Atmospheric nitrogen (N) deposition and anthropogenic phosphorus (P) input simultaneously affect soil respiration (RS), a crucial process that mediates soil carbon (C) cycling. However, the interaction of N deposition and anthropogenic P input on RS, as well as its components—autotrophic respiration (RA) and heterotrophic respiration (RH)—remain largely unexplored. Herein, we conducted an 8-year field experiment with N and P additions in a tropical secondary forest, integrating the vegetation traits, soil physicochemical properties, organic C fractions, and microbial properties, to explore the effects of nutrient inputs and their interactions on RS, RA, and RH. Over eight years, along P input significantly increased RS by 19.2% and RH by 42.1%. These increases were partially mitigated (by 33.2% annually for RS and 58.3% annually for RH) with the addition of N. In contrast, the co-addition of N and P enhanced RA compared to alone N or P addition, suggesting that N deposition mitigated the stimulative effect of P input on RS by reducing RH rather than RA. The structural equation model further revealed that N deposition reduced RH primarily by increasing soil N:P ratio and decreasing both the labile C fraction and fungi biomass. Our findings suggest that prevalent N deposition across low latitudes could have substantially mitigate C emissions from forest soils under anthropogenic P input.

中文翻译：

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氮沉降减轻了磷输入对热带森林土壤呼吸的长期刺激作用


大气中的氮 （N） 沉积和人为磷 （P） 输入同时影响土壤呼吸 （RS），这是介导土壤碳 （C） 循环的关键过程。然而，N 沉积和人为 P 输入对 RS 及其组成部分——自养呼吸 （RA） 和异养呼吸 （RH）——的相互作用在很大程度上仍未得到探索。在此，我们在热带次生林中进行了为期 8 年的氮和磷添加田间试验，整合了植被性状、土壤理化性质、有机碳组分和微生物性质，以探索养分输入及其相互作用对 RS、RA 和 RH 的影响。在八年的时间里，P 输入显著增加了 19.2% 的 RS 和 42.1% 的 RH。添加 N 后，这些增加部分减轻 （RS 每年 33.2%，RH 每年 58.3%）。相比之下，与单独添加 N 或 P 相比，N 和 P 的共添加增强了 RA，表明 N 沉积通过减少 RH 而不是 RA 来减轻 P 输入对 RS 的刺激作用。结构方程模型进一步揭示，氮沉降主要通过增加土壤 N：P 比和降低不稳定的 C 分数和真菌生物量来降低 RH。我们的研究结果表明，在人为磷输入下，低纬度地区普遍存在的氮沉积可以大大减轻森林土壤的碳排放。