Changes in the relationship between climate variables and vegetation carbon uptake in East Asia

To understand the carbon cycle in East Asia in the context of rising CO₂, we analyzed a land carbon cycle dataset (TRENDY) from 1982 to 2020, examining the relationship between vegetation carbon uptake and two climate variables (i.e. precipitation and surface temperature) during the vegetation growing season (March to September). Our results show that, since the early 2000s, the relationship between gross primary production (GPP) and surface temperature has strengthened, while the relationship between GPP and precipitation has weakened in East Asia. Further analyses suggest that this strengthening of the GPP-surface temperature relationship is primarily due to a combination of CO₂ fertilization effects and significant increases in surface temperature, which lead to reduced soil moisture and increased water use efficiency in vegetation. This appears to result in an increase in GPP in the long term along with the absence of significant changes in precipitation. As a result, vegetation carbon uptake is less dependent on precipitation and more correlated with surface temperature in the recent decades. This result indicates that the relationship between vegetation carbon uptake and climate variables is non-stationary, and therefore requires careful attention to properly develop carbon mitigation plans through afforestation.