Nitrogen (N) and phosphorus (P) deposition have largely affected soil respiration (Rs) in forest ecosystems. However, few studies have explored how N and P individually or in combination to influence Rs and its components (autotrophic respiration, Ra; heterotrophic respiration, Rh), especially in highly P-limited subtropical forests. To address this question, we conducted a field manipulation experiment with N and/or P addition in a 50-year-old subtropical secondary forest. We found that N addition on average reduced Rs, Ra, and Rh by 15.2%, 15%, and 11.7%, respectively during 2-year field study. P addition had an inconsistent effect on Ra, with Ra increasing by 50.5% in the first year but reducing by 26.6% in the second year. Moreover, P addition on average decreased Rh by 8.9%–30.9% and Rs by 6.7%–15.6% across 2 years. In contrast, N and P co-addition on average increased Rs, Ra, and Rh by 1.9%, 7.9%, and 2.1% during the experimental period. Though Rs and Rh were significantly correlated with soil temperature, their temperature sensitivities were not significantly changed by fertilization. Ra was predominantly regulated by soil nitrogen availability (NH4+ and NO3−), soil dissolved organic carbon (DOC), and enzyme activities, while the variation in Rh was mainly attributable to changes in soil microbial community composition and soil β-D-Cellubiosidase (CB) and β-Xylosidase (XYL) activities. Our findings highlight the contrasting responses of Rs and its components to N or P addition against N and P co-addition, which should be differentially considered in biogeochemical models in order to improve prediction of forest carbon dynamics in the context of N and P enrichment in terrestrial ecosystems.

中文翻译：

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亚热带次生林土壤呼吸及其组分对氮磷添加的不同响应

氮 (N) 和磷 (P) 沉积在很大程度上影响了森林生态系统中的土壤呼吸 (Rs)。然而，很少有研究探讨 N 和 P 单独或组合如何影响 Rs 及其成分（自养呼吸，Ra；异养呼吸，Rh），尤其是在高度限磷的亚热带森林中。为了解决这个问题，我们在 50 年历史的亚热带次生林中进行了添加 N 和/或 P 的田间操作实验。我们发现，在 2 年的实地研究中，添加 N 平均使 Rs、Ra 和 Rh 分别降低了 15.2%、15% 和 11.7%。P添加对Ra的影响不一致，第一年Ra增加50.5%，第二年减少26.6%。此外，在 2 年内，P 添加平均使 Rh 降低了 8.9%–30.9%，Rs 降低了 6.7%–15.6%。相比之下，在实验期间，N 和 P 的共同添加平均使 Rs、Ra 和 Rh 增加了 1.9%、7.9% 和 2.1%。尽管Rs和Rh与土壤温度显着相关，但它们的温度敏感性并未因施肥而发生显着变化。Ra主要受土壤氮有效性（NH4+和NO3-）、土壤溶解有机碳（DOC）和酶活性的调节，而Rh的变化主要归因于土壤微生物群落组成和土壤β-D-纤维苷酶的变化。 CB) 和 β-木糖苷酶 (XYL) 活性。我们的发现突出了 Rs 及其成分对 N 或 P 添加与 N 和 P 共添加的对比反应，