Effects of turf, leaf litter, and soil compaction on emergence and establishment of invasive glossy buckthorn (Frangula alnus)

Abstract

Perennial invasive plants can be controlled by damaging established vegetative individuals or by preventing establishment of new plants from seed. Less information is available about the latter. We examined how seedling establishment of glossy buckthorn (Frangula alnus), a non-native shrub that invades forests in eastern North America, is affected by four soil surface treatments – grass-dominated turf, oak leaf litter, pine leaf litter, soil compaction – relative to an untreated control (tilled soil). Data on seedling emergence, survival, growth, and reproduction were collected from 1.5 m2 plots (six per treatment) over two years at the Kingman Research Farm, Madbury, NH, USA. Overall, buckthorn success from seed was inhibited by grass turf and facilitated by oak litter, while pine litter effects were complex and soil compaction had no effect. Specifically, relative to control, the turf treatment reduced buckthorn seedling emergence (year 2 only), increased mortality over two years, reduced density of living buckthorn, and prevented fruiting. Oak litter resulted in greater buckthorn seedling height relative to control, while pine litter, although reducing seedling emergence (year 1 only), increased both seedling height and the proportion of plants fruiting in year 2. Across all treatments and control, buckthorn seedling emergence was greatest in June, declining thereafter. Of the four treatments, only grass turf offered some promise of resisting invasion. The mechanism of resistance by turf is not known, but likely involves either more intense competition or higher levels of herbivory associated with turf. The mechanism, as well as the logistics and cost of turf establishment in logged areas, require further exploration.