New physiological thresholds improve soil desiccation prediction rationality in apple orchards converted from farmland on the Chinese Loess Plateau

Abstract

AbstractThe dry soil layer (DSL), as a typical indicator for degradation in soil water supply capacity and soil drought, could provide important information for land use and reconstruction in semiarid and arid areas. However, the traditional index of DSL assessment neglected the water absorption characteristics and drought resistance of different crops and lacked uniformity and comparability. These may misjudge the occurrence and severity of the DSL and bring uncertainty to land development and vegetation selection. In this study, the DSL severity of the main production zone of apples in the Chinese Loess Plateau was reassessed using new plant physiological indices covering the next 60 years (2020–2080) under four general circulation models. Physiological indices were established based on the response of leaf net photosynthetic (TPN) and transpiration rate (TTR) to soil available water which is the difference between soil moisture and permanent wilting point (n = 113). The environment policy integrated climate (EPIC) model was used to predict future soil water dynamics and drought yield loss (YL). The results showed that TPN and TTR significantly slowed down the accumulation of DSL severity quantitative index (QI, based on thickness moisture and formation depth of DSL) and enhanced the correlation between DSL and YL, which correlation coefficient increased from 0.51 to 0.73 and 0.64. Forming serious DSL (QI >0.5) has slowed from 2040 to 2055 years. Moreover, future climate change accumulatively reduced 9.95%–14.18% of the YL. These results indicated that the traditional method overestimated the environmental contradiction between economic benefits and eco‐hydrology of apple orchards, which could send unreliable messages to policymakers to restrict further development of apple industries. This study emphasized that evaluating DSL based on plant physiological threshold reflected better soil desiccation level and YL, which will contribute to further study of the sustainable development of fragile ecosystems.