Regional Responses of Vegetation Productivity to the Two Phases of ENSO

The two phases of El-Nino-Southern Oscillation (ENSO) influence both regional and global terrestrial vegetation productivity on inter-annual scales. However, the major drivers for the regional vegetation productivity and their controlling strengths during different phases of ENSO remain unclear. We herein disentangled the impacts of two phases of ENSO on regional carbon cycle using multiple data sets. We found that soil moisture predominantly accounts for similar to 40% of the variability in regional vegetation productivity during ENSO events. Our results showed that the satellite-derived vegetation productivity proxies, gross primary productivity from data-driven models (FLUXCOM) and observation-constrained ecosystem model (Carbon Cycle Data Assimilation System) generally agree in depicting the contribution of soil moisture and air temperature in modulating regional vegetation productivity. However, the ensemble of weakly constrained ecosystem models exhibits non-negligible discrepancies in the roles of vapor pressure deficit and radiation over extra-tropics. This study highlights the significance of water in regulating regional vegetation productivity during ENSO. ENSO, a significant climate phenomenon, profoundly influences ecosystem productivity from regional to global scales. Yet, accurately pinpointing the attributions of different climate factors that control Gross Primary Productivity (GPP) during ENSO events remains challenging, partly due to large uncertainties in existing GPP data. Through extensive analysis using various data sets, we found that soil moisture plays a dominant role in controlling GPP across most continents. This implies that current terrestrial biosphere models might underestimate the importance of soil moisture in driving productivity during ENSO events. Addressing this gap in understanding is crucial for refining and properly constraining the related processes in terrestrial biosphere models. Soil moisture predominantly governs vegetation productivity changes during El-Nino-Southern Oscillation (ENSO) events Satellite-derived vegetation indices consistently support the predominant influence of water on vegetation productivity ENSO triggers varying effects on vegetation productivity across different regions, with distinct impacts during El Nino and La Nina