Tropical forests account for a large portion of the Earth's terrestrial carbon pool. However, rapid deforestation threatens the stability of this carbon. We examine radiocarbon (Δ¹⁴C) and stable carbon (δ¹³C) isotopes of soil organic matter to provide insight into rates of carbon turnover, inputs, and losses of pasture‐derived (C4) versus forest or oil palm‐derived (C3) carbon. Data are presented for natural lowland forests on mineral soil converted to pastures in Peru and to oil palm plantations in Peru, Indonesia, and Cameroon. We additionally examine plots of secondary forests following agricultural use. There were large losses in carbon stocks under both pasture and oil palms. In the plots converted to pasture, our data indicate a preferential loss of relatively young carbon, and a greater loss of forest‐derived carbon than replacement with pasture‐derived carbon. Natural forests converted directly to oil palm plantations sustained losses in carbon, but Δ¹⁴C values suggest that the soil may retain a sufficient amount of newly acquired carbon to offset initial losses of young carbon. Furthermore, replacement of pastures with oil palm plantations facilitates the accumulation of young carbon, which may lead to a gradual increase in carbon stocks. The sites examined here are representative of the biophysical characteristics in roughly half of the humid tropics, suggesting that these findings may be applicable to a large area of similarly managed mineral soils in lowland tropical forests.

中文翻译：

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从放射性碳推断的热带低地土地利用变化和转化为油棕种植后的土壤碳动态

热带森林占地球陆地碳库的很大一部分。但是，快速的森林砍伐威胁了这种碳的稳定性。我们检查放射性碳（Δ ¹⁴ C）和稳定的碳（δ ¹³C）土壤有机物的同位素，以提供有关碳转化率​​，输入量以及草场（C4）与森林或油棕树（C3）碳损失的比率的信息。数据显示了秘鲁转换为牧场，秘鲁，印度尼西亚和喀麦隆的油棕种植园的天然低地森林的矿物土壤。我们还研究了农业利用后的次生林地块。牧场和油棕下的碳储量大量减少。在转换为牧场的地块中，我们的数据表明相对于用牧草碳替代，相对年轻的碳优先流失，而森林碳的损失更大。天然森林直接转化为油棕榈种植园持续的碳损失，但Δ ¹⁴C值表明土壤可以保留足够数量的新获得的碳，以抵消年轻碳的初始损失。此外，用油棕种植园代替草场有利于年轻碳的积累，这可能导致碳储量的逐渐增加。此处检查的地点代表了大约一半湿热带地区的生物物理特征，这表明这些发现可能适用于低地热带森林中大面积类似管理的矿物土壤。