Amphibian colonization of new habitat: If you build it, they will come.

摘要

In 2003, Wilson Creek running through Bernheim Arboretum and Research Forest in central Kentucky was restored to its original winding path through a valley field. Early 20th century settlers had previously redirected this creek to run a straight path along the eastern hillside in order to maximize the valley for farming.{09}As part of the restoration to its pre-settler path, seven ponds were created in the corridor of the old streambed, which created habitat for pond-breeding amphibians. Sampling began one year after construction was complete, and over two years the amphibian assemblages of these ponds were compared to those of five ponds >30 years old. All six backwater ponds and three upland forest ponds per year were visually assessed and dip-netted for any amphibian life stage: egg, larvae or adult. In addition, 15 mostly ephemeral pools also created from the restoration were monitored for species richness only. The physical characteristics of all permanent ponds were also described by their perimeter size, maximum water depth, elevation, and distance to a forest edge. They were also sampled twice a year for various water chemistry parameters: nitrate-nitrite, ammonia, total nitrogen, soluble reactive phosphorus, total phosphorous, pH, silica, chlorine, dissolved organic carbon, total suspended solids, turbidity, and conductivity. Fourteen amphibian species were recorded in all, but only eleven species were found in the backwater ponds. Two species documented from all of the mature ponds and in only one of the backwater ponds were Rana sylvatica and Ambystoma jeffersonianum. Other species that were documented in the older ponds but were in low numbers in the new ones were Ambystoma maculatum and Notophthalmus viridescens. The hypothesis that older upland forest ponds would have higher species richness and higher capture rate (i.e., abundance) than the backwater ponds was supported. The hypothesis that the backwater ponds would increase in species richness from 2005 to 2006 was supported, but capture rate did not increase significantly. The ephemeral pools housed mainly H. chrysoscelis and B. americanus and may be significant breeding habitat for H. chrysoscelis . With regards to the physical parameters, the backwater ponds were significantly closer to a forest edge and lower in elevation. They did not have significantly different perimeter sizes or water depth, but they were slightly larger and shallower. The backwater ponds may be experiencing a slight edge effect, thereby being less attractive to some amphibian species. The water chemistry variables pH and conductivity were significantly higher in the backwater ponds compared to the upland forest ponds. These factors may be partially correlated with the lack of certain species, but the values for the physical and chemical parameters are within range to support healthy amphibian populations. When considering future restoration projects, a combination of permanent, semi-permanent and ephemeral pools should be considered to support the greatest diversity (i.e., highest species richness and abundance) of amphibian species. Time is needed for the new ponds to come to ecological equilibrium and be colonized by sustainable breeding populations of amphibian species. New species arrived even three years after construction of the ponds was complete and they still did not contain the level of species richness of the older, established ponds. More than four years of monitoring are needed to determine success of a restoration project that includes creating pond-breeding amphibian habitat.