Wednesday, August 4, 2010 - 1:30 PM

COS 67-1: Disturbance characteristics and community resilience in mixed hardwood oak forests

Yvette L. Dickinson and Eric K. Zenner. Penn State University


Forest management is increasingly focused on managing forests as complex systems, which requires understanding a variety of disturbances and their effects.  Disturbance frequency and severity are known to be important in determining the composition of vegetative communities.  Characteristics of the disturbance itself, such the forest strata targeted, are also likely to be important when predicting responses to various disturbances. 
In this study the effects of five cutting treatments across gradients of disturbance severity and forest strata on forest composition, structure and advanced regeneration are examined. The treatments (patch clearcut, thin from above, thin from below, improvement thinning and initial cut of a shelterwood system) were applied to adjacent two acre blocks in Appalachian hardwood forests at three sites approximately 15 years ago.  Their compostional and structural development over time was compared to each other and a control using multivariate techniques. 

The control plots changed over time, indicating succession is ongoing in these forests with increases in structural diversity.  The patch clearcut treatment resulted in the resetting of succession, a simpler forest structure and the dominance of pioneering species.  The thinning from above resulted in intial changes similar but less extreme than the clearcut, followed by a recovery period.  Their current compositions are relatively similar to pre-treatment, with similar structural features.  The remaining partial cutting treatments resulted in disturbance mediated succession, with increases in structural diversity.  In comparison to the control their succession was accelerated in many of the plots.  The effects of these treatments on the advanced regeneration were more varied; however, there were increases in the amount of both the total and shade tolerant regeneration in the initial shelterwood treatment and increases in shade tolerance regeneration in the thinning from above, reflecting the disturbance mediated succession detected in the overstory.