Document Details
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Title |
Habitat requirements of amphibians for wetland conservation under variable retention harvesting | ||||||
Author |
Wind, Elke | ||||||
Date |
2007 | ||||||
Abstract |
This proposed project contributes to knowledge gaps associated with Sustainability Program Theme 1, topic 1.4, Effectiveness of stand-level structures and habitat in maintaining biodiversity. Amphibian populations have been declining worldwide, including the Pacific Northwest. Amphibians may serve as indicator species of environmental health due to their dependence upon both terrestrial and aquatic habitats, their semi-permeable skin (that makes them vulnerable to pollutants and dependent upon moist conditions for subcutaneous respiration), and their limited movements (e.g., most remain within 500 m of the breeding site. Studies have shown that amphibians are less abundant in clearcuts compared to forests, but the results have been inconsistent. Because of their dependence on moist, cool microsites, amphibians are an excellent study group in relation to variable retention harvest methods. However, our research suggests that they cannot be effectively studied terrestrially as part of a variable retention monitoring program due to their patchy distribution and high variability across the landscape in relation to wetland sites. Wetlands are important habitat for aquatic-breeding amphibian species, but they are threatened by development, agriculture, and forestry operations. Amphibians use small wetlands (< 1 ha) for rehydration, cover, foraging, and for breeding because they offer protection from many aquatic predators such as fish that reside in permanent water. However, most small wetlands are not afforded protection under the Forest and Range Practices Act. Variable retention harvesting methods often anchor forest patches over small wetlands, effectively creating a riparian buffer. The effects of this have not been thoroughly investigated, in terms of potential impacts to hydroperiod or amphibian populations. The objective of this study is to investigate the effects of buffering small wetlands on hydroperiod and amphibian survival rates to metamorphosis under an active experimental design. This project is an expansion of a wetland buffer study Weyerhaeuser initiated in 2004 on private land in South Island Timberlands. In Weyerhaeuser?s TFL 39 and 44 on northern Vancouver Island, at least 3 mature forest stands (i.e., > 80 years) slated for harvest in winter 2007 will be selected as experimental wetland buffer study sites, using maps produced for small wetland work in 2002. Site selection will be based on stand age and type, elevation, scheduled harvest dates, and a minimum of 6 small wetlands per site. Similar ponds within each site will be grouped and randomly allocated to each treatment ? i.e., unbuffered, thin buffer (normal width), and wide buffer (2x the normal width). Ground truthing and pre-treatment data collection will be collected in 2005 and 2006?post-treatment data collection will take place in 2007. Amphibians will be surveyed visually and by using aquatic funnel traps to determine the number of species breeding at each site, and to monitor the number of species that reach metamorphosis before pond drying. Hydroperiod will be monitored by measuring the maximum water depth at the deepest point in each point at least once per week from spring (the onset of breeding) until pond drying (usually by August). General habitat features of each wetland will be recorded for treatment grouping purposes (e.g., wetland size, vegetative cover, canopy cover, etc.), and to identify characteristics of wetlands that are more likely to be impacted by forest harvesting and should be buffered (e.g., have significantly reduced hydroperiods post-harvest). | ||||||
Report Number |
FIA2007MR335 | ||||||
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