Vertical distribution and nitrogen content of epiphytic macrolichen functional groups in sub-boreal forests of central British Columbia

Abstract

Vertical distribution, biomass abundance and nitrogen stocks of epiphytic macrolichens were examined in the two dominant tree species, interior hybrid spruce (Picea engelmannii Parry ex Engelm. x glauca (Moench) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.), in sub-boreal spruce forest ecosystems of central British Columbia. Lichens were contrasted between two different site types containing either high (High Cyano) or low (Low Cyano) epiphytic cyanolichen abundance. A single rope technique was used for canopy access and a ‘clump’ method was used to estimate the abundance of arboreal lichens at different heights within both canopy tree species for five functional groups: Bryoria spp., Alectoria sarmentosa, foliose chlorolichens, bipartite cyanolichens, and Lobaria pulmonaria (the only tripartite cyanolichen). In this way, the relationship between average lichen biomasses and tree height for each tree species were assessed. We determined that biomass was dependent on tree height and species, with a greater abundance of lichen appearing on fir trees (mean±SD; 1588±428gtree−1) than the generally taller spruce trees (917±422gtree−1). Foliose chlorolichen biomass was more abundant in trees with low abundance of L. pulmonaria (777.1±365.9gtree−1) than those with a high abundance of L. pulmonaria (553.6±400gtree−1). Much of this increase in chlorolichen biomass in trees with low cyanolichen abundance was a result of greater chlorolichen abundances in lower canopy positions where cyanolichens would otherwise predominate. Although bipartite cyanolichens had a higher %N (∼3.2%N) than L. pulmonaria (2.3%N) of dry mass, there was a much higher abundance of L. pulmonaria in the canopy of High Cyano sites containing a larger amount of N (4.04±0.95kgNha−1) than in all bipartite cyanolichens combined (2.33±1.11kgNha−1) or any other lichen spp. Chlorolichens are poor competitors for lower branch positions when cyanolichens such as L. pulmonaria are abundant, the latter of potential importance for N inputs into N-limited sub-boreal forests of central BC.