Predicting Lichen-based Critical Loads for Nitrogen Deposition in Temperate Forests

摘要

Critical loads (CLs) define the quantitative exposure to one or more pollutants below which significant harmful effects on sensitive elements of the environment do not occur, according to present knowledge. Management according to CLs generated for epiphytic lichens, a highly nitrogen (N)-sensitive indicator, should protect forested ecosystems from N deposition effects. We tested the hypothesis that epiphytic lichen community composition, specifically the relative contribution of oligotrophs vs. eutrophs to species richness, can be predicted from mean annual precipitation and N deposition. We applied a multiple linear regression model developed for the North American Marine West Coast Forests to dry, mesic, and wet deciduous forests in California and Scotland. Replication of previously published CLs using this model validated our hypothesis, implying that lichen-based CLs for N can be estimated for other temperate forests where natural lichen community composition and mean annual precipitation are known.