Divergence and legacy in pantropical biomes net carbon uptake recovery from the El Niño

Occurring in 2015/2016, the strong El Niño has been shown to significantly reduce the pantropical net carbon uptake(1), and the pantropical aboveground biomass did not fully recover from the El Niño impacts till now(2). Both satellite observations and Earth system models demonstrated large but divergent responses in the pantropical carbon cycle during the 2015/16 El Niño(3, 4). However, the regional and biome-specific net carbon uptake in response to this El Niño event remain unclear. We hereby assimilated multiple sources of observations into an ecosystem model to constrain the terrestrial carbon cycle and analyzed the pantropical carbon cycle after the 2015/16 El Niño until 2020, and unveiled the recovery of biome-specific net carbon uptake over the pantropics. We estimated the pantropical net carbon emissions of 0.91 Pg C/yr during the peak El Niño year 2015 and the mean recovery fraction of biome-scale net carbon uptake was 0.77±0.07 during the recovery period 2016-2020 relative to the 2010-2014 period. Specifically, by de-coupling of soil and atmospheric moisture, we found that the vapor pressure deficit and soil moisture contribute counter-intuitively to the recovery of net carbon uptake in the tropical forests with lower soil moisture and higher atmospheric dryness intriguing net carbon uptake, whilst the soil moisture positively dominates in the recovery of net carbon uptake in the non-forest biomes. Additionally, the asynchronous recovery of gross primary productivity and ecosystem respiration slows down the recovery of regional net carbon uptake in the pantropics. These results suggest the dominance of water availability in the pantropical carbon cycle.