Variations in the nitrogen saturation threshold of soil respiration in grassland ecosystems
Variations in the nitrogen saturation threshold of soil respiration in grassland ecosystems
复制标题
草地生态系统土壤呼吸氮饱和阈值的变化
DOI：
10.1007/s10533-020-00661-y
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发表时间：
2020
期刊：
影响因子：
4
通讯作者：
Jin-Sheng He
中科院分区：
文献类型：
--
作者：
Chao Wang;Fei Ren;Xuhui Zhou;Wenhong Ma;Cunzhu Liang;Jinzhou Wang;Jianwei Cheng;Huakun Zhou;Jin-Sheng He
在过去的一个世纪里，人类活动显著增加了氮(N)的沉积，这显著影响了生态系统的过程，并有可能在未来导致N的饱和。土壤呼吸(Rs)是碳(C)循环的重要组成部分，N沉积的持续增加可能导致土壤呼吸的非线性响应。然而，对土壤呼吸的N饱和阈值知之甚少。在这项研究中，我们在中国北部的四个草地类型和四个氮素添加水平上进行了协调试验，以探索Rs饱和阈值的规律。结果表明，草地生态系统普遍存在Rs饱和阈值，以响应N的添加梯度。高寒草甸、草甸草原、典型草原和荒漠草原的氮素饱和阈值分别为100kgN/ha−1yr−1、50kgN/ha−1yr−1和25kgN/hm2 1yr 1，但随草地类型的不同而变化较大。自养呼吸(Ra)和异养呼吸(Rh)对氮素添加梯度的响应不同。Ra最初增加，并以50亿kg/N/ha−1yr−1的速度饱和，此后下降。相反，添加N后，Rh单调下降。结构方程模型进一步证实，氮素添加梯度对Rs的影响主要由地下生物量的非线性响应决定。有趣的是，汇编的全球数据集显示，Rs的N饱和阈值随着降雨量和土壤水分的增加而增加。这些结果表明，未来氮沉降对Rs和Ra的刺激作用可能会随着氮沉降的增加而减弱，特别是在干旱草原生态系统中。
Over the last century, anthropogenic activities have increased nitrogen (N) deposition considerably, which significantly affects ecosystem processes and has the potential to induce N saturation in the future. The continuous increase in N deposition may cause a non-linear response in soil respiration (Rs), an important component of carbon (C) cycling. However, little is known about N saturation threshold of soil respiration. In this study, we conducted coordinated experiments in four grassland types across northern China with four N addition levels to explore patterns in the Rs saturation threshold. Our results showed that an Rs saturation threshold generally exists in grassland ecosystems in response to N addition gradients. The N saturation threshold of Rs occurred at an average rate of 50 kg N ha−1yr−1, but varied widely with grassland type; the N saturation threshold occurred at rates of 100, 50, 50, and 25 kg N ha−1yr−1in the alpine meadow, meadow steppe, typical steppe, and desert steppe, respectively. Autotrophic respiration (Ra) and heterotrophic respiration (Rh) responded to N addition gradients differently. Ra increased initially and became saturated at a rate of 50 kg N ha−1yr−1and declined thereafter. In contrast, Rh decreased monotonically after N addition. Structural equation models further confirmed that the effects of N addition gradients on Rs were primarily determined by the non-linear response of belowground biomass. Interestingly, the compiled global dataset showed that the N saturation threshold of Rs increased with precipitation and soil moisture. These findings indicate that the stimulating effect of N deposition on Rs and Ra might diminish with increasing N deposition in the future, especially in dry grassland ecosystems.