USDA Forest Service

Forest Inventory and Analysis National Program


Forest Inventory & Analysis
National Office
U.S. Forest Service
1400 Independence Ave., SW
Washington, D.C. 20250-0003

(703) 605-4177

United States Department of Agriculture Forest Service.

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Program Features


Forest Health Indicators


Ozone Crown Condition Soil Quality Lichen
Down Woody Materials Vegetation Tree Mortality Tree Growth


Lichen Indicator


Lichens are fungi that live in intimate association with algae. Lichens are very responsive to environmental stressors in forests, including changes in forest structure, air quality, and climate. In Forest Inventory and Analysis (FIA), we collect data on epiphytic lichens, those species growing on trees and shrubs.


Why is the Lichen Indicator Important?

A lichen community is a group of various species of lichens present at a site. The composition of an epiphytic lichen community is one of the best biological indicators of nitrogen and sulfur-based air pollution in forests. Their sensitivity results from their total reliance on atmospheric sources of nutrition. Because lichens are so sensitive to these pollutants, they are useful as an early indicator of improving or deteriorating air quality. Using lichens, we can answer the following questions:

  • Is regional air quality (specifically nitrogen- and sulfur-based pollutants) changing over time? If so, is it improving or deteriorating?

  • In what fraction of an area do lichens indicate the possibility of air pollution impacts on forest productivity and biodiversity?

Since the effects of air pollutants on trees can be difficult to separate from other influences on growth (such as soil variations), epiphytic lichens provide a clear indication of potential air quality impacts on total forest productivity.   

For more information about the Lichen Indicator view the FIA Lichen Indicator Fact Sheet.

USDA Forest Service
Last Modified: January 26, 2005

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