Reichenbach Mario, Fiener Peter, Hoyt Alison, Trumbore Susan, Six Johan, Doetterl Sebastian
Institute of Geography, Augsburg University, Augsburg, Germany.
Department of Biogeochemical Processes, Max Planck Institute for Biogeochemistry, Jena, Germany.
Glob Chang Biol. 2023 May;29(9):2591-2607. doi: 10.1111/gcb.16622. Epub 2023 Feb 27.
Soil organic carbon (SOC) dynamics depend on soil properties derived from the geoclimatic conditions under which soils develop and are in many cases modified by land conversion. However, SOC stabilization and the responses of SOC to land use change are not well constrained in deeply weathered tropical soils, which are dominated by less reactive minerals than those in temperate regions. Along a gradient of geochemically distinct soil parent materials, we investigated differences in SOC stocks and SOC (Δ C) turnover time across soil profile depth between montane tropical forest and cropland situated on flat, non-erosive plateau landforms. We show that SOC stocks and soil Δ C patterns do not differ significantly with land use, but that differences in SOC can be explained by the physicochemical properties of soils. More specifically, labile organo-mineral associations in combination with exchangeable base cations were identified as the dominating controls over soil C stocks and turnover. We argue that due to their long weathering history, the investigated tropical soils do not provide enough reactive minerals for the stabilization of C input in either high input (tropical forest) or low-input (cropland) systems. Since these soils exceeded their maximum potential for the mineral related stabilization of SOC, potential positive effects of reforestation on tropical SOC storage are most likely limited to minor differences in topsoil without major impacts on subsoil C stocks. Hence, in deeply weathered soils, increasing C inputs may lead to the accumulation of a larger readily available SOC pool, but does not contribute to long-term SOC stabilization.
土壤有机碳（SOC）动态取决于土壤形成时的地球气候条件所衍生的土壤性质，并且在许多情况下会因土地利用变化而改变。然而，在深度风化的热带土壤中，SOC的稳定以及SOC对土地利用变化的响应并未得到很好的限制，这些土壤中活性较低的矿物比温带地区的土壤更为常见。沿着地球化学性质不同的土壤母质梯度，我们研究了位于平坦、无侵蚀高原地貌上的山地热带森林和农田之间，土壤剖面深度上SOC储量和SOC（ΔC）周转时间的差异。我们发现，SOC储量和土壤ΔC模式在土地利用方式上没有显著差异，但SOC的差异可以用土壤的物理化学性质来解释。更具体地说，不稳定的有机-矿物结合体与可交换碱金属阳离子被确定为控制土壤碳储量和周转的主要因素。我们认为，由于其漫长的风化历史，所研究的热带土壤无论是在高输入（热带森林）还是低输入（农田）系统中，都没有提供足够的活性矿物来稳定碳输入。由于这些土壤已经超过了与矿物相关的SOC稳定的最大潜力，重新造林对热带SOC储存的潜在积极影响很可能仅限于表土的微小差异，而对亚表层土壤碳储量没有重大影响。因此，在深度风化的土壤中，增加碳输入可能会导致更大的易利用SOC库的积累，但对长期的SOC稳定没有贡献。
