Friday, August 6, 2010

PS 103-110: Effect of high-intensity directed fire on survival of three invasive species: Paulownia tomentosa, Ligustrum sinense, and Lonicera maackii

Jeanette R. Williams, Alabama A&M University and Luben D. Dimov, Alabama A&M University.


         Invasive herbaceous and woody species are of growing concern.  Invasive species hinder forest use, management activities, and degrade diversity and wildlife habitat.  Chinese privet (Ligustrum sinense), Amur honeysuckle (Lonicera maackii), and royal paulownia (Paulownia tomentosa) are three of the most common invasive woody plant species in the North Alabama region.  There are numerous techniques for their control, but many are not environmentally friendly and are time consuming to apply.  High-intensity directed fire at the base of the stem was used to test its effectiveness in killing each of the three species and preventing them from resprouting from the stump. The source of the fire is a torch with propane-powered flame. We tested the effectiveness of this technique three times during the year - winter, early spring, and summer. Each season we treated 100 stems of Chinese privet (50 in each diameter class – 0.5-1.9 inches and 2.0-4.0 inches) and Paulownia (approximately 50 in each diameter class 8.0 inches and below and above 8.1 inches) and 200 honeysuckle stem groups.  We examined post-treatment mortality, counted the number of new stump sprouts, burned the new sprouts, and checked for mortality and sprouting after the second burn.        


         Our preliminary results are for the response to winter and spring burns. In Amur honeysuckle the pre-treatment number of stems in a stem group was strongly correlated with the number of sprouts after the burn (R2 = 0.56, p <0.0001). The positive parameter estimate for the slope indicated that as the number of stems increases the number of sprouts after a burn increases as well.   The percent stem mortality in a stem group was significantly higher in the treatment group than in the control (p<0.0001). Chinese privet experienced post-treatment mortality in both diameter classes for the spring burn, but no mortality was found after the winter burn in the 2.0-4.0 diameter class. One and a half months into the growing season, Paulownia tomentosa showed no mortality following the winter and spring burn.