Rain- and water-use efficiencies of a shrub ecosystem and its resilience to drought in the Central Asia region during 2000–2014

摘要

As one of the more dominant and relatively stable ecosystems in arid Central Asia, the shrub ecosystem plays an important role in the maintenance of ecosystem stability; therefore, interpreting the results and increased understanding of rain use efficiency (RUE), water use efficiency (WUE) and the corresponding resilience to drought may result in positive environmental implications for the conservations and restoration of vegetation in this arid region. In this study, the RUE and WUE of a shrub ecosystem in Central Asia were analyzed and ecosystem resilience based on RUE and WUE was evaluated by the contextual Mann-Kendall test and resilience index using datasets including MODIS and CRU data during 2000–2014. The results indicated that RUE and WUE had spatial patterns that decreased from low latitudes to high latitudes across the region. At the whole-region scale, RUE and WUE were relatively stable in most years. Spatially, more than half of the shrub patch area experienced an increasing trend in RUE and WUE over the past 15 years. For resilience assessments, a negative correlation was found between resistance and recovery, as reflected by WUE and RUE. The WUE- and RUE-based resilience components both captured a drop in WUE and RUE related to drought occurrence in shrubs, but the magnitudes of the RUE indices were much higher than those of the WUE indices in most shrub patches, suggesting that the negative impact of RUE on carbon accumulation of shrub encountering drought was greater than that of WUE. Based on RUE and WUE, resilience assessments were consistent in 41.81% of the shrub patch area and different over 58.19% of the area. Considering the characteristics of ET and precipitation datasets and convenient accessibility of precipitation data in underdeveloped areas, RUE should be easy to use in assessing ecosystem resilience to extreme drought.