Patterns of bryophyte diversity in the interior and coastal cedar -hemlock forests of British Columbia.

摘要

In Canadian cedar hemlock forest, floristic habitat sampling (FHS) methodology recorded more than twice as many bryophyte species as traditional plot sampling (PS). FHS samples a mosaic of mesohabitats (i.e., forest, streams, seeps, and cliffs) that are often not sampled in traditional plot studies, resulting in under estimates of species richness, including many rare species, and a full understanding of the patterning of diversity.;At the regional scale (i.e., provincial), climate and large-scale catastrophic disturbance (i.e., fire and logging) are the most important environmental variables influencing bryophyte vegetation patterns in the cedar hemlock landscape of British Columbia (B.C.). Species composition in coastal western hemlock (CWH) stands differ from those in the interior cedar hemlock zone (ICH). In general, the CWH has a higher abundance of bryophytes, particularly hepatics than the ICH. Floristic affinities are associated with bryophyte vegetation in the CWH and ICH. Temperate species, especially western North American endemics, are almost exclusive to the CWH. Boreal species are more common in the ICH.;At the stand scale, time since the last large-scale disturbance and habitat heterogeneity strongly influence the patterning of bryophyte diversity in the ICH and CWH. Old-growth cedar-hemlock forests have between 33% (ICH) and 66% (CWH) more species than young forests disturbed by either wildfire or logging. Stands with high mesohabitat quantity (i.e, number of different kinds) had high bryophyte diversity.;At the local scale, bryophyte diversity is largely dependent upon mesohabitat quality and quantity. Within an age class, mesohabitat quality is a function of the number and types of microhabitats. Ecosystem management plans must be aimed towards maintaining the diversification of mesohabitats/microhabitats for the preservation of high bryophyte diversity. Mesohabitat and microhabitat bio-indicators associated with high bryophyte diversity are listed for old growth forests in each biogeoclimatic zone. These bio-indicators can be used to preserve the crucial habitats for rare species, and identify "hot spots" for conservation. Large-scale disturbance such as forestry heavily threatens the sustainability of these highly diverse communities. Bryophyte diversity in the cedar-hemlock forests of British Columbia will be sustained through ecosystem management of old growth legacies (i.e., landscapes, stands and components of these) and the preservation of areas of high diversity.