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，并稳定在微团聚体中，但微团聚体结构对SOM储存和周转时间的影响一直没有得到研究人员的关注。该项目旨在结合电子探针分析测绘技术(EPMA)和三维激光消融同位素比值监测(LA-ICPMS和LA-IRMS)来阐明SOM的时空模式、其同位素特征以及尺寸为4-20？m的微团聚体中邻近的其他元素。随后使用模式识别和地质统计学工具进行的数据评估将使我们能够回答以下问题：(1)不同年龄和年限的微团聚体(微观实验、地形序列、年代序列)中SOM的空间模式在多大程度上遵循确定性模式，(Ii)土壤有机质在微团聚体中的周转时间和生物可获得性在多大程度上影响C和N的空间异质性，以及(Iii)土壤铁氧化物和粘土矿物如何控制有机质在微团聚体中的积累和周转。我们假设，微团聚体年龄越大，解释土壤有机质动态的随机过程就越不相关，从而为这些微结构在营养物质的生物地球化学循环和C周转中所起的作用提供了线索。

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.