Research

PNW Funded Projects
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PNW Project Overview 2001

River Food Web Response to Riparian Zone Management

Principal Investigator:  
Dr. J. Timothy Wootten, Department of Ecology and Evolution, University of Chicago

Awarded: $34,764

Project Description:
The effect of watershed land use on streams and rivers is an important issue in both basic and applied ecology.  Understanding the mechanisms by which land use impacts river and the relative effects of these mechanisms is necessary to implement sound conservation, management and remediation practices.  The causes of decline in Pacific salmon stocks and their links to logging represent a recent major concern.  Aquatic food webs are critical in determining fish growth and survival, and food web components are potentially affected by changing land use patterns, yet the effects of land use on the stream communities supporting fish populations is poorly understood.  

A large scale replicated manipulation of the riparian zone along the South Fork Pysht River in conjunction with rivers in close proximity draining watersheds of different land use intensity, provides a unique opportunity both to evaluate a potential management strategy for salmon restoration, and to provide insight into how land management affects salmon populations through its effects on river food webs.  This project will focus on the effects of changing the energy base of river food webs, particularly the effects of changing algal production associated with increased light.  The study will increase our understanding of how logging activity influences aquatic ecosystems, of the interplay between the energy base and food web structure in rivers, and of the degree to which small-scale experiments can be extended to anticipate large-scale effects.  The study will also provide baseline information for understanding effects of conifer verses alder dominated riparian zones on food webs supporting salmon for comparison to data collected in the future when conifers begin to dominate the experimental riparian areas.  Futhermore, the work will shed light on a potentially unique salmon restoration strategy in which local manipulation of the productive base of river food webs in hydrologically appropriate areas in integrated within a larger-scale landscape in which the riparian corridors are conserved.

The objectives of the study are:

1) To examine the food web impacts of large-scale experimental manipulation of the riparian zone.
2) To explore the concordance of food web changes associated with small scale light manipulation experiments and large scale riparian zone manipulations.
3) To investigate the interplay between nutrient and light limitation in relation to riparian zone manipulation.
4) To compare food web patterns of rivers flowing through different land use regimes with large-scale riparian manipulations to determine the extent to which mechanisms apparent in the riparian manipulations can explain these patterns.

Project Status:
2001 funds will be distributed to projects in September 2001.

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