Abstract: Some ecosystems could shift from one stable state into another alternative stable state as approaching fold-bifurcation point (or tipping point). In ecosystem level, however, previous studies in dryland ecosystems mainly focused on hydrologic processes, and largely ignored other processes, such as wind erosion. Furthermore, previous studies generally didn't take the interaction between external driver and ecosystem state into consideration when studying regime shifts. Using a mean-field model, this paper investigated the dynamics of regime shifts in drylands with drift potential as external driver. The results suggested that the vegetation state and the bare state were the only stable states when drift potential was smaller than 93 VU and 230 VU, respectively. And drift potential was between 93 VU and 230 VU, both vegetation state and bare state could stably exist. Moreover, considering the interaction between external driver and ecosystem state would greatly extend the region of stable equilibrium to higher drift potential, i.e., tipping points in degradation moved from 230 VU (93 VU) under non-interactive situation to 337 VU (213 VU) under strong interactive situation. This study suggests that one can the dynamics of dryland ecosystems with drift potential as driver and should consider the interaction between drift potential and system state. This work puts forward a novel idea and view for researches in dryland ecosystems, and provides theoretical supports for maintaining ecosystem functions and restoring degraded ecosystems in drylands.

Key words: regime shifts, desertification, drift potential, external driver, dryland, ecosystems