Karssenberg Derek, Bierkens Marc F P, Rietkerk Max
Am Nat. 2017 Dec;190(6):E145-E155. doi: 10.1086/694413. Epub 2017 Oct 4.
Under gradual change of a driver, complex systems may switch between contrasting stable states. For many ecosystems it is unknown how rapidly such a critical transition unfolds. Here we explore the rate of change during the degradation of a semiarid ecosystem with a model coupling the vegetation and geomorphological system. Two stable states-vegetated and bare-are identified, and it is shown that the change between these states is a critical transition. Surprisingly, the critical transition between the vegetated and bare state can unfold either rapidly over a few years or gradually over decennia up to millennia, depending on parameter values. An important condition for the phenomenon is the linkage between slow and fast ecosystems components. Our results show that, next to climate change and disturbance rates, the geological and geomorphological setting of a semiarid ecosystem is crucial in predicting its fate.
在驱动因素逐渐变化的情况下，复杂系统可能会在截然不同的稳定状态之间切换。对于许多生态系统而言，这种关键转变的展开速度尚不清楚。在此，我们通过一个耦合植被与地貌系统的模型，探究半干旱生态系统退化过程中的变化速率。我们识别出了两种稳定状态——植被覆盖状态和裸地状态，并表明这两种状态之间的变化是一种关键转变。令人惊讶的是，植被覆盖状态和裸地状态之间的关键转变可能在几年内迅速发生，也可能在数十年至数千年的时间里逐渐发生，这取决于参数值。该现象的一个重要条件是生态系统中快慢不同的组成部分之间的联系。我们的结果表明，除了气候变化和干扰速率之外，半干旱生态系统的地质和地貌背景对于预测其命运至关重要。
