Both temperature and nutrient availability have essential roles in regulating the decomposition of soil carbon (C) and nitrogen (N), the main controls on organic matter accumulation in forest ecosystems. However, there is a lack of information about how N deposition and phosphorus (P) additions might impact soil C and N decomposition rates in subtropical forests under climate warming. We measured soil organic C and N mineralisation rates and corresponding exoenzyme activities in a subtropical forest soil that had received N and/or P additions for six years in experimental conditions at a range of temperatures between 10 and 40°C. Our results showed that soil organic C and N decomposition rates were positively correlated with the activities of their corresponding enzymes, which suggests that the extracellular enzyme activities could be the main influence on soil organic matter (SOM) decomposition rates. N additions had a significant positive effect on soil organic C mineralisation and enhanced oxidase and hydrolase activities. P additions had little effect on soil organic C and N decomposition rates. These results challenge the assumptions that soil microorganisms are N-rich and P availability restricts organic matter decomposition, and provides additional evidence that N, not P, regulates organic matter decomposition in subtropical forests. While N additions significantly influenced the soil C and N decomposition rates, they had little effect on their sensitivity to temperature. In contrast, P additions had a significant effect on the temperature sensitivities of SOM decomposition and the βG and NAG V_max. Overall, our results show that SOM decomposition is vulnerable to both N and P additions, and both should be considered when predicting how SOM decomposition and C cycling might change under warming.

中文翻译：

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变暖导致亚热带针叶林氮肥和磷肥处理土壤中 SOM 分解的变异性

温度和养分可用性在调节土壤碳 (C) 和氮 (N) 的分解方面具有重要作用，土壤碳 (C) 和氮 (N) 是森林生态系统中有机质积累的主要控制因素。然而，关于气候变暖下亚热带森林中 N 沉降和磷 (P) 添加可能如何影响土壤 C 和 N 分解速率的信息还很缺乏。我们测量了亚热带森林土壤中的土壤有机碳和氮矿化率以及相应的胞外酶活性，该土壤在 10 至 40°C 的温度范围内的实验条件下接受了六年的 N 和/或 P 添加。我们的结果表明，土壤有机碳和氮分解速率与其相应酶的活性呈正相关，这表明细胞外酶活性可能是影响土壤有机质 (SOM) 分解速率的主要因素。N 添加对土壤有机碳矿化和增强氧化酶和水解酶活性具有显着的积极影响。添加磷对土壤有机碳和氮的分解速率影响不大。这些结果挑战了土壤微生物富含 N 和 P 可用性限制有机物分解的假设，并提供了额外的证据表明 N，而不是 P，调节亚热带森林中的有机物分解。虽然添加 N 会显着影响土壤 C 和 N 的分解速率，但它们对温度的敏感性几乎没有影响。相反，P 添加对 SOM 分解的温度敏感性以及 βG 和 NAG V 有显着影响_最大值_ 总体而言，我们的结果表明，SOM 分解容易受到 N 和 P 添加的影响，在预测 SOM 分解和 C 循环在变暖条件下可能发生的变化时应考虑这两者。