Soil element patterns and carbon turnover at the micro-scale (20-250 µm)

土壤有机质（SOM）在不同尺度上分布不均匀，并稳定在微团聚体中，但微团聚体结构对SOM储存和周转时间的作用一直困扰着研究人员。该项目旨在结合电子探针分析绘图技术（EPMA）和三维激光烧蚀同位素比监测（LA-ICP-MS和LA-IRMS），以阐明SOM的时空模式，其同位素特征和微聚集体中的相邻其他元素，尺寸小至4-20 μ m。利用模式识别和地统计学方法对数据进行评价，可以回答以下问题：（1）不同年龄和种源的微团聚体中有机质的空间格局（微观实验，地形序列，时间序列）遵循一个确定性的模式，ii）在何种程度上周转时间和生物可及性的有机质微团聚体影响的空间异质性的C和N，以及（iii）成土氧化铁和粘土矿物如何控制微团聚体热点中SOM的积累和周转。我们假设，年龄越大的微团聚体，相关的随机过程来解释SOM的动态，从而提供了一个线索，这些微结构的营养物质和碳周转的地球化学循环的作用。

Soil organic matter (SOM) is heterogeneously distributed at different scales and stabilized in microaggregates, but the role of microaggregates¿ architecture for SOM storage and turnover time has eluded researchers. This project aims at combining electron microprobe analyses mapping techniques (EPMA) and a three dimensional laser-ablation isotope ratio monitoring (LA-ICP-MS and LA-IRMS) to elucidate the spatio-temporal patterns of SOM, its isotopic signature and adjacent other elements in microaggregates down to a size of 4-20 ¿m. The subsequent data evaluation using pattern recognition and geostatistical tools will allow us to answer the following questions (i) to which extent does the spatial pattern of SOM within microaggregates of different age and provenience (microcosm experiment, toposequence, chronosequence) follow a deterministic pattern, ii) to which extent does turnover time and bioaccessibility of SOM within microaggregates affect spatial heterogeneity of C and N, and (iii) how do pedogenic iron oxides and clay minerals control the accumulation and turnover of SOM in microaggregates¿ hot spots. We hypothesize that the older the microaggregates are, the less relevant are stochastic processes to explain the dynamics of SOM, thus providing a clue to the role of these microstructures for the biogeochemical cycling of nutrients and C turnover.