干旱区生态系统跃变:以输沙势为外部驱动力

Regime Shifts in Dryland Ecosystems:drift potential as external driver

生态系统靠近跃变点时可能发生跃变,骤然从一种稳定状态跃变到另外一种稳定态。然而以往关于干旱区的系统跃变的研究主要集中于水文过程,对其他过程(如风积过程)关注不够,并且很少考虑外部驱动力与系统状态之间的交互作用。我们以输沙势(风积过程)为系统跃变的外部驱动力,利用空间隐式模型,研究干旱区生态系统的跃变动态,并考虑输沙势与系统状态之间的交互作用对系统跃变动态的影响。结果表明:当输沙势较低(<93VU)或较高(>230VU)时植被态和裸地态分别是唯一的稳定态,而当输沙势为93~230VU时,植被态和裸地态都可稳定存在。考虑交互作用使系统退化(恢复)时的跃变点从无交互作用的230VU(93VU)推移到了高强度交互作用的337VU(213VU),在研究干旱区生态系统的系统跃变时,可以以输沙势为外部驱动力,并考虑输沙势与系统状态之间交互作用。

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 from230 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.