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Pennsylvania Regeneration Study Assesses Overstory and Understory Tree Species Communities

Photo of Ecoregions of Pennsylvania color-coded by the levels of similarity found between overstory and understory tree species composition in the Pennsylvania Regeneration Study data of 2001-2005. Todd Ristau, USDA Forest ServiceEcoregions of Pennsylvania color-coded by the levels of similarity found between overstory and understory tree species composition in the Pennsylvania Regeneration Study data of 2001-2005. Todd Ristau, USDA Forest ServiceSnapshot : In 2001, the Commonwealth of Pennsylvania and Forest Service's Forest Inventory & Analysis (FIA) program launched the "Pennsylvania Regeneration Study" to gain a better understanding of understory conditions across Pennsylvania. The landscape-level study was incorporated into a subset of the existing FIA sample locations. At each selected plot, composition and abundance of established tree seedlings and associated non-tree vegetation were recorded. Forest Service scientists analyzed the 2001 to 2005 data to determine whether overstory and understory species composition was similar by forest type or ecoregion and to test various hypotheses about causes for dissimilarity.

Principal Investigators(s) :
Ristau, ToddHanson, Joshua
Research Location : Pennsylvania
Research Station : Northern Research Station (NRS)
Year : 2014
Highlight ID : 655

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.

Forest Service Partners

External Partners

  • Will McWilliams, NRS
  • Christopher Nowak
  • State University of New York - College of Environmental Science and ForestrySyracuse, NY

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