Abstract. Land use is recognized to impact soil geochemistry on the centennial to millennial time scale, with implications for the distribution and stability of soil organic carbon (SOC). Juvenile volcanic soils in tropical areas are subject to much faster pedogenesis, with then also possibly a significant mediation by land use on much shorter centennial or even decadal scale. Very scarce observational evidence exists and so such indirect implications of land use on SOC cycling are largely unknown. We here investigated SOC fractions, substrate specific mineralization (SOC or added plant residue), and net priming of SOC in function of forest or agricultural land use on Indonesian volcanic soils. The content of oxalate-extracted Al and exchangeable Ca correlated well with OC associated with sand–sized aggregates. The concomitant near doubling of the proportion of SOC in sand-sized aggregates compared to forest and likewise contrasts in Al and Ca suggest an enhanced formation of Al- (hydr)oxides and liming promoted aggregation and physical occlusion of OC. This was importantly also consistent with a relatively lesser degradability of SOC in the agricultural sites, though the net priming of SOC and degradability of added 13C-labelled ryegrass was not found to depend on land use. We expected that the formation of amorphous Al after conversion of native forest to agriculture would mainly have promoted mineral-association of SOC compared to under pine forest but found no indications for this. Enhanced weathering but improved small scale aggregation of tropical Andosols caused by conversion to agriculture may thus partially counter the otherwise expectable decline of SOC stocks following cultivation. Such indirect land use effects on the SOC balance appeared relevant for correct interpretation and prediction of the long-term C-balance of (agro)ecosystems with soil subject to intense development, like the here studied tropical Andosols.

中文翻译：

---

受土地利用影响的与土壤地球化学相关的热带 Andosol 有机碳质量和可降解性

摘要。土地利用被认为会在百年到千年的时间尺度上影响土壤地球化学，并对土壤有机碳 (SOC) 的分布和稳定性产生影响。热带地区的幼年火山土壤经历了更快的成土过程，然后也可能在更短的百年甚至十年尺度上受到土地利用的显着调节。存在非常稀少的观察证据，因此土地利用对 SOC 循环的这种间接影响在很大程度上是未知的。我们在此研究了 SOC 分数、底物特定矿化（SOC 或添加的植物残留物）以及 SOC 在印度尼西亚火山土壤上的森林或农业用地利用功能中的净启动。草酸盐提取的铝和可交换钙的含量与沙粒大小的骨料相关的 OC 有很好的相关性。与森林相比，沙粒大小的聚集体中 SOC 的比例几乎翻了一番，同样，Al 和 Ca 的对比表明 Al-（氢）氧化物的形成增强，石灰促进了 OC 的聚集和物理闭塞。重要的是，这也与农业场地中相对较低的 SOC 降解性一致，尽管未发现 SOC 的净引发和添加的 13C 标记的黑麦草的降解性取决于土地利用。我们预计，与松树林相比，原生林转变为农业后形成的无定形铝主要促进了 SOC 的矿物结合，但没有发现这方面的迹象。因此，由于转变为农业而增强的风化作用但改善了热带 Andosols 的小规模聚集，因此可以部分抵消种植后 SOC 库存的其他预期下降。这种对土壤有机碳平衡的间接土地利用影响似乎与正确解释和预测（农业）生态系统的长期碳平衡有关，其中土壤受到强烈发展，如这里研究的热带安多溶胶。