Stream ecosystem responses to spatially variable landcover: A model with implications for riparian restoration

D.D. Hart, T.E. Johnson, J.N. McNair, and P. Srivastava. Patrick Center for Environmental Research, Academy of Natural Sciences, 1900 Benjamin Franklin Parkway, Philadelphia PA 19103

The protection and restoration of riparian habitats has become a central focus of programs to improve degraded streams. Little is known, however, about how the structural attributes of riparian corridors such as the width and continuity of natural vegetation along entire stream networks affect stream ecosystems. It is therefore likely that we are not implementing riparian restoration in an optimal way, especially to improve instream ecological conditions. We present a generalized, conceptual framework that establishes a relationship between the “stress” imposed on streams due to different spatial patterns of landuse/landcover within watersheds, and the response of biologically-determined ecosystem characteristics to stress. We then develop a simple mathematical model based on this framework, and use it to illustrate basic principles about how stream ecosystems respond to the pattern of landuse/landcover along their length and to riparian restoration at particular stream locations. The model provides new perspectives and quantitative tools for examining how broad-scale spatial patterns of landuse/landcover within watersheds can influence the outcomes of site-scale riparian restoration. Given a better understanding of terms used in the model, it could be used to help determine the length and width of riparian restoration necessary to achieve watershed management goals in different watershed settings.