Bark Factors Affecting the Distribution of Corticolous Bryophytic Communities

The intensive study of the composition and ecology of bryophytic communities has been markedly lacking in America compared to the great amount of bryocoenological research which has been carried on by Europeans. This lack, perhaps, may be explained by the fact that we do not yet know much about the structure and environment of the larger forest communities which, as a result, occupy the greater part of the American ecologist's time and interest. However, the forest community is found almost always to be a phytocoenosis composed of two or more synusiae. It is not possible to understand truly the phytocoenosis as a whole unless each synusia has been thoroughly studied. It is impossible to isolate any synusia from its phytocoenosis and to treat it as a separate association (Gleason, 1936). On the other hand, each synusia, no matter how small or obscure, has some effect on the development and structure of the whole phytocoenosis and, therefore, intensive studies of the several synusiae are the foundation-stones in any research which would truly portray the life and composition of a complex forest community. In the virgin hardwood forests of the Great Smoky Mountains of eastern Tennessee, the bryophytic synusia not only occurs on rocks, rotting logs, and occasionally soil, but also extends some distance up the trunks of the large trees. The bryophyte layer in all of these types of habitats is made up of readily discernable communities or "unions" (Sirgo, 1935) dominated by one or two species. The present paper is confined to a study of only those bryophytic unions on the trunks of living trees. It is an attempt to learn the effect of various bark factors on the distribution of these unions on the trunks of several species of trees of the dominant synusia. Definite knowledge of the ecology of these bryophytic micro-communities should lead to a better understanding of this synusia and its place in the virgin forest phytocoenosis.