Environmental changes in stream ecosystems caused by human activities and climate change can have large-scale ecological implications due to their potential impact on key food web dynamics. Stream and riparian food webs are linked through the reciprocal flux of subsidy resources (i.e., emergent aquatic insects to riparian zone, and terrestrial invertebrate in-fall into streams) that allow aquatic and terrestrial consumers to exhibit stabilizing consumer-resource (C-R) interactions. Consumers couple multiple energy channels (i.e., exhibit “multi-channel omnivory") by feeding on alternate subsidy resources when in situ resources are scare. The asynchrony in timing of in situ resource and subsidy biomass allows consumers to have a constant supply of food resources, having a stabilizing effect on coupled stream-riparian food webs. The seasonal, asynchronous, flux of emergent aquatic insect and riparian invertebrate in-fall is governed by environmental conditions (e.g., insect phenology is largely temperature driven). Therefore, changes in local environmental conditions, such as those caused by climate change, can alter the timing of this flux, potentially leading to destabilizing C-R interactions. The consumer-resource-subsidy model developed by Huxel & McCann (1998), will be used to examine how changes in the timing (i.e., synchrony) of in situ resource and reciprocal subsidy abundance alter the stability of C-R interactions, and thus food web dynamics.
Results/Conclusions
We can investigate how environmental changes influence food web dynamics by manipulating the temporal asynchrony of resource and subsidy availability. For example, in situ aquatic resource abundance and terrestrial subsidy abundance may become more synchronous in time if climate change increases local temperatures and thereby advances emergence times. This can cause low in situ resource biomass to occur before peak terrestrial subsidies biomass, forcing aquatic consumers to go through a period of low overall resource availability, creating unstable C-R interactions and de-stabilizing food web dynamics. This research will help develop theoretical understanding of how alterations in the timing of reciprocal subsidy fluxes in stream and riparian food webs influence food web stability. Thus, we can make predictions as to how agricultural land-use changes that alter environmental conditions in riparian zones influence key stream and riparian interactions, and their potential downstream effects on food web stability and ecosystem function.