Lichen colonization in natural gap disturbances and old growth stands

Lichen colonization was studied in small (1-3 ha) natural gap disturbances embedded in a matrix of old growth cedar-hemlock forest in east central British Columbia, Canada. Lichen biomass, in relation to stand structural attributes, was examined to understand the role of microclimate, substrate quality, and dispersal capability in lichen colonization. Regenerating trees, approximately 100 years old and of similar structure, in the gap disturbance stands and in the old growth matrix were compared for lichen composition, abundance, and distribution. There was no difference in total lichen biomass between regenerating trees in the gap stands and the old growth stands. However, analysis of the individual functional groups (Alectoria, Bryoria, Foliose, and Cyanolichen) revealed distinct differences between the two stand types. The Bryoria functional group was more abundant in the crowns of regenerating trees in the gap disturbance stands and was distributed vertically through a larger proportion of the tree crown. The Cyanolichen functional group occurred more frequently on the regenerating trees in old growth stands. The Alectoria and Foliose functional groups did not differ significantly in biomass or in distribution between the two tree classes. Additional comparisons showed that tree size (amount of available substrate) positively affected lichen loading, while substrate type (foliated or non-foliated substrates) had no effect. Stand-level projections for arboreal lichen biomass indicated that old growth stands had 19% more biomass and contained greater species diversity than gap stands owning to the abundant cyanolichen community.