Local Variation in Bryophyte and Macro-lichen Cover and Diversity in Montane Forests of Western Canada

Abstract

The patterns of cover and species diversity (richness and composition) of macro-lichens, bryophytes, and vascular plants are described for a Canadian montane forest in an area where the forest is highly valued both for wood production and for the terrestrial lichen that is a vital part of the diet of the endangered woodland caribou (Rangifer tarandus caribou Gmelin). In 180, 6.5 m × 6.5 m plots placed in nine stands within a 375 km2 area, we found lichens were abundant, but the ground layer was dominated by feather moss. Mean species richness at the plot level for lichens (23) is about double that of bryophytes (13) and vascular plants (11). Differences in species composition are small with any two plots having in common at least 50% of their vascular plants, 60% of their bryophytes, and 70% of their lichens. Comparisons of 10% of the most open with 10% of the most dense canopy plots revealed that the more open sites have greater lichen cover, higher elevation, older trees, more lichen and vascular plant species, less moderately decayed logs, and lower cover of Pleurozium schreberi, the dominant feather moss. Twenty-two species (14%) were found only once; of these five were lichens (9% of the lichen flora), six bryophytes (17% of the bryophyte flora), and 11 vascular plants (17% of the vascular plant flora). None of these is provincially endangered, but all are rare in this particular forest type. Only three of these species occur in the 20% of sites having the most open or dense canopies. Our data indicate that at the local scale, the ground layers of these forests are highly variable and have little local distinctiveness. The lack of strong environmental correlations with species patterns suggests that within the natural forest regime other factors are at least partially responsible for ground layer patterns at the local scale. These may include dispersal and establishment success as well as stochastic disturbance regimes.