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Ecology and management of riparian - stream ecosystems: a large-scale experiment using alternative streamside management techniques
Marczak, Laurie B.
The management of small streams remains a controversial and high priority topic (1.1). This information is needed for government, industry, NGO and others concerned about forested watersheds. Small streams and their riparian areas provide important ecosystem services to downstream areas, control the supply and quality of water, sediment, and nutrients, as well as providing unique habitats. This study provides critical tests of the effectiveness of alterative types of riparian management for stream and riparian protection. The study includes two phases, the first of which began in 1996 to test the effectiveness of fixed width reserves of either 10 m or 30 m width versus clearcuts and control (forested) sites (13 streams in total). The second phase began in 2002 with the inclusion of an additional 3 streams to receive partial (50%) tree removal (by basal area) in the riparian areas compared to the original 3 control streams. The third aspect is the integration of all component projects into ecosystem models that will provide tools to evaluate the ecological effects of various forest management prescriptions. Phase I ? Continuation of evaluation of fixed width reserves: This project was initiated in 1996 to evaluate the effectiveness of fixed-width riparian buffers (either 30 m or 10 m wide) to protect aquatic organisms (incl. fish) and aquatic habitat, riparian organisms, and water quality, in contrast to controls and clearcuts to the streamside (Kiffney, Richardson & Bull 2003). Attributes are measured for both streams (fish, algae, organic matter, invertebrates [including crayfish], geomorphology, temperature, turbidity and chemistry, discharge, and hydrologic flow paths) and their riparian areas (amphibians, vegetation, windthrow, microclimate, terrestrial invertebrates, and small mammals). The project uses a replicated (n = 3 or 4), before-after control-impact (BACI) design to assess the effects of four treatments (clearcut with 0 m, 10 m, and 30 m buffers, and 50% partial cut to streambank) on a variety of stream and riparian components and processes. Thirteen sites (controls and clearcuts with 0, 10, or 30 m buffers) have been studied extensively during their initial perturbation (late 1998) and are showing signs of recovery in some attributes during this post-treatment period. Even after 5 years there is still broad divergence of conditions for treated streams and riparian areas, even with 30 m reserves, from the controls and pretreatment conditions. Consideration of the recovery potential, pathways, and rates will be vital to building the dynamic components of forest management into our thinking about stream and riparian management. Phase II ? partial harvesting of riparian 'reserves': We propose to measure the effectiveness of partially harvested 'reserves? (50% basal area removal) for the protection of aquatic life, riparian dependent species, water temperature, turbidity, and chemistry in coastal British Columbia. We have collected 2+ years of pre-treatment data to date for several system attributes in the stream and riparian areas of those streams whose watersheds are to be partially harvested. Estimates of watershed area were used to delineate cutblocks and harvesting was initiated in September 2004, and should be complete by the end of the year. The 6 streams (3 control, 3 partial harvest) have been chosen to reflect the natural range of variation for small streams in coastal BC. Cross-component comparisons and modelling. We have studied a large number of components of the stream and riparian systems in our study sites, and now we have the ability to compare the magnitude of impacts on each of the components. This will form a project to be undertaken by a post-doctoral fellow soon to be hired. Path analysis ? we can compare alternative hypotheses about the mechanisms of impacts by using path analysis and other means to evaluate how system responses are mediated. Indicators ? There are a wide range of potential ...
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