Monitoring Amphibians at Redwood National Park: Design, Detection Issues and Sampling Techniques

Bury, R.; Hyde, Erin

Amphibians are a major component of the forest-floor fauna in Pacific Northwest forests and play important ecological roles (see Bury et al. 2002; Davic and Welsh 2004). Rigorous, effective sampling protocols are essential to understanding the response of amphibians and associated habitat to perturbations such as fire and timber harvest. Designs and field techniques also must be able to cover sufficient area or ranges of inference. Adequate samples are needed capture the range of variation in habitat and species assemblages over the landscape. Welsh and Droege (2001) stated that use of salamanders as bioindicators requires appropriate and cost-effective counting techniques that are precise and replicable (i.e., exhibit low count variances) and accurate (i.e., unbiased). Terrestrial salamanders are diverse and abundant in many North American forests (Bury et al. 1991; deMaynadier and Hunter 1995; Welsh and Droege 2001). Several of these species or communities are likely candidates for long term tracking within Redwood National Park as part of the National Park Service's Inventory and Monitoring Program. Redwood National Park is home to a diverse group of 14 species of amphibians and 12 species of reptiles (Table 1). Some of these can reach high densities locally (>1 m2). For example, Welsh and Lind (1992) estimated the density of the Del Norte salamander, Plethodon elongatus, at 3200-9000 per ha at one site in northwestern California. Because the core blocks of Redwood National Park represent relatively undisturbed ecosystems, they can provide excellent baseline data to monitor amphibians trends regionally (e.g., predicated global climate changes) and serve as a comparison to nearby logged stands that have suffered declines. The objectives of this paper are to evaluate sampling techniques and designs for use in future monitoring programs at Redwood National Park. There are current conflicts in employment of relative abundance (count indices) and estimations of densities (mark and recapture), but are compared elsewhere (Bury 2004). Here, the goal is a union of emerging technologies (field measurements) and statistical rigor into an effective system to best compare how populations may fluctuate over time (e.g., natural cycles), large scale changes (e.g., global climate change) or short-term effects (e.g., fire, thinning).

Monitoring Amphibians at Redwood National Park: Design, Detection Issues and Sampling Techniques

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