The future ecosystem carbon cycle has important implications for biosphere-climate feedback. The magnitude of future plant growth and carbon accumulation depends on plant strategies for nutrient uptake under the stresses of nitrogen (N) versus phosphorus (P) limitations. Two archetypal theories have been widely acknowledged in the literature to represent N and P limitations on ecosystem processes: Liebig's Law of the Minimum (LLM) and the Multiple Element Limitation (MEL) approach. LLM states that the more limiting nutrient controls plant growth, and commonly leads to predictions of dramatically dampened ecosystem carbon accumulation over the 21st century. Conversely, the MEL approach recognizes that plants possess multiple pathways to coordinate N and P availability and invest resources to alleviate N or P limitation. We implemented these two contrasting approaches in the E3SM model, and compiled 98 in situ forest N or P fertilization experiments to evaluate how terrestrial ecosystems will respond to N and P limitations. We find that MEL better captured the observed plant responses to nutrient perturbations globally, compared with LLM. Furthermore, LLM and MEL diverged dramatically in responses to elevated CO₂ concentrations, leading to a two-fold difference in CO₂ fertilization effects on Net Primary Productivity by the end of the 21st century. The larger CO₂ fertilization effects indicated by MEL mainly resulted from plant mediation on N and P resource supplies through N₂ fixation and phosphatase activities. This analysis provides quantitative evidence of how different N and P limitation strategies can diversely affect future carbon and nutrient dynamics.

中文翻译：

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在氮和磷限制的竞争假设下植物对二氧化碳升高的反应

未来生态系统碳循环对生物圈-气候反馈具有重要影响。未来植物生长和碳积累的程度取决于植物在氮 (N) 与磷 (P) 限制胁迫下吸收养分的策略。两种代表生态系统过程中 N 和 P 限制的原型理论在文献中得到了广泛认可：李比希最小值定律 (LLM) 和多元素限制 (MEL) 方法。法学硕士指出，限制性更强的养分控制着植物生长，通常会导致 21 世纪生态系统碳积累急剧减少的预测。相反，MEL 方法认识到植物拥有多种途径来协调 N 和 P 的可用性并投入资源来缓解 N 或 P 的限制。我们在 E3SM 模型中实施了这两种对比方法，并编制了 98 个原位森林氮或磷施肥实验，以评估陆地生态系统如何应对氮和磷的限制。我们发现，与 LLM 相比，MEL 更好地捕捉了观察到的植物对全球营养扰动的反应。此外，LLM 和 MEL 对 CO ₂浓度升高的反应存在显着差异，导致到21 世纪末CO ₂施肥对净初级生产力的影响出现两倍的差异。 MEL表明较大的CO _{2施肥效应主要是植物通过N 2}固定和磷酸酶活性调节N和P资源供应所致。该分析提供了不同的氮和磷限制策略如何对未来碳和养分动态产生不同影响的定量证据。