Diverse photosynthetic capacity of global ecosystems mapped by satellite chlorophyll fluorescence measurements.

Photosynthetic capacity is often quantified by the Rubisco-limited photosynthetic capacity (i.e. maximum carboxylation rate, V). It is a key plant functional trait that is widely used in Earth System Models for simulation of the global carbon and water cycles. Measuring V is time-consuming and laborious; therefore, the spatiotemporal distribution of V is still poorly understood due to limited measurements of V. In this study, we used a data assimilation approach to map the spatial variation of V for global terrestrial ecosystems from a 11-year-long satellite-observed solar-induced chlorophyll fluorescence (SIF) record. In this SIF-derived V map, the mean V value for each plant function type (PFT) is found to be comparable to a widely used N-derived V dataset by Kattge et al. (2009). The gradient of V along PFTs is clearly revealed even without land cover information as an input. Large seasonal and spatial variations of V are found within each PFT, especially for diverse crop rotation systems. The distribution of major crop belts, characterized with high V values, is highlighted in this V map. Legume plants are characterized with high V values. This V map also clearly illustrates the emerging soybean revolution in South America where V is the highest among the world. The gradient of V in Amazon is found to follow the transition of soil types with different soil N and P contents. This study suggests that satellite-observed SIF is powerful in deriving the important plant functional trait, i.e. V, for global climate change studies.