Cryptogams on decaying wood in old-growth forests of southern coastal British Columbia

We studied the floristic composition of lignicolous cryptogams (i.e. bryoph ytes and lichens inhabiting decaying wood) in the old-growth coniferous for ests of southern coastal British Columbia. The composition of the cryptogam s was related to forest communities (described by vegetation units using fo rest floor cryptogams and vascular plants) and regional climates (described by biogeoclimatic zones). The study is based on a total of 247 sample plot s, each of 0.04 ha in size. The plots were located in three different bioge oclimatic zones and were classified into 12 alliances and four orders in a previous study. We used indicator species analysis to determine cryptogam i ndicator species for each vegetation unit and biogeoclimatic zone, and used similarity analysis and multivariate analyses (discriminant analysis and d etrended correspondence analysis) to detect differences in the floristic co mposition of the cryptogams among sample plots, vegetation units, and bioge oclimatic zones. Most of the cryptogams in this study had a narrow distribu tion, and only < 5 % of the species were present across all the vegetation units and biogeoclimatic zones. The overall means of Jaccard coefficients b etween two sample plots from the same vegetation unit (alliance or order) o r biogeoclimatic zone were significantly higher (P < 0.05) than those from different vegetation units or biogeoclimatic zones. The difference in the m ean Jaccard coefficients within- and between-units was highest for zones. T he results of detrended correspondence analysis and discriminant analysis s uggest that the composition of lignicolous cryptogams changes with the chan ge in the floristic composition of forest floor vegetation. When the first axes of detrended correspondence analysis were compared, the Pearson's corr elation coefficients between the first axes of lignicolous cryptogams and f orest floor vascular plants and between the first axes of lignicolous crypt ogams and forest floor cryptogams were 0.78 and 0.87, respectively. The deg ree of correspondence in the composition of lignicolous cryptogams and fore st floor vegetation increased from alliance to order to biogeoclimatic zone . This trend suggests that the floristic composition of lignicolous cryptog ams is influenced at the community level mainly by edaphic conditions and a t the regional level by climatic conditions.