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Northern Research Station
11 Campus Blvd., Suite 200
Newtown Square, PA 19073
(610) 557-4017
(610) 557-4132 TTY/TDD

Research Topics

  [photo] showing vegetation.


The Vegetation Indicator is a set of variables collected on Phase 3 (forest health) FIA plots. It is designed to inventory vascular plants in our forest ecosystems that are not sampled during the FIA Phase 2 inventory. Other data collected include vegetation community vertical structure, ground cover components, and non-forest land-uses falling within the plot. 


Why is the diversity and structure of vegetation important?

Vegetation is the source of primary production and a fundamental determinant of habitat and wildfire fuel profile characterization.  As such, changes in vegetation can have cascading effects throughout an ecosystem. While individual species can be important indicators of a site’s potential productivity, economic value, and wildlife forage and shelter, changes in the composition and spatial arrangement of vascular plants in a forest may indicate the presence of:

  • Chronic stresses such as discrete site degradation
  • Climate change
  • Pollution 

These stresses can lead to decline or local eradication of sensitive species, as well as increase and dominance of opportunistic species, such as many weedy non-native plants. 

Changes in species diversity, structural diversity, and the abundance of nonnative species are common national concerns, as reflected in the international criteria for assessing sustainability of forestry practices. The Forest Inventory and Analysis (FIA) Vegetation Diversity and Structure (VEG) Indicator provides:

  • Baseline data to assess trends in overall forest structure
  • Vascular plant species richness
  • Relative abundance, spatial distribution, and frequency

The vascular plant species inventory is conducted with consistent methods across the vast array of forest types in the nation. Data collected allows analysts to compare the relative species diversity and distribution of individual species across broad geographic regions. 

Data from the Vegetation Indicator can be used by many people covering a broad range of interests, including:

  • Distribution patterns of any species of interest (invasive, noxious)
  • Functional group (nitrogen fixers, wildfire accelerants or inhibitors)
  • Life form and/or understory structure as it pertains to wildlife habitat
  • Fuel profiles
  • Disturbance histories

For more information about the Vegetation Indicator view the FIA Vegetation Indicator Fact Sheet. (pdf 451K)



Last Modified: 03/12/2008