Effects of prescribed burning and cutting on a non-native invasive liana, Oriental bittersweet (Celastrus orbiculatus Thunb.)

Background/Question/Methods

Prescribed burning is often used as a management tool in the central and eastern U.S. to control invasive plants, particularly woody invasives in grasslands, savannas, and oak woodlands.  However, little is known about the effects of burning on the non-native invasive liana, Celastrus orbiculatus.  The success of C. orbiculatus invasion is likely due in large part to its high reproductive capacity owing to heavy seed set and prolific root suckering.  Though seed rain can be heavy, seed viability drops significantly after the first growing season, leaving a “seedling bank” but very minimal seed bank.  This study was conducted in an oak savannah/woodland in Madison, Wisconsin, USA.  Given the life history of C. orbiculatus, it was hypothesized that in experimental plots where the larger vines were cut a year prior to burning to minimize post-fire seed rain, the fire would damage the “seedling bank” and small, non-reproductive vines enough to control its spread.  These plots were compared to burned plots where reproductive vines were not cut and to unburned plots with and without cutting of mature vines.  Percent cover, number of established stems, and seedlings of C. orbiculatus were recorded during summer 2011 and plots were resampled in summer 2012 following a spring burn.

Results/Conclusions

Results from vegetation sampling conducted during the first growing season after the fire suggest that prescribed burning might not be an effective control method for C. orbiculatus, at least not in areas where prescribed fires tend to be patchy and low-intensity.  Neither percent cover of C. orbiculatus nor the number of established stems was significantly reduced in burned plots compared to conditions during the growing season preceding the prescribed burn.  Seedling recruitment in the summer following the burn was greatly reduced across all plots, apparently related to the abnormally dry conditions rather than any effect attributable to the cutting or burning treatments.  Given the minimal negative effects of burning on C. orbiculatus survival, this study suggests that fire alone is not the most effective means of controlling this invasive vine. Sampling of these research plots in subsequent growing seasons will reveal whether the burning might actually increase spread of C. orbiculatus due to reduced cover of competitors and/or increased root suckering on stems damaged by the fire.