Global distribution of deltaD values in C-bonded hydrogen of soil organic matter

氢(D)、碳(C)、氮(N)和硫(S)等各种元素的稳定同位素比值与土壤有机质（OM）的起源和周转有关，因为不完全的（生物）化学反应会使稳定同位素分异。在全球尺度上，降水(D)值与水汽由于蒸发/冷凝相关的同位素分馏作用而到达两极、越过山脉或朝向内陆的过程中所经历的降雨事件的次数有关。由于植物的生物合成依赖于反映降水中(D)值全球分布的当地水源，因此土壤OM中的c键H可能在全球尺度上呈现出(D)值的地理有序分布。土壤有机质的c键(D)值可能局部受到有机质周转的影响。我们的目标是：1)建立一种分析土壤中c -键H (D)值的方法；2)确定全球范围内降水中D值与土壤OM中c -键H之间的关系；3)通过实验室培养和评估不同气候条件下（凋落物到底土）土壤OM中c -键H (D)值的垂直分布，量化分解对土壤OM中c -键D值的影响。该项目在自然地理学中增加了一种新的定量工具，以提高我们对全球尺度上碳封存和循环的理解。

Stable isotope ratios of various elements including H ((D), C, N, and S have been related to origin and turnover of soil organic matter (OM), because incomplete (bio)chemical reactions fractionate stable isotopes. On a global scale, the (D values in precipitation are related to the number of rain events that water vapor undergoes on its way to the poles, across mountains or towards inland because of evaporation/condensation-related isotope fractionation. As plants rely on local water sources that reflect the global distribution of (D values in precipitation for biosynthesis, C-bonded H in soil OM might show a geographically ordered distribution of (D values on a global scale. However, C-bonded (D values in soil OM might locally be modified by organic matter turnover. Our objectives are to 1) establish a method for the analysis of (D values of C-bonded H in soil, 2) determine the relationship between (D values in precipitation and in C-bonded H of soil OM on a global scale, 3) quantify the effect of decomposition on C-bonded (D values in soil OM with laboratory incubations and by assessing the vertical distribution of (D values in C-bonded H of soil OM in different climates (litter to subsoil). The proposed project adds a novel quantitative tool in Physical Geography to improve our understanding of C sequestration and turnover at the global scale.