已知长期的大气氮(N)沉积通过增加陆地生态系统中的可用氮来提高植物生产力。然而,碳过程对陆地生态系统中氮沉积的响应尚不清楚,特别是关于不同的气候区域和生物群落。在这项研究中,我们从218篇发表的关于全球实验N添加的文章中合成了1281个成对观测结果,旨在量化碳过程对N添加的响应及其机制。我们的结果表明,在氮添加处理后,净生态系统生产力(NEP)总体显着提高了31.42%,由于地上净初级生产力的提高(ANPP,16.46%),地下净初级生产力(BNPP,27.74%),和减少的土壤呼吸(Rs,-2.56%),土壤异养呼吸(Rh,-6.24%)。此外,氮添加对NEP的影响因生物群落和气候区域而异。与湿润地区(21.92%)相比,干旱地区(28.67%)氮添加对NEP的积极影响更为明显,主要是由于植被生产力的提高。此外,与草地(31.80%)相比,森林中的N添加显示出更高的NEP(33.95%)。由于呼吸过程的减少。然而,N添加对NEP的积极影响随着实验持续时间的增加而减弱。此外,ANPP和BNPP与N添加率呈凸关系,最佳BNPP添加率超过ANPP。相比之下,Rs对添加率表现出凹形反应。这些发现表明,在未来的大气氮沉积下,陆地生态系统中的碳汇可能会得到增强。特别是在干旱地区和森林生态系统。我们的研究为预测氮沉积如何影响陆地生态系统碳过程提供了见解。
Long-term atmospheric nitrogen (N) deposition has been known to enhance plant productivity by increasing available N in terrestrial ecosystems. However, the response of carbon process to N deposition in terrestrial ecosystems remains unclear, particularly about different climate regions and biomes. In this study, we synthesized 1281 pairwise observations from 218 published articles on experimental N addition globally, aiming to quantify the responses of the carbon process and its mechanisms to N addition. Our results revealed a significant overall increase in net ecosystem productivity (NEP) by 31.42 % following N addition treatment, owing to increased aboveground net primary productivity (ANPP, 16.46 %), belowground net primary productivity (BNPP, 27.74 %), and reduced soil respiration (Rs, -2.56 %), soil heterotrophic respiration (Rh, -6.24 %). Furthermore, the effects of N addition on NEP varied with biomes and climate regions. The positive effect of N addition on NEP was more pronounced in arid regions (28.67 %) compared to humid regions (21.92 %), primarily driven by a higher increase in vegetation productivity. Additionally, N addition exhibited a higher increase in NEP (33.95 %) in forest compared to grassland (31.80 %), resulting from a more reduction in respiratory processes. However, the positive effects of N addition on NEP diminished with increasing experimental duration. Furthermore, ANPP and BNPP displayed a convex relationship with N addition rates, with the optimum BNPP addition rate exceeding that of ANPP. In contrast, Rs exhibited a concave response to addition rates. These findings suggest that carbon sink in terrestrial ecosystems could be enhanced under future atmospheric N deposition, especially in arid regions and forest ecosystems. Our study provided insight for predicting how N deposition influences terrestrial ecosystem carbon process.