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A study on the effect of wetlands ecosystem restoration on amphibian population …

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Materials and Methods
- Amphibian biodiversity recovery in a large-scale ecosystem restoration

We located amphibian breeding sites and identified species at each site using standard North American Monitoring Protocols (Karns 1986; Heyer et al. 1994). We used a combination of call surveys, seines, dip-nets, minnow traps, terrestrial search and seize, and drift fences with funnel traps to increase the likelihood of detecting the presence of rare species. We conducted nocturnal frog call surveys three times each year at each natural and restored wetland. Surveys occurred during appropriate climatic conditions for the breeding season of each frog species from April through June in 1998, 2000 - 2003. We sampled each wetland with seines, dip-nets and minnow traps twice a year, once during April or early-May and once during the period from mid-May through mid-July. Habitat restoration began in 1999. Wetland were restored by plugging and filling drainage ditches, breaking drainage tiles, and scraping and recontouring soil in wetland basins to depths up to 1 m. Prairie restoration was conducted by application of herbicides, prescribed burns and planting prairie plants. Some stretches (8-12 m long) of the drainage ditches were not plugged because they harbored important native wetland plants.

We conducted terrestrial search and seizure to focus on detection of terrestrial adults and newly metamorphosed juveniles. The terrestrial search included visual searches for individuals on the ground and by searching under any cover objects that we encountered. We searched upland habitat surrounding each wetland twice each year, once during April or early-May and once from mid-May through mid-July. We used drift fence arrays to detect the presence and movement of terrestrial amphibians. We constructed drift fences from aluminum window screen to form three “arms” that extended 6 m from a common center point (Fig. 2). We placed funnel traps along the ends of each arm. Moisture and shade were provided for trapped animals. Traps were checked at sunrise each morning, and animals were examined and released. In June 2001, we established 10 drift fence arrays in four clusters. We checked the arrays six days a week from 12 June until 20 July. In April 2002 we established eight new drift fences giving us a total of 18 arrays in six clusters. Two were added to the 2001 clusters (giving a total of three arrays per cluster) and the remaining six formed two new clusters. We checked the arrays four days a week from 12 April to 5 May 2002 and every day from 6 May until 23 July 2002.

The presence of species was recorded at breeding sites each year. Abundance was estimated using an ordinal scale of frog call intensity and capture per effort. Each population was given a relative abundance index value of 1-5 according to Karns (1986) and Brodman (2003). Linear and exponential regression (α = 0.05) was used to analyze trends in the number of amphibian breeding sites, populations, relative abundance index, species richness, and percentage of occupancy of amphibians among management units from 1998-2003.

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