State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, College of Forestry, Northwest A & F University, Yangling, 712100, Shaanxi, China.
Department of Biological Sciences, Macquarie University, North Ryde, NSW 2109, Australia.
Nat Plants. 2017 Sep;3(9):734-741. doi: 10.1038/s41477-017-0006-8. Epub 2017 Sep 4.
Gross primary production (GPP)-the uptake of carbon dioxide (CO) by leaves, and its conversion to sugars by photosynthesis-is the basis for life on land. Earth System Models (ESMs) incorporating the interactions of land ecosystems and climate are used to predict the future of the terrestrial sink for anthropogenic CO . ESMs require accurate representation of GPP. However, current ESMs disagree on how GPP responds to environmental variations , suggesting a need for a more robust theoretical framework for modelling . Here, we focus on a key quantity for GPP, the ratio of leaf internal to external CO (χ). χ is tightly regulated and depends on environmental conditions, but is represented empirically and incompletely in today's models. We show that a simple evolutionary optimality hypothesis predicts specific quantitative dependencies of χ on temperature, vapour pressure deficit and elevation; and that these same dependencies emerge from an independent analysis of empirical χ values, derived from a worldwide dataset of >3,500 leaf stable carbon isotope measurements. A single global equation embodying these relationships then unifies the empirical light-use efficiency model with the standard model of C photosynthesis , and successfully predicts GPP measured at eddy-covariance flux sites. This success is notable given the equation's simplicity and broad applicability across biomes and plant functional types. It provides a theoretical underpinning for the analysis of plant functional coordination across species and emergent properties of ecosystems, and a potential basis for the reformulation of the controls of GPP in next-generation ESMs.
总初级生产力（GPP）——即叶片吸收二氧化碳（CO）并通过光合作用将其转化为糖——是陆地生命的基础。包含陆地生态系统与气候相互作用的地球系统模型（ESM）被用于预测人为 CO 陆地汇的未来。ESM 需要准确表示 GPP。然而，当前的 ESM 对 GPP 如何响应环境变化存在分歧，这表明需要一个更稳健的理论框架来进行建模。在这里，我们关注 GPP 的一个关键数量，即叶片内部与外部 CO 的比率（χ）。χ受到严格调节，取决于环境条件，但在当今的模型中仅以经验方式表示且不完整。我们表明，一个简单的进化最优性假设可以预测 χ 对温度、蒸气压亏缺和海拔的具体定量依赖性；并且这些相同的依赖性也可以从对来自全球超过 3500 个叶片稳定碳同位素测量的 χ 值的实证分析中得出。一个包含这些关系的单一全球方程，然后统一了经验光利用效率模型与 C 光合作用的标准模型，并成功预测了涡度协方差通量站点测量的 GPP。鉴于该方程的简单性和在生物群落和植物功能类型中的广泛适用性，这一成功引人注目。它为分析跨物种的植物功能协调性以及生态系统的新兴属性提供了理论基础，并为新一代 ESM 中 GPP 控制的重新制定提供了潜在基础。
