Many studies have documented the establishment and spread of non-native invasive shrubs throughout eastern hardwood forests. Invasives have been shown to have large but not always consistent impacts on ecosystem dynamics. The goals of this study were to describe the temporal differences in leaf litter deposition of invasive and native woody plants, to observe the differences in nitrogen and carbon inputs between the two, to compare relationships between plant community composition and structure with leaf litter production, and to set a framework to study the long-term effects of invasive species on forest soils. We established paired plots in an oak-dominated suburban old-growth woodlot with a dense understory of non-native shrubs and removed all the non-native shrubs from one of each of the paired plots, leaving the other as a control. Woody vegetation was sampled in each plot and leaf litter traps were installed in the spring of 2009. Leaf litter was collected from the traps once a week between October-November 2009. Weekly leaf litter collections were sorted and weighed by species and by plot. Subsamples of leaves were ground and analyzed for carbon and nitrogen concentrations. These concentrations were used to budget nutrient inputs for the leaf litter of each species.
Results/Conclusions
The average woody invasive biomass removed from the treated plots was 3433 kg ha-1 (SE = 834). Despite the abundance of invasive shrubs in the forest understory, their leaf litter was only 3.47% of the total inputs, yet comprised 78.35% of the total inputs from shrubs. Removal of invasive shrubs did not significantly affect the total quantity of leaf litter inputs in the traps. Interspecies variability was quite high, yet the invasive species as a whole dropped their leaves one week later on average, implying longer photosynthetic periods and reduced light to the forest floor. This research has implications for the restoration of sites that have been invaded by non-native shrub species and for the understanding of changing forest ecosystem processes.
