Aims

Increased nitrification risks accelerating soil acidification under land-use change from tropical forest to cropland or plantation, but acidity might be neutralized by net mineralization of soil organic matter (SOM) that has accumulated under the former fallow vegetation. We aim to analyze key drivers of soil acidification and acid neutralization under different crops and fallow vegetation.

Methods

We compared 30 year changes in soil C stocks, pH, and exchangeable Al under different land-uses (primary dipterocarp forest, Macaranga forest, Imperata grassland, Imperata grassland converted to Acacia plantation, Imperata grassland converted to oil palm plantation) in Indonesia and identified the major drivers of acidification using proton budgets in soil.

Results

Nitrification is major driver of acidification in soil profiles under N-fixing Acacia or fertilized oil palm plantation. Protons generated by product removal and nitrification in oil palm plantation are neutralized partly by fertilizer and mineralization of the native SOM that has formerly accumulated under grassland. The remaining acidity results in accumulation of soil exchangeable Al. The SOM storage under short-term (< 10 yr) grass or long-term (> 10 yr) Macaranga forest increases without intensive acidification, while long-term Acacia plantation maximizes both SOM storage and acidification.

Conclusion

Magnitude of soil acidification is regulated largely by the balance between proton generation by nitrification of fertilized N and biologically-fixed N and proton consumption by net mineralization of the native SOM that has formerly accumulated under grass fallow. SOM accumulation under Imperata grassland or Macaranga forest could mitigate soil acidification in Acacia or oil palm plantation.

中文翻译：

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印度尼西亚不同土地利用方式下土壤酸化率的比较

目的

在从热带森林到农田或人工林的土地利用变化下，增加的硝化风险有加速土壤酸化的风险，但酸度可能会被以前的休耕植被下积​​累的土壤有机质（SOM）的净矿化作用所中和。我们旨在分析不同作物和休闲植被下土壤酸化和酸中和的关键驱动因素。

方法

我们比较了印度尼西亚不同土地利用下的30年土壤碳储量，pH值和可交换铝的变化（原生龙脑香林，Macaranga森林，Imperata草原，Imperata草原转化为金合欢人工林，Imperata草原转化为油棕人工林）。使用土壤中的质子预算来酸化的主要驱动力。

结果

在固氮的金合欢树或施肥的油棕人工林下，硝化作用是土壤剖面酸化的主要驱动力。油棕种植园中产品去除和硝化产生的质子会部分地被化肥和矿化的天然SOM所中和。剩余的酸度导致土壤可交换铝的积累。在短期（<10年）草或长期（> 10年）Macaranga森林下，SOM的存储量会增加，而不会进行强烈的酸化作用，而相思树的长期种植会最大化SOM的存储量和酸化程度。

结论

土壤酸化的强度主要受制于受精氮和生物固氮硝化产生的质子与原先在草场下积累的天然SOM的净矿化作用所产生的质子消耗之间的平衡。Imperata草原或Macaranga森林下的SOM积累可减轻相思树或油棕种植园中的土壤酸化。