Masters Programme in Ecosystems and Environmental Change, Department of Life Sciences, Imperial College London, Ascot, UK.
Department of Environmental Systems Science, ETH, Zurich, Switzerland.
Commun Biol. 2021 Apr 12;4(1):462. doi: 10.1038/s42003-021-01985-7.
There is huge uncertainty about how global exchanges of carbon between the atmosphere and land will respond to continuing environmental change. A better representation of photosynthetic capacity is required for Earth System models to simulate carbon assimilation reliably. Here we use a global leaf-trait dataset to test whether photosynthetic capacity is quantitatively predictable from climate, based on optimality principles; and to explore how this prediction is modified by soil properties, including indices of nitrogen and phosphorus availability, measured in situ. The maximum rate of carboxylation standardized to 25 °C (V) was found to be proportional to growing-season irradiance, and to increase-as predicted-towards both colder and drier climates. Individual species' departures from predicted V covaried with area-based leaf nitrogen (N) but community-mean V was unrelated to N, which in turn was unrelated to the soil C:N ratio. In contrast, leaves with low area-based phosphorus (P) had low V (both between and within communities), and P increased with total soil P. These findings do not support the assumption, adopted in some ecosystem and Earth System models, that leaf-level photosynthetic capacity depends on soil N supply. They do, however, support a previously-noted relationship between photosynthesis and soil P supply.
大气与陆地之间的碳全球交换对持续环境变化的响应存在巨大的不确定性。为了使地球系统模型能够可靠地模拟碳同化，需要更好地代表光合作用能力。在这里，我们使用全球叶片性状数据集，根据最优性原理，检验光合作用能力是否可以从气候中定量预测；并探讨这种预测如何被土壤特性（包括原位测量的氮和磷可用性指数）所改变。发现标准化到 25°C 的羧化最大速率（V）与生长季节辐射成正比，并朝着更冷和更干燥的气候增加（如预测的那样）。个别物种的 V 偏离预测值与基于面积的叶片氮（N）有关，但 V 与社区平均值无关，而 N 又与土壤 C:N 比无关。相比之下，基于面积的磷（P）较低的叶片 V 较低（无论是在社区之间还是内部），而 P 随着总土壤 P 的增加而增加。这些发现不支持某些生态系统和地球系统模型所采用的假设，即叶片水平的光合作用能力取决于土壤 N 供应。然而，它们确实支持了先前注意到的光合作用与土壤 P 供应之间的关系。
