Dana Warren

Associate Professor, Oregon State University
HJ Andrews Experimental Forest, Oregon

I received my BS from Skidmore College and my MS and Ph.D from Cornell University. My research focuses on aquatic-terrestrial linkages and how the age stage and structure of riparian forests influence aquatic ecosystems. My work encompasses a range of topics including stream food web ecology, aquatic and riparian ecosystem dynamics, stream habitat, land-use change, wildfire and forest management.

Short- and Long-term Perspectives of Forest Management Effects on Stream Biota

In forested headwater ecosystems, streams are strongly influenced by the age, stage, and structure of streamside (riparian) forests. Historic logging practices in the Pacific Northwest region of North America often included cutting right to the water’s edge and removing stream wood. In many cases, this led to a reduction in fish abundance. However, in other cases, canopy removal led to an increase in fish abundances. This increase was attributed to greater in-stream primary production that fueled invertebrate production and in turn the production of apex predators. Contrasting responses to of fish forest management has led to differences in how people articulated and perceived the potential effects of logging for stream fish. These studies, however, generally only consider the period shortly after forest management. At the HJ Andrews Experimental Forest, we had the opportunity to return to sites that were initially assessed in the late 1970’s, shortly after forest management, in which an overall increase in fish biomass was documented after logging (relative to nearby sections of stream with old-growth riparian forests). But this was a short-term response. Since that initial study streamside forests have regrown and canopies have closed back over the stream to the point where many of the formerly logged sites are darker than the old-growth reference sites to which they were initially compared. We returned to five paired stream sites nearly forty years after the initial surveys to evaluate long-term fish responses to historic logging in these systems. In all five sites, the relative increase in fish that was documented in the 1970’s had declined, and in three of the sites, the managed stream switched from having greater fish biomass relative to is paired old-growth forest reach to having lower fish biomass than this old-growth reference site. This result was generally consistent with the change in stream canopy cover over that time period. Overall, this study highlights the importance of considering long-term processes and how the initial responses to forest management – or indeed any canopy loss along a stream – are likely change over time.


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