Forest management can be used to move secondary growth forests from low diversity, low productivity, and highly invaded states toward mixed-aged stands of diverse native woody and herbaceous species. Demographic shifts among woody species in the forest understory in response to overstory thinning and non-native species removal help determine the trajectories of forest communities following management. Here, we explore the impacts of forest management on understory dynamics in a post-agriculture mixed mesophilic hardwood forest. Specifically, we treated forest plots with one of three management treatments: 1) overstory thinning (girdling of approximately 20% of trees to open the canopy), 2) overstory thinning coupled with non-native shrub removal, or 3) unmanaged control. We monitored understory demographics of woody vegetation including seedling recruitment, mortality, and growth across 116 randomly placed meter-squared plots while accounting for changes in light availability, soil conditions, and understory composition.
Results/Conclusions
We find that over the first three years following management implementation, recruitment was higher in areas in which the overstory was thinned in tandem with invasive shrub removal (p = 0.04). These shifts in recruitment were variable across species (species:treatment p < .001). Growth rates and mortality of woody seedlings, however, were relatively stable across forest management treatments (growth rates: p = 0.95; mortality: p=0.45), though mortality rates were variable from year to year (p = 0.05). Shifts in recruitment across species within the forest understory will be key driving forest responses to management and setting up trajectories for future forests, and while growth and mortality seem generally resilient to management effects, their variability across years leaves space that treatment impacts may be revealed only under certain environmental conditions.
