Centre for Ecology & Hydrology, Environment Centre Wales, Bangor, Gwynedd, UK.
Centre for Ecology & Hydrology, Wallingford, Oxfordshire, UK.
Glob Chang Biol. 2019 Dec;25(12):3996-4007. doi: 10.1111/gcb.14787. Epub 2019 Aug 28.
Soil organic matter (SOM) is an indicator of sustainable land management as stated in the global indicator framework of the United Nations Sustainable Development Goals (SDG Indicator 15.3.1). Improved forecasting of future changes in SOM is needed to support the development of more sustainable land management under a changing climate. Current models fail to reproduce historical trends in SOM both within and during transition between ecosystems. More realistic spatio-temporal SOM dynamics require inclusion of the recent paradigm shift from SOM recalcitrance as an 'intrinsic property' to SOM persistence as an 'ecosystem interaction'. We present a soil profile, or pedon-explicit, ecosystem-scale framework for data and models of SOM distribution and dynamics which can better represent land use transitions. Ecosystem-scale drivers are integrated with pedon-scale processes in two zones of influence. In the upper vegetation zone, SOM is affected primarily by plant inputs (above- and belowground), climate, microbial activity and physical aggregation and is prone to destabilization. In the lower mineral matrix zone, SOM inputs from the vegetation zone are controlled primarily by mineral phase and chemical interactions, resulting in more favourable conditions for SOM persistence. Vegetation zone boundary conditions vary spatially at landscape scales (vegetation cover) and temporally at decadal scales (climate). Mineral matrix zone boundary conditions vary spatially at landscape scales (geology, topography) but change only slowly. The thicknesses of the two zones and their transport connectivity are dynamic and affected by plant cover, land use practices, climate and feedbacks from current SOM stock in each layer. Using this framework, we identify several areas where greater knowledge is needed to advance the emerging paradigm of SOM dynamics-improved representation of plant-derived carbon inputs, contributions of soil biota to SOM storage and effect of dynamic soil structure on SOM storage-and how this can be combined with robust and efficient soil monitoring.
土壤有机质（SOM）是可持续土地管理的指标，这在联合国可持续发展目标（SDG 指标 15.3.1）的全球指标框架中有所说明。需要改进对未来 SOM 变化的预测，以支持在气候变化下发展更可持续的土地管理。当前的模型无法重现 SOM 在生态系统内部和之间转变期间的历史趋势。更现实的时空 SOM 动态需要包括最近从 SOM 抗降解性作为“内在特性”到 SOM 持久性作为“生态系统相互作用”的范式转变。我们提出了一个土壤剖面或个体显型的生态系统尺度框架，用于 SOM 分布和动态的数据和模型，以更好地表示土地利用的转变。生态系统尺度的驱动因素与个体尺度的过程在两个影响区域中结合在一起。在植被上层，SOM 主要受到植物输入（地上和地下）、气候、微生物活动和物理团聚体的影响，容易失稳。在下层矿物质基质区，植被区的 SOM 输入主要受到矿物质相和化学相互作用的控制，导致更有利于 SOM 持久性的条件。植被区边界条件在景观尺度上（植被覆盖）空间变化，在十年尺度上（气候）时间变化。矿物质基质区边界条件在景观尺度上（地质、地形）空间变化，但变化缓慢。两个区域的厚度及其运输连通性是动态的，受到植被覆盖、土地利用实践、气候以及每层当前 SOM 存量的反馈的影响。使用这个框架，我们确定了几个需要更多知识才能推进 SOM 动态新兴范式的领域，包括改进植物衍生碳输入的表示、土壤生物群对 SOM 储存的贡献以及动态土壤结构对 SOM 储存的影响，以及如何将其与强大而有效的土壤监测相结合。
