Influence of density reduction on growth response, stem quality, and understory dynamics in pole-size hardwood stands in the Hoosier National Forest

Ryan L Woods, Purdue University

Abstract

Without proper silvicultural management, recruitment of oak ( Quercus L. spp.) into mature stands has proven difficult amidst heavy competition from fast-growing, pioneer species. Successful oak regeneration is often limited to the stem initiation stage, where there are typically sufficient numbers of oak. As stands develop into the stem exclusion stage, oak numbers decrease due to more competitive, faster growing species such as yellow-poplar (Liriodendron tulipifera L.) and black cherry (Prunus serotina Ehrh.). A common silvicultural prescription to mitigate these effects is thinning. During the spring of 2007, a low thinning was implemented in five stands on the Hoosier National Forest in south-central Indiana that ranged from 27 to 30 years of age; treatments consisted of 75 and 60 percent stocking, as well as control plots with no thinning. We evaluated the effects of two thinning treatments on stand structure and species composition, environmental conditions, crop-tree development, and changes in understory vegetation population structure. The relative density of oak can be increased, if not maintained, by thinning from below, yet we observed only marginal changes in yellow-poplar and black cherry. Canopy openness significantly increased in the 75 and 60 percent stocking treatments, compared to the control, at the end of the two growing seasons. Mean photosynthetic active radiation in the understory was significantly greater in the 75 and 60 percent stocking treatments compared to the control in both years. Mean air and soil temperature showed similar trends, namely the 75 and 60 percent stocking treatments were consistently greater than the control throughout the second growing season. Mean soil moisture in the 75 and 60 percent stocking treatments, however, were consistently lower than the controls throughout the second growing season.

Degree

M.S.

Advisors

Jacobs, Purdue University.

Subject Area

Forestry

COinS