Long-term response of a temperate forest community to prescribed burning and thinning

Abstract

Temperate deciduous forests of eastern North America are undergoing a long-term compositional shift from oak/hickory-dominated forests to maple/birch-dominated forests, resulting in decreased species diversity and more homogeneous understory communities. This shift is likely due to secondary regrowth after extensive logging and intensive fire suppression efforts that together allowed shade-tolerant but fire-intolerant species to flourish. Managers have more recently sought to use forest management practices to counteract this shift. Our aim in this study was to improve understanding of how prescribed burning and mechanical tree thinning shape forest communities and the extent to which they favor declining species and communities of temperate eastern deciduous forest. We conducted our study at Fort Indiantown Gap National Guard Training Center in south-central Pennsylvania. Prescribed burning and mechanical thinning have been conducted onsite since 2003. Forestry plots were surveyed in 2003 just prior to management implementation and again about ten years after intensive management began, during 2013-2014. The data collected at forestry plots, including number of stems, tree diameter at breast height, management activities undertaken at the plot, and other environmental characteristics were analyzed using model selection and generalized linear mixed models. A broader community analysis was then conducted using non-metric multidimensional scaling and permutational multivariate analysis of variance (PERMANOVA) analyses. Specifically, we analyzed tree species persistence, changes in tree basal area, changes in the abundance of tree stems, and changes in the the distribution of basal area and stems within 16 tree species targeted for management and throughout the forest community as a whole following management action. Burning and thinning both had significant effects on tree species persistence, basal area, and stem abundance. The interaction of the two management techniques was rarely significant, but since thinning and burning affected different species of trees, the two management practices were complementary. At a whole community level, management by both burning and thinning shifted the forest composition back toward an oak/hickory-dominated forest, and without such management the shift to a maple/birch-dominated forest is likely to continue.