Site factors determining epiphytic lichen distribution in a dieback-affected spruce-fir forest on Whiteface Mountain, New York: stemflow chemistry

Abstract

Epiphytic lichen diversity in a dieback-affected forest of red spruce (Picea rubens Sarg.) and balsam fir (Abies balsamea (L.) Mill.) on Whiteface Mountain, New York, U.S.A., was higher on dead compared with living trees and on fir compared with spruce. Diversity differed more between living and dead spruce than between living and dead fir. Cover of all lichen species that occurred on more than 50% of the sample trees, except for two species, decreased with increasing mean concentration of NO3–in stemflow. Concentrations of NO3–were higher on living spruce compared with dead spruce and with living and dead fir. The negative correlations between lichen cover and NO3–concentration may reflect either a decrease of lichen abundance caused by toxic effects of higher NO3–concentrations or a removal of NO3–from stemflow by epiphytic lichens. Experimental exposure of Hypogymnia physodes to NaNO3reduced chlorophyll concentrations. This result, together with estimations of lichen and needle biomass, indicates that a dependence of lichen cover on NO3–concentrations in stemflow may be the cause for the negative correlations. The sulphur concentration in stemflow did not affect lichen abundance on Whiteface Mountain. The manganese concentration in stemflow may have an effect on single species.Key words: forest dieback, manganese, nitrate assimilation, nitrate toxicity, precipitation chemistry, sulphur.