Evidence for Negative Impacts on Terrestrial Salamanders following Invasive Plant Removal

Abstract

Invasive species are widely believed to be a major threat to biodiversity. Therefore, invasive species control is a common practice among land managers. However, the impacts of invasive species control on nontarget organisms are often unknown. To examine the impact of invasive plant removal on a functionally important, but often overlooked, group of organisms, we carried out a field experiment focusing on terrestrial salamanders. Using coverboards, we monitored the occurrence of terrestrial salamanders (primarily Northern Ravine Salamanders, Plethodon electromorphus) in forest plots where invasive plants had been experimentally removed compared with control plots where removal did not occur. We replicated this design at three study sites and sampled coverboards over 3 yr (2016–2018; 2,187 sampling events). We also undertook a laboratory experiment exposing Northern Two-Lined Salamanders (Eurycea bislineata) to native and invasive plant root extracts compared with a plain water control. Results from occupancy modeling and other analytical techniques indicated strongly reduced occupancy of P. electromorphus in plots where invasive plants were removed, compared with controls. This pattern varied among study sites but was strongest at the most heavily invaded sites. Results from the laboratory exposure study showed no significant differences in response to root extracts from native versus invasive plants. Together, these data suggest that some terrestrial salamanders may not be negatively impacted by invasive plants and that invasive plant removal, when not accompanied by native plant restoration, may have unanticipated negative effects on terrestrial salamander populations.