Xu Zhiwei, Mason Joseph A, Xu Chi, Yi Shuangwen, Bathiany Sebastian, Yizhaq Hezi, Zhou Yali, Cheng Jun, Holmgren Milena, Lu Huayu
School of Geography and Ocean Science, Nanjing University, Nanjing 210023, China.
Department of Geography, University of Wisconsin-Madison, WI 53706, USA.
Sci Adv. 2020 Feb 26;6(9):eaay8020. doi: 10.1126/sciadv.aay8020. eCollection 2020 Feb.
Dune systems can have alternative stable states that coexist under certain environmental conditions: a vegetated, stabilized state and a bare active state. This behavior implies the possibility of abrupt transitions from one state to another in response to gradual environmental change. Here, we synthesize stratigraphic records covering 12,000 years of dynamics of this system at 144 localities across three dune fields in northern China. We find side-by-side coexistence of active and stabilized states, and occasional sharp shifts in time between those contrasting states. Those shifts occur asynchronously despite the fact that the entire landscape has been subject to the same gradual changes in monsoon rainfall and other conditions. At larger scale, the spatial heterogeneity in dune dynamics averages out to produce relatively smooth change. However, our results do show different paths of recovery and collapse of vegetation at system-wide scales, implying that hysteretic behavior occurs in spatially extended systems.
一种植被覆盖、稳定的状态和一种裸露活跃的状态。这种行为意味着随着环境逐渐变化，可能会从一种状态突然转变为另一种状态。在这里，我们综合了中国北方三个沙丘场144个地点的地层记录，这些记录涵盖了该系统12000年的动态变化。我们发现活跃状态和稳定状态并存，并且在这些截然不同的状态之间偶尔会出现时间上的急剧转变。尽管整个地貌都受到季风降雨和其他条件相同的逐渐变化影响，但这些转变是异步发生的。在更大尺度上，沙丘动态的空间异质性平均化，产生相对平滑的变化。然而，我们的结果确实显示了全系统尺度上植被恢复和崩溃的不同路径，这意味着在空间扩展系统中会出现滞后行为。
