Amphibians as Indicators of Wetland Habitat Conservation under Variable Retention Harvesting

This project built on an existing long-term study investigating the effects of forest harvesting on small wetlands habitats and associated aquatic-breeding amphibian populations. In 2003, we initiated a preand post-harvest experiment at three study sites with 70+ small wetland habitats less than 1 ha in size in the Nanaimo River Watershed to investigate the effects of forest harvesting on the hydroperiod and presence of breeding amphibians. Pacific Treefrogs, Redlegged Frogs, and Long-toed Salamanders occurred in numerous wetlands within the three study sites, including many relatively small wetlands (e.g., 0.003 ha). Results to date suggest that: 1) there are species-specific habitat requirements that affect where amphibians breed (e.g., Redlegged Frogs breed in only a few small wetlands); 2) amphibians continue to reproduce in wetlands within cutover areas initially after harvesting; and 3) at least two of the species appeared to exploit previously unoccupied wetlands due to changes in the habitat characteristics (e.g., decreased canopy cover). The survival of young in cutblocks is a concern (e.g., sink habitats). However, our results to date indicate that in-pond conditions may not be limiting as the small wetlands experienced longer hydroperiods initially after harvest due to a combination of increased water depths and slower drying rates. In addition to the findings of our research, we recognized a number of management issues in relation to small wetlands in landscapes managed for timber production that related to mapping and site-level operations (e.g., infilling, location of roads). The ability to effectively manage these small wetlands lies in the hands of the individuals that walk proposed blocks (e.g., engineers), as most wetlands less than 1 ha in size cannot be identified from air photos. However, we also observed that variable retention harvesting methods often anchored retention patches over small wetlands, usually the largest of these small wetlands, inadvertently providing a riparian buffer. Even small amounts of riparian retention appeared to help protect the quality of the in-pond environment. From these observations, we determined that there was information that could be provided to forestry field personnel that could help them allocate potentially limited retention resources in the most beneficial way for amphibians (e.g., beyond wetland size). Based on our observations and research results to date, the question we had with respect to this FIA/FSP study was: What factors influence where pond-breeding amphibian species reproduce and can this information be packaged in such a way so that forestry field personnel working on proposed blocks can identify and prioritize ponds for retention? The purpose of this study was to create a user-friendly wetland assessment card for forestry field personnel that could be used to help them identify and assess potential amphibian breeding ponds that should be considered for retention. This was accomplished by utilizing the existing pre-harvest data set from the long-term monitoring sites located in the Nanaimo River watershed. Habitat analyses indicated that wetland size, canopy cover, and in-pond vegetation were important factors influencing amphibian breeding pond selection. The field card was field tested by E. Wind and volunteer foresters and technicians in 2007 to ensure that it was user-friendly and effective before a final version was produced. Field testing consisted of a comparison of results from amphibian breeding surveys to those from assessments from foresters using the field card only. Approximately 50% of wetlands with confirmed breeding had similar ratings between the amphibian surveys and the field card assessments. However, over 70% of wetlands matched or had an upward versus downward ranking between the two assessment methods, and 71% of Red-legged Frog wetlands matched field card assessments and were ranked as having a high probability of breeding (i.e., should receive retention). Based on the assessment results and recommendations made by the volunteer foresters via a field card evaluation form, a new, final version of the field card was produced, extensively promoted, and distributed to foresters on the south coast in 2008.