Global variability in belowground autotrophic respiration in terrestrial ecosystems

Globally, mean RA was 43.8±0.4 Pg C yr-1, with a temporally increasing trend of 0.025±0.006 Pg C yr-2 from 1980 to 2012. Such an incremental trend was widespread, representing 58 % of global land. For each 1 ĝC increase in annual mean temperature, global RA increased by 0.85±0.13 Pg C yr-2, and it was 0.17±0.03 Pg C yr-2 for a 10 mm increase in annual mean precipitation, indicating positive feedback of RA to future climate change. Precipitation was the main dominant climatic driver controlling RA, accounting for 56 % of global land, and was the most widely spread globally, particularly in dry or semi-arid areas, followed by shortwave radiation (25 %) and temperature (19 %). Different temporal patterns for varying climate zones and biomes indicated uneven responses of RA to future climate change, challenging the perspective that the parameters of global carbon stimulation are independent of climate zones and biomes. The developed RA dataset, the missing carbon flux component that is not constrained and validated in terrestrial ecosystem models and Earth system models, will provide insights into understanding mechanisms underlying the spatial and temporal variability in belowground vegetation carbon dynamics. The developed RA dataset also has great potential to serve as a benchmark for future data-model comparisons. The developed RA dataset in a common NetCDF format is freely available at https://doi.org/10.6084/m9.figshare.7636193 (Tang et al., 2019).