Although destruction and degradation of habitat is the leading contributor to global amphibian declines, there is a lack of information on the responses of terrestrial life-stages to habitat modifications. Knowledge of juvenile dispersal remains one of the greatest unknowns in accurately assessing impacts of land use on population abundance and persistence. Dispersing juveniles play a vital role in recolonization by moving between isolated pools. Effects of land use such as decreased forest canopy have the potential to impede juvenile dispersal through increased desiccation risk and mortality. To determine juvenile dispersal success in forest habitats modified by land use, we established four experimental forestry treatments which emulate typical regional forestry practices; a control, a partial cut, a clearcut with high coarse woody debris (CWD), and a burned clearcut with low CWD. We replicated the experiment at two ponds in upland oak-hickory forest in the Ozark Border region of Missouri. Juvenile dispersal of habitat generalist green frogs (Rana clamitans) and forest associated spotted salamanders (Ambystoma maculatum) provided examples of contrasting life histories. We individually marked recently metamorphosed amphibians as they emerged from their natal pond. Drift fences encircling ponds provided initial captures and additional drift fences recaptured amphibians in terrestrial habitat at distances of 20 m and 50 m to determine dispersal success.
Results/Conclusions
Comparisons of recaptures in the four treatments revealed significantly more green frog juveniles were captured in the control (32.8 %) and partial cut (14.9 %) than in either the high CWD clearcut (2.2 %) or low CWD burned clearcut (4.0 %). For dispersing juvenile spotted salamanders distance from pond was most important, with significantly fewer individuals captured at 50 m than 20 m in all treatments except the partial cut. The sharp decline in salamander recaptures after 20 m in the clear cuts suggests dispersal through such altered habitats is greatly reduced. Understanding juvenile dispersal is important for the development of effective amphibian conservation strategies. Ultimately information from this research should aid policy makers and land managers as they continue to seek the sustainable balance between the need for forest products and preservation of biodiversity.
