Soil nutrient availability regulated global carbon use efficiency

The carbon use efficiency (CUE) is a core ecosystem parameter that determines the proportion of gross primary productivity (GPP) kept by an ecosystem after self-consumption. Its patterns along climates have been investigated to some extents. However, large uncertainty still exists, especially regarding its relationships with soil nutrients. The objective of this study was to evaluate the CUE variations along soil nutrient gradients by utilizing multi-sources of data for the global terrestrial ecosystem. The global terrestrial ecosystem CUE was calculated based on remote sensing modeled ecosystem productivity data, as well as in-situ observation data. The pattern analysis showed that global croplands and grasslands are distributed in nutrient-richer regions than forests. Along waning nutrients, GPP and net primary productivity (NPP) exhibit an overall increasing trend, while CUE declines. Within each biome, GPP and NPP decrease along enhanced nutrients for forests and grasslands, while CUE exhibits an opposite pattern. Based on worldwide collected field plot data, CUE also decreases along a weakened nutrient gradient. The strengthened ecosystem CUE pattern along enhanced nutrients as resulted from both model and field measurements data underscores the foremost significances of nutrients for ecosystem efficiency, also entails more comprehensive incorporations of nutrients in the future modeling studies.