Adaptive Management for Urban Oak Ecosystem Restoration: Effects of Canopy Thinning on Seedling Regeneration and Groundlayer Plant Communities

Oak forests are complex, fire-dependent ecosystems, critical for supporting ecosystem services such as biodiversity and carbon storage. However, throughout eastern North America, previously oak-dominant ecosystems have undergone shifts in species composition and structure, primarily as a result of human influences. Land managers face the challenge of restoring oak ecosystems and promoting oak regeneration in urban and suburban natural areas, where high-intensity silvicultural treatments are often not feasible. To investigate management alternatives, an adaptive management experiment was implemented in Lake County, IL in 2012, in which five thinning treatments of varying intensity, timing, and spatial aggregation were replicated across three study areas. I monitored the survival, growth, and morphology of planted oak seedlings and quantified microclimatic responses to the overstory thinning strategies. Understory light availability, soil temperature, and atmospheric temperature differed among treatments, suggesting that overstory thinning affected understory microclimates. Even though light availability was significantly increased by canopy thinning, survival and growth of planted oak seedlings did not differ among treatments. Overall high seedling survival rates suggest that current conditions in these sites are amenable to oak regeneration even with only subcanopy-focused management. However, further monitoring will be needed to assess the potential for canopy thinning treatments to influence transitions to the sapling and canopy layers. The results of this adaptive management experiment demonstrate a lower intensity alternative to traditional even-aged silvicultural methods that could be utilized for oak woodland management and restoration in urban ecosystems and natural areas throughout the eastern U.S