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Global pattern and drivers of nitrogen saturation threshold of grassland productivity
Functional Ecology ( IF 4.6 ) Pub Date : 2020-07-15 , DOI: 10.1111/1365-2435.13622 Yunfeng Peng 1 , Han Y. H. Chen 2 , Yuanhe Yang 1, 3
中文翻译：
草地生产力氮饱和阈值的全球格局及其驱动因素
更新日期：2020-07-15
Functional Ecology ( IF 4.6 ) Pub Date : 2020-07-15 , DOI: 10.1111/1365-2435.13622 Yunfeng Peng 1 , Han Y. H. Chen 2 , Yuanhe Yang 1, 3
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- Ecosystem productivity usually exhibits first increase and then saturated response to increasing nitrogen (N) additions, yet the broad‐scale pattern and potential drivers of the N saturation threshold are little investigated.
- By synthesizing N addition experiments with at least four N‐input levels from the global grasslands, we applied the quadratic‐plus‐plateau model to fit the above‐ground net primary productivity (ANPP)–N rate relationship, and estimated the saturation threshold for N rate (critical N rate, NCR) and ANPP (maximum ANPP, ANPPmax) from the inflection point where ANPP no longer statistically increased with N rate for individual experiments. Based on these estimations, we investigated the spatial pattern and driving factors of NCR and ANPPmax.
- The mean NCR and ANPPmax were 15.0 and 477.0 g m−2 year−1, respectively, but varied substantially among single‐site experiments. Management strategies (e.g. biomass harvest, different N forms and addition frequencies) minimally influenced both parameters. Structural equation models demonstrated that the spatial differences in NCR and ANPPmax were mainly explained by aridity index, and soil carbon (C)/N ratio also predicted the variation in NCR.
- Given that grasslands are important not only for the trend and variability of the land C sink but also for the maintenance of pasture yield, the pattern and controls of NCR and ANPPmax, as revealed by the current study, are crucial for constructing robust predictions of C sink capacity and improving N fertilizer management in grasslands.
中文翻译：
草地生产力氮饱和阈值的全球格局及其驱动因素
- 生态系统生产力通常表现为先增加，然后对增加的氮（N）产生饱和响应，但是对氮饱和阈值的广泛模式和潜在驱动因素的研究很少。
- 通过综合来自全球草地的至少四个N输入水平的N添加实验，我们应用了二次加高原模型来拟合地上净初级生产力（ANPP）-N速率关系，并估算了饱和阈值从拐点开始的N速率（临界N速率，N CR）和ANPP（最大ANPP，ANPP max）从各个拐点开始，ANPP不再随N速率统计地增加。基于这些估计，我们研究了N CR和ANPP max的空间格局和驱动因素。
- 平均N CR和ANPP max分别为15.0和477.0 g m - 2 年-1，但在单点实验之间差异很大。管理策略（例如生物量收获，不同的氮形态和添加频率）对这两个参数的影响最小。结构方程模型表明，N CR和ANPP max的空间差异主要由干旱指数解释，土壤碳（C）/ N比也可预测N CR的变化。
- 鉴于草地不仅对于土地碳汇的趋势和变化非常重要，而且对于维持牧草产量也很重要，所以本研究揭示的N CR和ANPP max的模式和控制对构建可靠的预测至关重要碳库容量的改善和改善草地上的氮肥管理。
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