Interactions between forestry practices and the physical and biological processes occurring in small streams are numerous and potentially complex, and there exists a relatively large body of literature, consisting of studies conducted primarily in coastal regions, that has shown how streamside timber harvesting can affect the physical habitats of streams and their fish populations. For example, scientific studies conducted in coastal regions have shown forestry practices to have deleterious effects on fish and their habitat (through decreased habitat complexity, and increased sedimentation, temperatures, and habitat instability), although beneficial effects can also occur (through increased food supply and more efficient prey capture leading to increased growth). During the course of our prior research, we monitored two small, lake-headed S3 streams prior to (1997) and following (1998-1999; 2001) a novel streamside timber harvesting treatment (which comprised the removal of all commercial timber within the riparian reserve zones while retaining non-commercial coniferous trees and deciduous vegetation), and compared these to a forested control stream. We found that summertime stream temperature changes following logging (whereby the canopy cover was reduced by ~ 50%) were relatively modest (< 1 °C) when compared to results reported in the literature for headwater streams (5-7 °C). Furthermore, the novel logging treatments did not result in detectable changes in rainbow trout (Oncorhynchus mykiss) stress levels (assessed by examining a variety of physiological response variables) or in long-range movement patterns, whereas the emergence of trout fry was earlier (and their size greater) in the logged streams when compared to the control stream. Lastly, when compared to pre-harvest levels, summertime trout densities were lower during the first post-logging summer, but higher during the second post-harvest summer. Further details of the above studies can be found in Mellina et al. (2002, 2005a, 2005b). The current research was implemented to assess post-logging stream invertebrate drift, as well as trout diet, energy allocations, and growth responses in these same streams, to gain a more complete understanding of the impacts of timber harvesting around small sub-boreal streams. Policy makers and resource practitioners (fisheries managers and foresters alike) will be able to use the results from this study to make scientifically defensible management decisions. Fisheries managers will be better able to determine which streams can support a more aggressive level of streamside harvesting (without negatively affecting resident fish species), and which streams will continue to require the protection now afforded under the FPC. Forestry planners, on the other hand, will have comprehensive evidence to present to regulatory agencies to propose changes that may be warranted to the new results-based Forest and Range Practices Act regarding harvesting practices. Based on the results from our previous research, our industry partner (CanFor) has already begun considering ways to adapt their management practices, and we anticipate that within the next few years the results from this study will lead to improved resource management planning, reduced operating costs, and a greater understanding of the responses of stream ecosystems to forest harvesting practices.
Scott Hinch, Eric Mellina, and R. Dan Moore.
Hinch, Scott G., Mellina, Eric; Moore, R. Dan. 2006. Stream invertebrate and rainbow trout bioenergetic responses to clear-cut logging in north-central British Columbia. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report