Both internal feedbacks and preexisting heterogeneity of a physical template can produce biological patchiness in ecosystems. The relative importance of the two drivers might change over time, in response to changes in the external environment. This is especially relevant for ecosystems experiencing high environmental variability. We investigated the interaction between these two drivers—internal feedbacks and template heterogeneity (represented by variation in water permanence in this study)—using 9-year data on macrophyte (wetland) patch distribution collected from Sycamore Creek, a desert stream in Arizona, USA. Sycamore Creek is highly variable both in space and in time due to its flashy hydrograph. We used a lattice simulation model that considered both the spatial heterogeneity of the geomorphic template and the influence of local positive feedbacks on plant growth. We showed that the relative strengths of local feedbacks and the template effect varied with the hydrological condition in a given year. Overall, the effect of template heterogeneity increased in wetter and more frequently flooded years and the effect of internal positive feedback decreased. Averaging over the 9-year study period, the effect of local feedbacks on wetland distribution and abundance in Sycamore Creek was about twice that of template heterogeneity. In the driest years, it reached up to ~ 12 times. Our study suggested that compared to catastrophic floods, severe droughts—the type of hydrological change projected to become more frequent for the region under a changing climate—have a stronger legacy effect on the biotic community in subsequent years.

内部反馈和物理模板先前存在的异质性都会在生态系统中产生生物斑块。响应外部环境的变化，这两个驱动因素的相对重要性可能会随时间变化。这对于经历高度环境变化的生态系统尤其重要。我们使用从美国亚利桑那州的沙漠溪流Sycamore Creek收集的9年大型植物（湿地）斑块分布数据，研究了这两个驱动因素之间的相互作用（内部反馈和模板异质性（在本研究中以水的持久性表示）。 。Sycamore Creek的水文浮华，因此在空间和时间上都有很大的变化。我们使用了一个晶格模拟模型，该模型考虑了地貌模板的空间异质性以及局部正反馈对植物生长的影响。我们表明，在特定年份，当地反馈的相对强度和模板效应随水文条件而变化。总体而言，在更湿和更频繁的淹水年份中，模板异质性的影响增加，而内部正反馈的影响则减小。在为期9年的研究期内，当地平均反馈对美国梧桐溪湿地分布和丰度的影响约为模板异质性的两倍。在最干旱的年份，它达到了约12倍。我们的研究表明，与灾难性洪水相比，