We use the Multiple Element Limitation (MEL) model to examine responses of 12 ecosystems to elevated carbon dioxide (CO₂), warming, and 20% decreases or increases in precipitation. Ecosystems respond synergistically to elevated CO₂, warming, and decreased precipitation combined because higher water-use efficiency with elevated CO₂ and higher fertility with warming compensate for responses to drought. Response to elevated CO₂, warming, and increased precipitation combined is additive. We analyze changes in ecosystem carbon (C) based on four nitrogen (N) and four phosphorus (P) attribution factors: (1) changes in total ecosystem N and P, (2) changes in N and P distribution between vegetation and soil, (3) changes in vegetation C:N and C:P ratios, and (4) changes in soil C:N and C:P ratios. In the combined CO₂ and climate change simulations, all ecosystems gain C. The contributions of these four attribution factors to changes in ecosystem C storage varies among ecosystems because of differences in the initial distributions of N and P between vegetation and soil and the openness of the ecosystem N and P cycles. The net transfer of N and P from soil to vegetation dominates the C response of forests. For tundra and grasslands, the C gain is also associated with increased soil C:N and C:P. In ecosystems with symbiotic N fixation, C gains resulted from N accumulation. Because of differences in N versus P cycle openness and the distribution of organic matter between vegetation and soil, changes in the N and P attribution factors do not always parallel one another. Differences among ecosystems in C-nutrient interactions and the amount of woody biomass interact to shape ecosystem C sequestration under simulated global change. We suggest that future studies quantify the openness of the N and P cycles and changes in the distribution of C, N, and P among ecosystem components, which currently limit understanding of nutrient effects on C sequestration and responses to elevated CO₂ and climate change.

中文翻译：

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N 和 P 限制气候变化下生态系统中的 C：养分再分配、积累和化学计量的作用

我们使用多元素限制 (MEL) 模型来检查 12 个生态系统对二氧化碳 (CO ₂ ) 升高、变暖和降水减少或增加 20% 的响应。生态系统对 CO _{2升高、变暖和降水减少的组合做出协同响应，因为 CO 2}升高导致的用水效率提高以及变暖导致的肥力提高补偿了对干旱的反应。对升高的 CO _2的反应，变暖和降水增加相结合是累加的。我们根据四种氮 (N) 和四种磷 (P) 归因因子分析生态系统碳 (C) 的变化：(1) 生态系统总 N 和 P 的变化，(2) 植被和土壤之间 N 和 P 分布的变化， (3) 植被 C:N 和 C:P 比率的变化，以及 (4) 土壤 C:N 和 C:P 比率的变化。在合并的 CO ₂和气候变化模拟，所有生态系统都获得 C。这四个归因因子对生态系统 C 储存变化的贡献因生态系统而异，因为 N 和 P 在植被和土壤之间的初始分布不同以及生态系统 N 和 P 的开放性周期。N 和 P 从土壤到植被的净转移主导着森林的 C 响应。对于苔原和草地，C 增加也与土壤 C:N 和 C:P 增加有关。在具有共生固氮的生态系统中，碳的增加是由氮积累引起的。由于 N 与 P 循环开放度的差异以及植被和土壤之间有机质的分布，N 和 P 归因因子的变化并不总是相互平行。在模拟的全球变化下，生态系统之间碳营养相互作用的差异和木质生物量的相互作用会影响生态系统的碳固存。我们建议未来的研究量化 N 和 P 循环的开放性以及生态系统成分中 C、N 和 P 分布的变化，这目前限制了对养分对碳固存的影响和对 CO2 升高的响应的理解₂、气候变化。