Oaks are keystone species in midwestern US ecosystems, shaping and flora and fauna species assemblages, but have been facing decline in recent years due to land use change, invasive species, and shifts in climate regimes. In addition to reductions in oak habitat, recruitment of oak seedlings into the understory has also decreased significantly due to competition by more mesic species such as maples. In the Chicago Wilderness Region only 17% of historical oak ecosystems remain, much of which is considered degraded with low oak regeneration. Management techniques such as canopy thinning and prescribed burning have been widely implemented across the region with the goal of promoting successful oak seedling recruitment into the understory. However, most management and monitoring has targeted promoting the oak seedling and sapling pools and little attention has been given to how these management practices impact the established trees. We collected tree-core samples from seven sites across the Chicago Wilderness Region to assess the effects, if any, that these management practices has on mature oak growth.
Results/Conclusions
We collected increment cores from 149 oak trees (Quercus)from 21 plots across 7 locations in the Chicago Wilderness Region. Major species sampled were Quercus alba (41%), Quercus rubra (29%), andQuercus velutina (21%). These sites varied in soil texture, but all had active restoration management of burning, thinning, and their combination as well as unmanaged controls. The sampled tree ages ranged from 24 to 246 years and diameters ranged 17.1 to 104.2 cm. We used a random effects model to assess the last decade of growth across different treatments and soil types. Both burning and soil texture were significant predictors of tree growth (p < 0.05), but thinning was not. Burning treatments resulted in a 43% decrease in growth compared to control sites. For soil texture, silty soil texture increased growth by approximately 40% relative to sandy soils. Analysis of tree growth will be combined with analysis of climate sensitivity and detailed soil geochemistry data to quantify the ecosystem impacts the current management strategies have on established seed trees. This will provide direction for management strategies that can both stimulate oak seedling establishment while ensuring the vitality of the mature, seed-producing trees.