during soil recovery following natural and anthropogenic disturbance. 2. Microbial ecology-- soil biodiversity is central to ecosystem functioning yet to date has mainly remained unexplored.  A series of labeling experiments will relate composition of the soil microbial communities to the processes they mediate.