Testing the effect of restoration‐focused silviculture on oak regeneration and groundlayer plant communities in urban–exurban oak woodlands

Abstract

Throughout their global range, oak‐dominated ecosystems have undergone state changes in stand structure and composition. Land managers face an especially acute challenge in restoring oak ecosystems and promoting oak regeneration in urban–exurban areas, where high‐intensity silvicultural treatments are often not feasible. To investigate low‐intensity management alternatives which could be widely applied in urban–exurban forests, a large‐scale adaptive management experiment was implemented in Lake County, IL, in 2012. Five canopy manipulation treatments of varying intensity, timing, and spatial aggregation were replicated across three study areas and oak seedlings were under‐planted into treatment units following management. Responses of understory light environment, shrub and groundlayer plant communities, and survival and growth of underplanted oak seedlings were evaluated. Understory light availability, canopy openness, total groundlayer plant cover, and groundlayer species diversity all differed among treatments. However, although understory light availability was significantly increased by canopy manipulation, groundlayer communities and oak seedling survival and growth did not differ among treatments. High overall seedling survival rates suggest current conditions are amenable to oak regeneration, but long‐term monitoring will be needed to assess the potential for seedlings to transition to the sapling and canopy layers. Early results demonstrate that canopy‐focused silvicultural treatments can affect the understory light environment and, to some degree, groundlayer plant communities. However, underplanting of oak seedlings paired with subcanopy thinning may be sufficient to restore an oak seedling layer, and (when necessary or preferred) canopy manipulation could potentially be deferred until later in the restoration timeline to promote oak recruitment.

Convergence and divergence in science and practice of urban and rural forest restoration

“…Johnson & Handel, 2016). Long‐term studies have begun to provide a better understanding of alternative planting strategies, such as controlling initial species composition and functional diversity (Robinson & Handel, 2000; Oldfield et al ., 2015), broadcast seeding and enrichment plantings (Laughlin & Clarkson, 2018), canopy manipulations (Pastick, Maurer & Fahey, 2021), and the potential for natural regeneration (Wallace, Laughlin & Clarkson, 2017; Piana et al ., 2021 a ). Collectively, these approaches are improving understanding of forest recovery potential, management regimes and timeframes for restoration (e.g.…”

Climate adaptation actions for urban forests and human health

“…364 ► Restore or create conditions that allow tree seedlings to thrive by removing nonnative species in the shrub layer and canopy trees while controlling herbivory. 365,366 ► Implement silvicultural practices to reduce competition around large, long-lived trees to maintain tree health, such as thinning dense stands from below or using prescribed fire in fire-adapted ecosystems.…”

Climate Adaptive Silviculture for the City: Practitioners and Researchers Co-create a Framework for Studying Urban Oak-Dominated Mixed Hardwood Forests

“…In cities, canopy removal is usually not viable because of public resistance to cutting trees, but also because of ecological concern of an already high rate of canopy loss from drought, exotic insects and disease, limited forest area, and high public visibility. Silvicultural techniques need to be tested that include this context and then evaluated for efficacy and acceptability (Pastick et al, 2021). Furthermore, deer, altered site conditions, and invasive plants may also limit oak regeneration and recruitment even when light and site treatment is no longer a limiting factor.…”

“…Inspired in part by the experimental forests, a growing body of work examining specific dynamics of forests in urban settings provides the basis for urban silviculture (Schuler and Forrest, 2008;Pregitzer et al, 2019a;Sonti et al, 2019;Piana et al, 2021b;Zukswert et al, 2021). Also, at a broader scale, frameworks are being developed for adapting urban forests to climate change (e.g., Brandt et al, 2016) and efforts are emerging in other cities that test silvicultural strategies to adapt to a changing climate (e.g., Hammes et al, 2020;Pastick et al, 2021). Even so, there are few urban forestry studies covering a time span necessary to understand forest stand dynamics (Oldfield et al, 2013) and no applied forest management studies replicated across multiple cities.…”