Lizards or Salamanders?

The southern Appalachians are crawling with salamanders. In western North Carolina alone, more than 45 species can be found, and they are critical members of food webs – both as predators and as prey.

Salamanders and other amphibians, as well as reptiles, can be affected by forest management practices. “However, amphibians and reptiles are ecologically, physiologically, and phylogenetically distinct,” says U.S. Forest Service research ecologist Katie Greenberg. “So we might expect them to respond very differently to forest management practices.”

Managers in the southern Appalachians often want to restore oak ecosystems, and Greenberg and her colleagues studied the impact of three silvicultural treatments that may enhance oak regeneration: prescribed burning in the winter, herbicide application to the forest midstory, and a shelterwood harvest followed by a prescribed burn.

The treatments have not been widely tested on moist, productive sites where competition from faster-growing tree species such as yellow-poplar is fierce. Oak seedlings are often abundant in these sites, but then languish and die in the shady understory, never to make it into the canopy.

The study was published in Forest Ecology and Management, and took place in western North Carolina, on the Cold Mountain Game Land managed by the North Carolina Wildlife Resources Commission for wildlife. Before the plots were treated, Greenberg and her colleagues sampled reptiles and amphibians. After the treatments the scientists continued to sample reptiles and amphibians for 4 years. Over the entire study period, the scientists captured 1,530 amphibians and 269 reptiles.

“We found that terrestrial salamander abundance declined within a few years of the shelterwood harvest,” says Greenberg. “We did not see declines in sites where the midstory was treated with herbicide or low-intensity prescribed fire.” However, at least one species – the Southern Appalachian salamander (Plethodon teyahalee) – decreased on the shelterwood sites.  However, abundance also decreased in the control sites where no treatments had been applied.

The decrease in salamander abundance did not happen immediately. Depending on the site, it took 3 years before declines were detected. “Our study illustrates the importance of longer-term studies to detect changes in reptile and amphibian communities,” says Greenberg. “These changes may not be immediately apparent after disturbances.”

After the shelterwood harvest, lizards – especially five-lined skinks (Plestiodon fasciatus) – became more abundant. “Some terrestrial salamander species are sensitive to microclimates on the forest floor,” says Greenberg. “Removing the canopy may have caused changes in microclimate that favored lizards, but not the salamanders.” The different responses are probably because of their different habitat requirements and life history traits, and other research suggests effects could be long-lasting.

“Some scientists have suggested that salamanders can be used as an indicator of healthy ecosystems,” says Greenberg. “However, they might be more useful as an indicator of forest condition. For example, a recently harvested forest might be ‘unhealthy’ for terrestrial salamanders, but ‘healthy’ for other animals that prefer open, lighter conditions.”

The early successional habitat that shelterwood harvests create does not favor terrestrial salamanders. However, it does favor other species – and not just lizards. Some early successional bird species, such as indigo buntings, Eastern towhees, and chestnut-sided warblers thrive in young, open forests. Bees, butterflies, and other pollinators also do well in these open conditions. Greenberg has published several other studies on the value of early successional habitat, as well as a book on how to sustain young forests.

Read the full text of the article.

Read about how birds respond to oak regeneration treatments.

For more information, email Katie Greenberg at kgreenberg@fs.fed.us.

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