A new radiation index predicts the gross primary production of diverse terrestrial ecosystems

Solar radiation is the primary energy source that drives the physical and biochemical processes and determines the gross primary production (GPP) of an ecosystem. Even though the relationship between solar radiation and GPP is acknowledged, no radiation index (RI) has been developed to estimate GPP. Using data consisting of a total of 267 site-years obtained from 54 flux sites of diverse ecosystems, we introduced a RI that showed a strong linear relationship with GPP. Importantly, the estimation of GPP using the RI is independent of ecosystem types, making it a simple and universal method to estimate the productivity of any terrestrial ecosystems. The results from this study demonstrated the reliable performance of the RI in estimating GPP and its potential application in upscaling and prediction.