Nonlinear responses of ecosystem carbon fluxes and water-use efficiency to nitrogen addition in Inner Mongolia grassland
Nonlinear responses of ecosystem carbon fluxes and water-use efficiency to nitrogen addition in Inner Mongolia grassland
复制标题
内蒙古草原生态系统碳通量和水分利用效率对氮添加的非线性响应
DOI：
10.1111/1365-2435.12513
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发表时间：
2016
影响因子：
5.2
通讯作者：
Han Xingguo
中科院分区：
文献类型：
--
作者：
Tian Dashuan;Niu Shuli;Pan Qingmin;Ren Tingting;Chen Shiping;Bai Yongfei;Han Xingguo
氮沉降是一个连续的过程，可能以非线性的方式影响生态系统的碳通量和水通量。通过对内蒙古草原12年6个水平的氮素添加试验，研究了不同氮素水平下，生态系统净碳交换（NEE）、生态系统总生产力（GEP）、生态系统呼吸（ER）、碳通量（CO2）、碳通量（随着施氮量的增加，三种作物的蒸散量均呈非线性变化，而蒸散量变化不显著。结果表明，氮素对生态系统水分利用效率（EWUE）的响应与NEE相似，氮素对生态系统碳通量的影响主要受生长季不同阶段降水分布的影响，并主要受生物量生产的影响，而不是土壤温度和土壤湿度的影响。这应该被纳入全球碳循环模型，以更好地预测未来的碳平衡。我们的研究结果也有影响，施肥在恢复退化的草地，N除了可以促进生物量的生产和生态系统C的吸收，而无需额外的水蒸散，但也改变生态系统的组成。
Nitrogen (N) deposition is a continuous process and likely to affect ecosystem carbon (C) and water fluxes in a nonlinear way. However, experimental evidence is still lacking because most previous studies on these impacts usually used two discrete levels of N treatment.By a 12‐year, 6‐level N addition experiment in Inner Mongolia grassland, we found that the responses of C fluxes, including net ecosystem carbon exchange (NEE), gross ecosystem productivity (GEP), ecosystem respiration (ER), all exhibited nonlinear patterns with increasing N addition rate while that of evapotranspiration did not significantly change. As a result, the response of ecosystem water‐use efficiency (EWUE) followed a similar pattern with NEE.These N‐induced changes in C fluxes were greatly affected by the distribution of precipitation among different stages of growing seasons and mainly driven by the alterations in biomass production rather than soil temperature and soil moisture.This study highlights the importance of the nonlinearity of N addition impacts on ecosystem C fluxes, which should be incorporated into the global‐C‐cycling models for better predicting future C balance. Our results also have implications for the use of fertilization in restoring the degraded grasslands given that N addition can promote biomass production and ecosystem C uptake without additional water evapotranspiration but also change ecosystem composition.