The Impacts of Land Use on Cross-Ecosystem Resource Subsidies

Headwater streams are largely supported by terrestrial resource subsidies (e.g. leaf litter, terrestrial invertebrates), and also provide food sources (e.g. emergence insects) for many terrestrial consumers. These reciprocal subsidies are mainly controlled by the dense canopy which domains in this landscape. However, land use related habitat degradation and affected the fluxes of subsidies, which cause a decline in subsidy quantity and quality, and consequently influence food web dynamics and stability in recipient ecosystems. Despite the awareness that land use damps the strengths of reciprocal subsidies and thus weakens the linkage between aquatic and terrestrial ecosystems, empirical studies are limited in determining a possible threshold range for land use regarding to its ecological consequences on reciprocal subsidies, i.e. how many forest should be kept to maintain biodiversity and ensure ecosystem functions. This study will address (1) how reciprocal subsidies are influenced by land use in headwaters; (2) what are the ecological consequences of changed subsidies on aquatic and terrestrial ecosystems due to land use.