Summary
Future composition and stocking of eastern hardwood forests will depend heavily on tree seedlings and saplings that are in position to replace the existing overstory following disturbance. Forest Service researchers assessed the similarity of current overstory and understory tree species communities on 539 Pennsylvania Regeneration Study sample locations to investigate the resilience of the current species composition of Pennsylvania's forests. The sample locations were distributed across two forest-type groups: mixed oak and northern hardwoods (beech, birch, and maple), and seven ecological sections. Similarity of overstory and understory species composition did not differ by forest-type group, but the degree of similarity observed did differ by ecological section. The Northern Glaciated Allegheny Plateau and Allegheny Mountain sections had the highest levels of tree species similarity, and the Northern Appalachian Piedmont and Western Glaciated Allegheny Plateau sections had the lowest levels. The ecological sections with the lowest levels of similarity, those where future forests will likely differ most from current forests in composition,ninclude areas of Pennsylvania most affected by landscape fragmentation and non-tree vegetation, particularly grass and non-native species. Future research will focus on understanding what this means for the future stability of eastern hardwood forests.
