Recovery of ecosystem carbon and water fluxes after drought in China

Abstract

Drought recovery time is a crucial indicator of ecosystem resilience. However, existing drought recovery quantification methods have some limitations in terms of drought identification and selection of recovery factors. In addition, drought recovery time in China and related impacts on different landcover types are largely unknown. Therefore, the present study sought to develop a new drought recovery quantification system that considers recovery of ecosystem carbon- and water-related variables in China across seasons (wet and dry) and landcover types. The results showed that drought conditions worsened, especially in northern and western China, from 1982 to 2016. Drought had a strong effect on soil water storage (SWS), with runoff and SWS decreasing in more than 65% of the study area after drought. Drought led to decreases in gross primary productivity (GPP) and water use efficiency (WUE) over 58.7% and 45.2% of the total area, respectively. The mean drought recovery time of SWS (10.4 months) was much longer than that of GPP (3.2 months), WUE (3.7 months), and runoff (2.5 months), especially in northern China. Drought-reduced carbon and water needed more time to recover from drought in grasslands than in other landcover types due to the lower water availability and high evaporative demand. The mean recovery time after dry season drought was longer than that after wet season drought. In a comparison of recent (2001–2016) and past (1982–2000) periods, increased recovery times for runoff and SWS were observed for all landcover types except for SWS (-0.4 month) in grasslands. However, recent recovery times for GPP and WUE were shorter than that in the past. Highly decreased recovery times for GPP (-2.2 months) and WUE (-2.4 months) were found in grasslands. Runoff recovery time increased by 4.9 months in forest and SWS recovery time increased by 1.4 months in cropland. These results improved our understanding of regional drought recovery mechanisms and future trends in different landcover types.