Effects of Mid-rotation Management on the Spread of Invasive Sericea Lespedeza in Working Pine Forests

Relatively little research has focused on the spread of sericea lespedeza (Lespedeza cuneata) in working pine forests of the southeastern United States despite sericea being one of the most prominent forest invaders of this region. Timber thinning is commonly used to meet forestry and wildlife habitat objectives within these forests, with thinning intensity being objective-dependent. Higher-intensity thinning may facilitate the spread of sericea or other forest invaders due to effects such as increased availability of understory sunlight and understory disturbance, though the degree to which this effect could be mitigated by common management practices is unclear. We compared the probability of sericea occurrence along transects in loblolly pine (Pinus taeda) stands in central Georgia treated with early growing season prescribed fire, herbicide application, and differing levels of thinning intensity to assess the effects of common mid-rotation silvicultural practices on sericea spread. We found that sericea was generally uncommon and never a major component of the understory vegetation in our study area. We found no indication that thinning intensity affected sericea spread, potentially due to the historical lack of sericea planting or invasion in the study areas. When present, sericea was reduced in the first growing season post-treatment by early growing season burns and broadcast herbicide (metsulfuron-methyl and imazapyr) application, but only the herbicide mixture provided multiyear
control. While sericea is a problematic invasive species in Southeastern forests, our results suggest that timber thinning intensity and common management actions are unlikely to promote sericea spread in working pine forests.