Evolution of the transport properties of soil aggregates and their relationship with soil organic carbon following land use changes
Evolution of the transport properties of soil aggregates and their relationship with soil organic carbon following land use changes
复制标题
DOI：
10.1016/j.still.2021.105226
复制
发表时间：
2022-01
影响因子：
6.5
通讯作者：
Feng Wang;Xiaoxian Zhang;A. Neal;J. Crawford;S. Mooney;A. Bacq-Labreuil
中科院分区：
文献类型：
--
作者：
Feng Wang;Xiaoxian Zhang;A. Neal;J. Crawford;S. Mooney;A. Bacq-Labreuil
团聚体是描述土壤结构变化对土壤物理和生物地球化学过程影响的功能单位。孵化和实地实验都表明，改变农业实践可以在几天内重塑群落内部结构，但大多数此类数据都是从单一时间点获得的，因此不可能将这种变化解释为仅仅是一个时间过渡，或者是随着管理变化而进化的群落的新平衡。了解这一点是必不可少的，因为团聚体内部结构及其运输基质的能力调节了土壤碳和养分循环中涉及的所有生物地球化学过程。本文利用2008年英国洛桑研究所（Rothamsted Research）启动的一项回归实验中收集的土壤样本进行了调查，该实验中，自20世纪50年代以来一直休耕的部分地块在2008年被转化为小麦或草。利用1.5µm体素的x射线计算机断层扫描图像，研究了土壤中团聚体的迁移特性随时间的演变及其与土壤有机碳（SOC）的关系。我们还评估了转换后孔隙连通性的发展。结果表明，团聚体的转运能力比孔隙度更好地解释了有机碳的变化，并且直到转化后第6年，连接孔的孔隙度及其转运基质的能力才出现明显的变化。转换10年后，连通孔隙的孔隙度和体积扩散系数仍未见平稳变化。此外，还草显著改变了团聚体内部孔隙几何形状，其团聚体的体积扩散系数随孔隙度的变化趋势与裸休耕和耕地处理有显著差异。所有这些都表明，转化后的团聚体内部重新配置是一个缓慢的过程，孔隙空间运输基质的能力比它们提供的土壤有机碳稳定的栖息地更重要。
Aggregates are functional units to describe the impact of soil structural changes on physical and biogeochemical processes in soil. Both incubation and field experiments have shown that changing agricultural practices could reshape the intra-aggregate structure in a matter of days, but most such data were obtained from a single time-point and it is hence impossible to interpret that such a change was just a temporal transition or the new equilibria towards which the aggregates had evolved following the management changes. Understanding this is indispensable as intra-aggregate structure and its ability to transport substrates modulate all biogeochemical processes involved in soil carbon and nutrient cycle. This paper investigates this using soil samples archived from a reversion experiment initiated in 2008 at Rothamsted Research (UK), where parts of a plot that had been fallow since the 1950 s were converted to wheat or grass in 2008. We used X-ray Computed Tomography images, acquired at voxel size 1.5 µm, of aggregates in the archived soils to investigate the evolution of transport property of the aggregates over time, as well as its relationship with soil organic carbon (SOC). We also evaluated the development of pore connectedness following the conversion. The results show that the transport ability of the aggregates explains the SOC change much better than the porosity, and that noticeable changes in porosity of the connected pores and their ability to transport substrates did not emerge until the sixth year after the conversion. Ten years after the conversion, there was still no sign of the porosity of the connected pores and the bulk diffusion coefficient to plateau. In addition, we found the conversion to grass changed the intra-aggregate pore geometry significantly in that the bulk diffusion coefficients of their aggregates trends with their porosities in a way differing significantly from those for the bare fallow and arable treatments. All these suggest that the intra-aggregate reconfiguration following the conversion is a slow process, and that the ability of pore space to transport substrates is more important than the habitat they provide in SOC stabilisation.