Forest Inventory and Analysis National Program

Program Features

Forest Health Indicators

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.

Click here to go to the Lichen Indicator website.