The increasing rate of net carbon uptake in Eurasia has been declining since the early 2000s.

Abstract

The analysis of terrestrial ecosystem carbon dynamics, based on scarce carbon flux observations or carbon flux products simulated by reanalysis meteorological data, has great uncertainties. A more accurate understanding of carbon dynamics in Eurasia was achieved by using a carbon flux dataset (CFD) from meteorological stations with quasi-observational characteristics. The growth of net carbon uptake of ecosystems over Eurasia has been decreasing since the early 2000s. The net ecosystem productivity (NEP) increased significantly with the growth rate of 8.7 × 10^-3 g C m^-2d^-1 yr^-1 in spring, summer, and autumn (SSA) during 2003-2011 (p < 0.05), which was correlated with the enhanced vegetation index (EVI) and land surface water index (LSWI). This growth was mostly in dry subhumid and humid regions. However, the change in Eurasian NEP was not significant after 2011. Additionally, about 79 % of the stations in Eurasia were in net carbon uptake in SSA, and net carbon emission stations were mainly located in southwestern Eurasia. The intensity of net carbon uptake was highest in the forest, with a mean carbon uptake of 1.73 ± 0.76 g C m^-2d^-1 in SSA during 2003-2018, and almost all stations demonstrated carbon uptake. During 2011-2018, the number of stations experiencing reduced NEP exceeded those with increased NEP, and this ratio was higher compared to 2003-2011, mainly due to the decrease in EVI and LSWI. The rate of NEP decline at stations with reduced NEP was 5.2 × 10^-3 g C m^-2d^-1 yr^-1 faster during 2011-2018 than in the previous period (p < 0.01). Most of the decreases in NEP during 2011-2018 occurred in cropland, grassland and urban land. The spatio-temporal dynamic analysis of Eurasian NEP could provide references for effective carbon management.