Planted green ash (Fraxinus pennsylvanica Marsh.) and herbaceous vegetation responses to initial competition control during the first 3 years of afforestation

Formerly row-cropped bottomland sites that have been planted with hardwoods through afforestation programs are typically associated with low tree stocking, slow tree growth, and an enduring influence of agricultural weeds in the herbaceous stratum. Consequently, many of the intended benefits of a forestry land use are delayed or forfeited. This study evaluates the growth of planted green ash and the development of volunteer herbaceous communities on a bottomland site in southern Illinois, USA in response to two different operational herbicide (pre-emergence sulfometuron and post-emergence glyphosate) and tillage treatments, applied individually and in combination. Both herbicide treatments increased green ash height and diameter growth while tillage produced no response. At the end of three growing seasons, the post-emergence glyphosate treatment increased forb cover. Total grass cover was not impacted by herbicide treatments after the second growing season. During the second and third growing seasons, the pre-emergence sulfometuron treatment increased broomsedge (Andropogon virginicus L.) cover and decreased goldenrod (Solidago nemoralis Ait.) cover relative to post-emergence glyphosate and no herbicide treatments. Johnsongrass (Sorghum halepense L.) cover decreased dramatically following the first growing season in all treatments. Horseweed (Conyza canadensis L.) exhibited a complex response to silvicultural treatments through the course of the study. Commonly used silvicultural treatments that yielded similar and positive tree growth responses differed in their impact on herbaceous community composition through the first 3 years of stand development. These results suggest that treatment choice may have long-term implications for overstory canopy development on these and similar afforested bottomland sites characterized by presence of agricultural weeds and low tree stocking.