Oak decline is a process induced by the complex interactions of predisposing factors, inciting factors, and contributing factors operating at tree, stand, and landscape scales. It has greatly altered species composition and stand structure in affected areas. Thinning, clearcutting and group selection have been widely adopted as methods of forest harvesting for reducing vulnerability of forests to oak decline by removing susceptible species and declining trees to change species composition and stand structure. Prior research has examined the effects of forest harvesting on oak decline at stand scales over relatively short time frames (e.g. less than 20 years). These stand-scale studies provide a scientific basis for applying stand-scale silvicultural treatments to mitigate oak decline. However, the long-term, landscape-scale effects of these methods are not well studied due to the limited availability of experimental data. In this study, we used a forest landscape model in combination with field studies to evaluate the potential effects of three harvest methods on reducing oak decline at the landscape scale.
Results/Conclusions
Results indicated forest harvesting can be effective in mitigating oak decline but the effectiveness varied among the three harvest methods. Group selection was the most effective methods for the short-term (20 years). Conversely, clearcutting was the most effective methods for the mid-term (50 years). No significant differences were found for the long-run (100 years) among the three harvest methods. The spatial patterns of high risk sites under three harvesting methods were similarly scattered across the landscape at the landscape scale. This scattered pattern was associated with the dissected topography and the scattered distribution of red oaks. However, at a finer scale, there were smaller harvesting patches under thinning alternative. As expected, more basal area and biomass were harvested under the alternative with clearcutting, followed by group selection and thinning. The thinning alternative accumulated the most standing biomass over time, followed by group selection and clearcutting. For balancing treatment effects and retained live biomass, we found group selection to be the most viable alternative for managing oak decline. Insights provided by this study may be useful in developing effective and informed harvesting plans for managing areas impacted by oak decline.