Contribution of drought-avoidant strategy to gross primary productivity of three forest ecosystems in China

As drought events become more frequent and intense around the world, ecosystem gross primary productivity (GPP) is greatly associated with the responses of plants to drought stress. Drought avoidance is a critical strategy for plants to maintain internal water status under water deficit. However, the relative importance of this strategy to GPP has yet to be investigated. In this study, we first developed a theoretical framework to quantify the relative contribution of drought-avoidant strategy to GPP (Imp) based on the relationship between predawn and midday vegetation optical depth (VOD) and the relationship between midday VOD and GPP, and then applied this framework to three forest ecosystems in China. The results showed that the Imp was much smaller in a subtropical evergreen broadleaf forest (CN-Din, 2.3 f 0.1 % and 6.6 f 0.1 % for the original and the resolution mismatch corrected Imp, respectively) and a subtropical evergreen needleleaf forest (CN-Qia, 23.6 f 0.8 % and 3.1 f 0.1 %, respectively) than in a typical temperate mixed forest (CN-Cha, 58.2 f 3.7 % and 66.4 f 0.7 %, respectively). This difference may primarily come from the differential water conditions among the three forests, as the available water was much higher and the drought intensity was much weaker in CN-Din and CN-Qia than in CN-Cha. This work, for the first time, quantified the relative importance of drought-avoidant strategy to GPP, which might be critical to ecosystem functioning under climate change, especially for ecosystems that had not developed effective drought-tolerant strategies in the past geological times.