Plant community temporal stability in response to nitrogen addition among different degraded grasslands.
Plant community temporal stability in response to nitrogen addition among different degraded grasslands.
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DOI：
10.1016/j.scitotenv.2020.138886
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发表时间：
2020-04
期刊：
影响因子：
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通讯作者：
Mei Zhou;Qiang Yang;Hongjin Zhang;Xiaodong Yao;Wenjing Zeng;Wei Wang
中科院分区：
文献类型：
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作者：
Mei Zhou;Qiang Yang;Hongjin Zhang;Xiaodong Yao;Wenjing Zeng;Wei Wang
大气氮(N)沉积通常被认为降低植物群落的时间稳定性。然而，目前尚不清楚群落对氮沉降的时间稳定性响应是否随干扰机制的不同而不同，例如不同退化程度的草原之间。我们在中国北部四个不同退化状态(未退化、中度退化、重度退化和极度退化草地)的草地上进行了为期4年的6个氮素添加水平的田间试验。我们考察了群落时间稳定性(以群落生物量平均值与其标准差之比表示)对氮素添加和重要调节因子的响应。异步性被计算为1和同步性之间的差值(量化为群落生物量的方差与物种生物量标准差之和的平方之比)。最有趣的结果是，在未加氮的四种草地中，中、重度退化草地的群落时间稳定性相对较高。这归因于优势物种组成的变化，而不是物种多样性的变化。除中度退化草地外，几乎所有站点的群落时间稳定性都不受施氮量的显著影响。中度退化草地群落时间稳定性对施氮量的响应是非线性的，低施氮量(10和20 mg·N/m−2yr−1)促进群落时间稳定性，高施氮量(30~50 mg·N·−·2yr−1)降低群落时间稳定性。此外，未退化和中度退化草地群落的时间稳定性主要受物种异步性的影响。而在严重退化和极度退化草地上，群落时间稳定性主要受物种丰富度和优势种稳定性的影响。这些结果突出了草地退化在群落时间稳定性对氮沉降响应中的重要性，为退化草地的管理和恢复提供了科学依据。
Atmospheric nitrogen (N) deposition is generally believed to decrease plant community temporal stability. However, it remains unclear whether the responses of community temporal stability to N deposition vary with disturbance regimes, such as among different grasslands with degrees of degradation. We established a 4-year field experiment with six N addition levels on four grassland sites in northern China with varying degradation statuses (non-degraded, moderately, severely and extremely degraded grasslands). We examined the response of community temporal stability (quantified as the ratio of the mean of community biomass to its standard deviation) to N addition and important regulating factors. Asynchrony was calculated as the difference between one and synchrony (quantified as the ratio of the variance of community biomass to the square of the sum of the standard deviation of species biomass). The most interesting result we found was that community temporal stability of the moderately and severely degraded grasslands was relatively higher among the four grasslands without N addition. This was attributed to shifts in dominant species composition rather than species diversity. Community temporal stability of nearly all sites were not significantly affected by N addition except the moderately degraded grassland. Community temporal stability of the moderately degraded grassland responded to N addition non-linearly, being promoted by low N addition levels (10 and 20 g N m−2yr−1) and decreased by high N addition levels (30–50 g N m−2yr−1). Furthermore, community temporal stability of the non-degraded and moderately degraded grasslands was mainly driven by species asynchrony. Whereas, in the severely and extremely degraded grasslands, community temporal stability was mainly regulated by species richness and dominant species stability, respectively. These findings highlight the importance of grassland degradation in the response of community temporal stability to N deposition and provide scientific support for the management and restoration of degraded grasslands.