Food-web structures link multi-scale processes in complex landscapes

Complex landscapes are challenging to study because both the higher level contextual and interacting lower level mechanistic processes underpinning their ecological characteristics occur simultaneously. However, food-web structures can provide process insight in such landscapes by identifying these processes in specific contexts. Here, we used stable isotopes to identify spatially separate resources and infer resource flows underpinning food-web structures in a braided river. We found that river resources used by mobile consumers, including birds and fish, were spatially heterogeneous. Consumer resource use was related to four key structural food-web attributes: (1) spatiotemporal variation in foraging, (2) subsidies, (3) omnivory, and (4) ontogenetic niche shifts. Thus, both physical heterogeneity (contextual physical processes) and adaptive characteristics of consumers (mechanistic processes) were likely contributing to important food-web structures. Identifying these food-web structures in landscapes, across scales of resource use and spatial distribution, provides a way to identify processes and scales likely contributing to food-web stabilization.