Long-term Research Station of Alpine Forest Ecosystems, Provincial Key Laboratory of Ecological Forestry Engineering, Institute of Ecology and Forestry, Sichuan Agricultural University, 211 Huimin Road, Wenjiang District, Chengdu 611130, China.
Long-term Research Station of Alpine Forest Ecosystems, Provincial Key Laboratory of Ecological Forestry Engineering, Institute of Ecology and Forestry, Sichuan Agricultural University, 211 Huimin Road, Wenjiang District, Chengdu 611130, China.
Environ Pollut. 2018 Oct;241:740-749. doi: 10.1016/j.envpol.2018.06.018. Epub 2018 Jun 8.
To test the hypothesis that nutrient-limited conditions can determine the responses of nitrogen (N) and phosphorus (P) stoichiometry to N addition, a meta-analysis was conducted to identify the different responses of foliar N and P concentrations and N-to-P ratios to N addition under N limitation, N and P co-limitation and P limitation. N addition increased the foliar N-to-P ratios and N concentrations by 46.2% and 30.2%, respectively, under N limitation, by 18.7% and 19.7% under N and P co-limitation, and by 4.7% and 12.9% under P limitation. However, different responses of foliar P concentrations to N addition were observed under different nutrient limitations, and negative, positive, and neutral effects on P concentrations were observed under N limitation, P limitation and N and P co-limitation, respectively. Generally, the effects of N addition on N-to-P ratios and N concentrations in herbaceous plants were dramatically larger than those in woody plants (with the exception of the N-to-P ratio under N limitation), but the opposite situation was true for P concentrations. The changes in N-to-P ratios were closely correlated with the changes in N and P concentrations, indicating that the changes in both N and P concentrations due to N addition can drive N and P stoichiometry, but the relative sizes of the contributions of N and P varied greatly with different nutrient limitations. Specifically, the changes in N-to-P ratios may indicate a minimum threshold, which is consistent with the homeostatic mechanism. In brief, increasing N deposition may aggravate P limitation under N-limited conditions but improve P limitation under P-limited conditions. The findings highlight the importance of nutrient-limited conditions in the stoichiometric response to N addition, thereby advancing our ability to predict global plant growth with increasing N deposition in the future.
为了检验养分限制条件可以决定氮（N）和磷（P）化学计量对 N 添加响应的假设，我们进行了一项荟萃分析，以确定在 N 限制、N 和 P 共同限制以及 P 限制下，叶片 N 和 P 浓度以及 N:P 比对 N 添加的不同响应。在 N 限制下，N 添加分别增加了叶片 N:P 比和 N 浓度 46.2%和 30.2%，在 N 和 P 共同限制下增加了 18.7%和 19.7%，在 P 限制下增加了 4.7%和 12.9%。然而，在不同养分限制下，叶片 P 浓度对 N 添加的响应不同，分别在 N 限制、P 限制和 N 和 P 共同限制下观察到负、正和中性影响。一般来说，N 添加对草本植物 N:P 比和 N 浓度的影响明显大于木本植物（除了 N 限制下的 N:P 比），但 P 浓度的情况则相反。N:P 比的变化与 N 和 P 浓度的变化密切相关，表明由于 N 添加导致的 N 和 P 浓度的变化可以驱动 N 和 P 化学计量，但不同养分限制下 N 和 P 的相对贡献大小差异很大。具体来说，N:P 比的变化可能表明存在一个最小阈值，这与体内平衡机制一致。简而言之，增加 N 沉降可能会加剧 N 限制条件下的 P 限制，但会改善 P 限制条件下的 P 限制。这些发现强调了养分限制条件在对 N 添加的化学计量响应中的重要性，从而提高了我们在未来随着 N 沉降增加预测全球植物生长的能力。
