Effects of forest removal on amphibian migrations: implications for habitat and landscape connectivity

Leave coarse woody debris in forests

A replicated, controlled study in 2004–2007 of four seasonal wetlands in pine forest in southeastern USA (Todd et al. 2009) found that migrating amphibians used clearcuts where woody debris had been retained more than where it had been removed. By the final year, the proportion of both salamander species emigrating through clearcut with woody debris retained was significantly higher than in clearcut without woody debris (0.2 vs 0.1). The same was true for immigrating Southern toads Bufo terrestris (0.3 vs 0.1) and frogs Rana spp. (0 vs 0.5). There were four wetland sites, each surrounded by four randomly assigned treatments extending out 168 m (4 ha): partial harvest (15%), clearcut with or without coarse woody debris retained and unharvested. Harvesting was undertaken in spring 2004. Immigrating and emigrating amphibians were captured using drift-fencing with pitfall traps from February 2004 to July 2007.

(Summarised by: Rebecca K Smith)

Thin trees within forests

A randomized, replicated, controlled study in 2004–2007 of four seasonal wetlands in pine forest in southeastern USA (Todd et al. 2009) found that migrating amphibians tended to use thinned forest a similar amount to unharvested forest and that emigrating salamanders, but not frogs, used it more than clearcuts. Proportions of immigrating amphibians and emigrating frogs did not differ between treatments. The proportion of salamanders combined Ambystoma spp. and mole salamanders Ambystoma talpoideum that emigrated through thinned forest (0.2–0.4) was similar to unharvested forest (0.4–0.5) but significantly higher than clearcuts (0.1–0.2). Significantly higher numbers of ornate chorus frogs Pseudacris ornata emigrated through partial harvests than unharvested forest. Significantly more emigrating salamanders, frogs Rana spp. and southern toads retreated from clearcuts compared to partial harvests and unharvested sites. There were four wetland sites each surrounded by four randomly assigned treatments extending out 168 m (4 ha): thinning (15% removed), clearcut with or without coarse woody debris retained and unharvested. Harvesting was undertaken in spring 2004. Amphibians were captured using drift-fencing with pitfall traps from February 2004 to July 2007.