Multivariate drives and their interactive effects on the ratio of transpiration to evapotranspiration over Central Asia ecosystems

Abstract

The ratio of vegetation transpiration to evapotranspiration (T/ET) characterizes the role of vegetation in surface-atmosphere interactions, affecting ecosystem productivity and the global carbon and water balances. Therefore, isolating and identifying the spatiotemporal characteristics of T/ET and its response to the individual and interactive effects of climatic factors will help us better understand the carbon and water cycle characteristics of ecosystems. The arid region of Central Asia has always been in the restricted area of ​​carbon-water cycle observations due to scarce station observations, harsh climatic conditions, and severe anthropogenic disturbances. Using a specific Arid Ecosystem Model (AEM), this study explored the temporal and spatial dynamic patterns of T/ET of different plant functional types (PFTs) in drylands of Central Asia based on multi-climate scenarios, and separated and quantified the independent and interactive effects of different environmental factors. The result indicated that precipitation dominated the areas of 86% (ET, evapotranspiration), 77% (T, transpiration), and 71% (the ratio of T/ET) in the arid region of Central Asia, respectively. The effect of temperature on the ratio of T/ET was negative and slight. And the temperature increase effect is only 9.7% of the negative effect of precipitation. Affected by the insignificant effect of CO2 enrichment on T, the interactive effect between climate change and CO2 effect appear to be little and negative. According to the vegetation growth and the spatial distribution of precipitation, we found that the southern Xinjiang region and the Turgay Plateau in northwestern Kazakhstan are the ecologically vulnerable areas in Central Asian. The results also indicated that general warming in this region may not have a direct and significant impact on vegetation T/ET in the future. We may need to pay more attention to the indirect effect of enhanced evaporation and reduced moisture on T/ET caused by future warming.