Ecological mechanisms underlying aridity thresholds in arid mining areas for vegetation guided restoration

The identification of ecological threshold is one of the important technical links in the vegetation guided restoration in arid mining areas, and the aridity threshold is a very important one among many key ecological thresholds. There will be sudden changes in the structure and functional attributes of the vegetation system in mining areas in different aridity threshold areas. It is very important to clarify the underlying ecological mechanism under different aridity thresholds for the determination of the reasonable degree of intervention and the direction of guiding the restoration. The existing research lacks a systematic review of the ecological mechanism that causes these mutations. A conceptual model of abrupt response of dryland ecosystem to drought is constructed in this paper, which summarizes the response of dryland ecosystem to drought degree as vegetation recession stage, “soil imbalance” stage and system collapse stage. In the declining stage of vegetation, it is mainly manifested in the changes of photosynthetic physiological adaptation mode and characteristics of vegetation in response to extreme water shortage environment. The “soil imbalance” stage mainly involves the complex interaction between soil and plants, which is transmitted through soil erosion, shrub invasion and biogeochemical pathways. In the stage of system collapse, the plant-plant and plant-atmosphere interaction triggered by plant physiological limits leads to a sharp reduction in system diversity. In the future, in-depth research can be conducted on the selection of typical plants, the expansion of research scale, the development mechanism of drought induced shrub traits, the mutation mechanism of biogeochemical cycle induced by drought, the time node at which plants can resume their physiological activities after drought stress is relieved, and the mechanism of biological crust production. This study provides a basic framework for understanding the potential ecological mechanism of aridity threshold for vegetation guided restoration in arid mining areas, also provides an ecological basis for scientifically determining the reasonable degree of intervention and guiding the direction of restoration in the later stage.