What factors influence colonization of lichens, liverworts, mosses and vascular plants on snags?

Abstract

The dead standing trees i.e. snags are known as habitat for epiphytic and epixylic species including first of all lichens and bryophytes. The vascular plants are much rarer on this type of coarse woody debris (CWD). The eighty snags (CWD elements higher than 1.5 m) of Norway spruce Picea abies and beech Fagus sylvatica in the Karkonosze Mts. were examined for the presence of lichens, liverworts, mosses and vascular plants. The height of snags, their decomposition stage, cover of bark, diameter at breast height (DBH) as well as site conditions (elevation, slope and aspect, presence in forest community) were measured and noted. The percent cover of plants and lichens were estimated on each snag. Totally 99 taxa were recorded. There lichen species were dominant (44), followed by mosses (34), liverworts (13) and there were only 8 vascular plants. The total species richness varied from 1 to 22 taxa. The species composition growing on snags was subjected to canonical correspondence analysis and statistical analyses. They revealed that the species identity of snag is one of the most important factors influencing species composition. The number of species is positively correlated with DBH whereas decomposition stage, presence of bark, snag height are not significant factors. The species richness increases also with altitude what is connected with higher abundance of spruce snags. The occurrence of snags in this area is mainly associated with forest management practices in the past. Despite of some observed patterns in colonization of snags they are important habitat especially for lichens.