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Oregon Department of Forestry - Private Forests Program

Forest Practices Research & Monitoring Program
Riparian Function and Stream Temperature (RipStream) Study
The objective of this study is to evaluate effectiveness of forest practices rules and State Forest management strategies in protecting stream temperature and promoting riparian structure that provides necessary functions for the protection of fish and wildlife habitat. The project is evaluating both privately and state-owned forestland. On privately owned forestland, riparian management areas are being managed under forest practice rules as described in the Forest Practices Act. On state-owned forestland, riparian management areas are being managed using riparian and aquatic strategies as described in the Northwest State Forests Management Plan. This project is evaluating stream temperature and riparian condition two years before and five years after harvesting. Field work began in 2002 and was completed by 2010.
 
RipStream Analysis Results
Pre-harvest study site conditions and temperature patterns are described in the following peer-reviewed manuscript (full article):
Dent, L., D. Vick, K. Abraham, S. Shoenholtz, and S. Johnson.  2008.  Summer temperature patterns in headwater streams of the Oregon Coast Range.  Journal of the American Water Resources Association 44: 803-813.
Initial post-harvest analysis of stream temperatures relative to the Oregon Department of Environmental Quality’s permissible stream temperature change threshold, the Protecting Cold Water Criterion (full article):
Groom, J.D., L. Dent, and L.J. Madsen. 2011. Stream temperature change detection for state and private forests in the Oregon Coast Range.  Water Resources Research 47: W01501, doi:10.1029/2009WR009061.
The magnitude of temperature warming during the first two years post-harvest and relationship to changes in stream shade and other site characteristics.  The analysis also examined the relationship between shade and riparian vegetation characteristics post-harvest (manuscript):
      Groom, J.D., L. Dent, and L.J. Madsen. 2011. Response of western Oregon stream temperatures to contemporary forest management. Forest Ecology and Management, doi:10.1016/j.foreco.2011.07.012
 
 
Preliminary Analysis Results
Five-year post-harvest analysis.  Previous analyses of the RipStream data concentrated on determining the immediate effects (first two summers) of timber harvest on stream temperatures. Elevations in stream temperatures were related to declines in shade.  However, questions remained regarding the longevity of these site conditions.  How long would it take for shade to recover and temperatures to return to original pre-harvest levels?  We analyzed the full RipStream data set, including all pre- and post-harvest years, to understand how the streams responded to timber harvest over time.  We included data from all 33 sites, 15 of which were state forest sites and 18 were on private industrial timberland. There were two separate analyses for shade and temperature. The first examined shade and temperature responses over the full seven years of data collection.  The second asked, given the change between pre-harvest and first-year post-harvest conditions for individual sites, how shade or temperature responded during the full five years post-harvest. Since shade was measured every other year and not every year like stream temperature, we needed to “fill in the gaps” if we wished to examine the relationships between stream temperature (measured every year) and shade.  We filled in the missing shade values through a statistical process called imputation.  Following the data imputation, we began the full-scale analysis.  When looking at the full data set, the results indicate that stream temperatures for are best predicted by site shade levels, knowing if the site is private and in post-harvest condition, treatment reach length, and change in stream temperatures in the upstream control reach. When examining just the post-harvest stream temperatures, the temperatures were best explained by knowing what the change in temperature was between pre-harvest and the first year post-harvest and how many years post-harvest the data were taken.  Depending on the amount of initial temperature increase, stream temperatures dropped off substantially within five years post-harvest.  Shade data for the full seven years were best predicted by knowing the basal area around a stream, the amount of blowdown, whether a site was in a post-harvest condition, and the number of years post-harvest.  When looking at just the post-harvest years, it appeared that the bigger the initial decline in shade, the greater the subsequent increase in shade. We interpret these results in total to indicate that shade is controlling stream temperature, but both are on a trajectory towards recovery at five years after harvest. 

Scientific Studies

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