Distribution and demographics of Ailanthus altissima in an oak forest landscape managed with timber harvesting and prescribed fire

Abstract

Ailanthus altissima ((Mill.) Swingle, tree-of-heaven), an exotic invasive tree that is common throughout much of the eastern United States, can invade and expand dramatically when forests are disturbed. Anecdotal evidence suggests that fire facilitates its spread, but the relationship between fire and this prolific invasive tree is poorly understood. To better understand the impacts of fire on Ailanthus, we conducted studies at Tar Hollow State Forest in southeastern Ohio, where Ailanthus is widely distributed and where, since 2001, prescribed fire has been applied to 25% of the 3885-ha study area. Our objective was to gain a better understanding of how the distribution and abundance of Ailanthus is related to recent fires, harvesting activity, and site characteristics. We quantified the abundance and demography of Ailanthus, as well as prescribed fire, harvesting, aspect, slope, and available light, using a systematic grid (400m) of sample plots (N=267). From these data, we identified time since last timber harvest, not prescribed fire history, as the major driver of both Ailanthus seedling and tree presence and density. Two site factors, aspect index (a transformation of aspect) and photosynthetically active radiation, were also significant predictors of seedling presence or density. These findings to demonstrate that dormant-season prescribed fire has a limited impact on the distribution of Ailanthus within forested landscapes and that recent timber harvesting (within 20years) is the primary predictor. Thus, care in harvesting to prevent soil disturbance and spread of Ailanthus seed is paramount when managing for this aggressive species.