Restored vegetation is more resistant to extreme drought events than natural vegetation in Southwest China

Abstract

Large scale Ecosystem restoration projects (ERPs) have been implemented to restore vegetation and increase carbon stocks across China. However, whether restored vegetation is strongly resistant to Extreme drought events (EDEs) remains unclear, especially when compared to natural vegetation. Therefore, we used the standardized anomaly of 3-month Standard Precipitation-Evapotranspiration Index (SPEI) to characterize the spatial-temporal trends of EDEs, and figured out the capacity of restored vegetation to withstand the strongest EDE in Southwest China by analyzing their changes of Gross Primary Productivity (GPP) and Water Use Efficiency (WUE). The results showed that Southwest China had experienced six typical EDEs with increasing frequency and severity from 1982 to 2017, particularly the EDE during 2009-2010 (EDE 2009/2010) which had the longest duration and strongest severity. Overall, the EDE 2009/2010 substantially suppressed the vegetation GPP and ecosystem WUE in both restored and natural vegetation area. Compared with natural vegetation, the GPP and WUE of restored vegetation was relative higher and moreover, their GPP decreased more slowly during the EDE 2009/2010 and increased more quickly during the recovery period. This indicates that restored vegetation had a higher drought resistance to the EDE than natural vegetation. Additionally, karst landforms have a stronger negative impact on vegetation GPP and WUE during the EDE. Furthermore, the reduction in the afforestation areas was more obviously observed than that in natural forest areas. Therefore, we suggest that vegetation suitable for regional characteristics should be selected during vegetation restoration, such as afforestation in the non-karst areas.

Keywords: Afforestation; GPP; Grass planting; Karst; WUE.