Am Nat. 2019 Mar;193(3):472-480. doi: 10.1086/701669. Epub 2019 Jan 18.
Ecosystems' responses to changing environmental conditions can be modulated by spatial self-organization. A prominent example of this can be found in drylands, where formation of vegetation patterns attenuates the magnitude of degradation events in response to decreasing rainfall. In model studies, the pattern wavelength responds to changing conditions, which is reflected by a rather gradual decline in biomass in response to decreasing rainfall. Although these models are spatially explicit, they have adopted a mean-field approach to grazing. By taking into account spatial variability when modeling grazing, we find that (over)grazing can lead to a dramatic shift in biomass, so that degradation occurs at rainfall rates that would otherwise still maintain a relatively productive ecosystem. Moreover, grazing increases the resilience of degraded ecosystem states. Consequently, restoration of degraded ecosystems could benefit from the introduction of temporary small-scale exclosures to escape from the basin of attraction of degraded states.
生态系统对环境变化的响应可以通过空间自组织来调节。在干旱地区，这种情况尤为明显，那里植被模式的形成减弱了降雨减少对退化事件的影响。在模型研究中，模式波长会对变化的条件做出响应，这反映在降雨减少时，生物量会逐渐下降。尽管这些模型是空间显式的，但它们在放牧方面采用了平均场方法。通过在建模放牧时考虑空间变异性，我们发现过度放牧可能导致生物量的急剧变化，从而导致在原本仍能维持相对生产力的生态系统的降雨率下发生退化。此外，放牧增加了退化生态系统状态的弹性。因此，引入临时小规模的围栏来逃避退化状态的吸引盆地，可能会使退化生态系统的恢复受益。
