Lichen indices assess local climate and air quality status in the Mid-Atlantic Region, U.S.A.

Abstract

Lichen-based indices were developed for monitoring local climate and air quality impacts in the United States of America (U.S.A.) Mid-Atlantic states (MidA). The U.S.A. Forest Service Forest Inventory and Analysis Program (FIA) uses such biological indicators to monitor forest environments. Index development used a unique combination of recommended analysis techniques. The Climate Index (Axis 1 of nonmetric multidimensional scaling [NMS] ordination of 189 plots, 80 lichen species) accounted for 44.7% of data variation, and was correlated with latitude, temperature and humidity (r2 = 0.5 to 0.7). The Pollution Index was based on abundances of 10 tolerant and 27 sensitive lichen species selected from Indicator Species Analysis and other techniques (210 plots, 180 species). Strong quantitative support guided careful selection of pollution indicator species. The Pollution Index was strongly correlated with Al, Cu, Fe, N and S measured in lichen samples (51 plots; maximum r2=0.796), and with 51-plot NMS Axis 1 (r2=0.694; 41.7% of information) correlated with pollution. Indices were uncorrelated with each other or with nearby forest cover, another important factor. From within-site repeatability, Climate Index changes of 13–21% of full range and Pollution Index changes of 18–24% will be detectable. These indices fill a gap to complete FIA index coverage for much of eastern U.S.A. Both indices are suitable for application in other MidA studies. Comparisons with similar FIA studies supported guidelines for use of our indicator selection process and evaluation of environmental interactions to improve other studies.