A proposed approach to quantify drought recovery time and its influencing factors in Yangtze River Basin of China

Recovery time of an ecosystem from drought is an important indicator of assessing drought impacts and ecosystem resilience. The lagged effect reflects the drought resistance capacity of ecosystems and serves as the initial characteristic of drought recovery. However, among the previous studies that concentrated on quantifying drought recovery time, none have considered the influence of lagged effect during the process of quantifying recovery time. This study introduces a novel approach for quantify drought recovery time by accounting for the lagged effect of drought on ecosystems. The factors affecting recovery time are analyzed using random forest regression model. The dominant factors and their respective patterns of influence on recovery time are identified through assessments of variable importance and response functions, respectively. The results show that the average recovery time in the Yangtze River Basin is approximately 7.8 months, with the longest recovery time occurs in the western and southeast regions, and the shortest recovery time in the central and northeastern regions. Ecosystems in some areas of the central and northeast regions were fully recovered before the end of drought. For the influencing factors of recovery time, the most important one is precipitation during drought recovery period (PDDR), but its impact spatially varies. Higher PDDR shortens the recovery time in the western part of the basin, while a lower PDDR lengthens the recovery time in the central, northeastern and southeastern parts. Taking the lagged effect of drought on ecosystems into account in the quantification of drought recovery time can alleviate the discrepancies in the spatial distribution of recovery time assessed with diverse drought recovery criteria. The proposed approach can be used to compromise the contradictory conclusions that have emerged in previous studies related to drought recovery. This study presents a novel methodology for quantifying drought recovery time, which contributes to a more comprehensive understanding of the drought recovery process.