Preferred Drought Index Extraction and Dynamic Drought-Induced Effects on Terrestrial Ecosystem Exploration in China since 2000

Abstract

Drought has threatened sustainability in terrestrial ecosystems. Although a series of indices have been proposed, they have largely overlooked the performance in characterizing regional or local drought, which is significant in acknowledging the impacts of drought on regional carbon cycling. To extract site-specific optimal drought index for vegetation in China, vegetation net primary production (NPP) estimated by Terrestrial Ecosystem Carbon Flux model, was compared with 11 worldwide-used indices, through sensitivity analysis and Generalizes Estimation Equation method. It was found that NPP in northern areas were significantly sensitive and correlated to 7 ~ 11 drought indices, whereas southern areas were sensitive to 1 ~ 4 indices. Among the drought indices, moisture index was highlighted as the best one, followed by standardized precipitation index, effective drought index, drought reconnaissance index, and standardized precipitation evapotranspiration index. Using optimal drought indices for local applications, the dynamics of drought and its impact on vegetation were quantified from 2000 to 2022. A general increase in vegetation NPP and decrease in drought were demonstrated in major northern and eastern areas. Moderately-extremely drought led to > 20% and even > 40% loss in NPP across northern and northwestern areas, much larger than the loss in southern areas. Moreover, forests were exposed to a mean loss of −20.1% and standard deviation of 13.2% in NPP, smaller than croplands and grasslands. These results contribute to a better understanding of drought dynamic and coupling of vegetation production, and guide for planning mitigations in drought-prone hotpots to ensure region's resilience.

Keywords: drought index, net primary production, forests, croplands, grasslands