Macrolichen and bryophyte responses to coarse woody debris characteristics in sub-boreal spruce forest

Abstract

Coarse woody debris (CWD) forms an important and specific habitat for many species of lichens, liverworts and mosses. We studied the relationships of 88 macrolichen and bryophyte species to CWD characteristics in mature mesic sub-boreal spruce forests in north central British Columbia. CWD characteristics and macrolichen and bryophyte species richness and abundance data were collected. Ordination, regression tree analysis and indicator species analysis were used to establish relationships between selected CWD variables and macrolichen and bryophyte species assemblages, overall species richness and individual species presence and abundance. Decay class and height from ground were the two CWD characteristics that most influenced macrolichen and bryophyte communities. Species composition varied along a continuum of assemblages from a dominance of arboreal lichens on decay class 1 (less decayed) CWD, to Cladonia, Dicranum and Brachythecium species and a diversity of liverworts on decay class 3, to feathermosses and Plagiomnium and Peltigera species on decay class 4 (more decayed) CWD. The height from ground of a log influenced the growth of liverwort and moss species with restricted growth on logs over about 10 cm above the ground. Log species, bark cover and diameter showed more limited influence on community composition in this study. Species were not greatly influenced by aspect (northern versus southern log aspect); however, macrolichen and moss species were more common on the upper sides of logs and several liverwort species were restricted to the lower sides of CWD (upper versus lower sides of logs). These results provide insight into the relationships between CWD characteristics and macrolichen and bryophyte communities, provide a basis for examining forest management impacts on lichen and bryophyte composition and highlight the importance of maintaining a diversity of CWD on the landscape.