The importance of epiphytic lichens in mineral cycling

Mineral capital in epiphytic lichens varies considerably fromforest to forest depending primarily on the biomass of lichens present and canbe at least as high as 27 kg ha" for N, 3.6 kg ha' for P, 9 kg ha " for K, 9.4kg ha" for Ca and 1.7 kg ha-' for Mg. For three ecosystems, comparingDouglas fir, balsam fir and oak woodland, lichens seldom accounted formore than 10% of the annual, above-ground turnover of a mineral. Lichenswere relatively more important in the cycling of N than of P and K and ofleast importance in the cycling of Ca and Mg. Quantities of minerals leachedfrom lichens appear to be small compared to quantities released through bio-mass turnover. Lichens may influence entry of minerals into ecosystemsthrough nitrogen fixation and interception of aerosols. Although atmosphericinputs may be sufficient to meet N, Ca and Mg requirements of epiphyticlichens, P and K appear to be obtained primarily as leachates from othercanopy components. Minerals that have been taken up by lichens may sub-sequently reach the surrounding plant or animal communities via litterfall,leaching, bacterial incorporation or non-cellular particle formation.