Underplanting to sustain future stocking of oak (Quercus) in temperate deciduous forests
Oaks (Quercus spp.) are one of the most important tree taxa in the northern hemisphere. Although they are dominant in mixed species forests and widely distributed, there are frequent reports of regeneration failures. An adequate population of large oak advance reproduction is a critical prerequisite to successful oak regeneration, and hence sustainability of oak. But, many oak forests lack sufficient density of large and competitive oak advance reproduction. Artificial regeneration of oak by underplanting is done to supplement natural populations of oak seedlings or to introduce oak in stands where it is missing. Planting high quality seedlings is important. Silvicultural practices that regulate stand density such as thinning and the shelterwood method are needed to increase oak's regeneration potential by promoting accumulation and growth of natural and planted seedlings before the final regeneration harvest. Control of competing vegetation and herbivory are important elements in the regeneration prescription. Light in the understory is a limiting factor to the accumulation of large oak advance reproduction. Light levels (20-50% +) sufficient for biomass production in oak reproduction result through management of stand density and other competing vegetation. We review and synthesize the literature on silvicultural approaches to using artificial regeneration to obtain successful oak regeneration that is grounded in fundamental principles of oak biology and ecology. Principles of oak regeneration presented here may also have relevance to other hydric, mesic and dry-mesic forest environments.