Observations on the ecology of the lichen genus Bryoria in high elevation conifer forests

Abstract

The distributional ecology of the tree-dwelling 'hair lichens' Bryoria fremontii and B. pseudofuscescens is examined, based on observations in high elevation conifer forests of inland British Columbia. Seven obvious microscale and mesoscale patterns are reported for one or both of these species: (1) a failure to successfully colonize branches occurring below the upper limit of the winter snowpack; (2) an occurrence in much lower abundance over the outer, foliated portions of branches than over the inner, defoliated portions of the same branches; (3) a tendency to periodic die-off in the outer, foliated branches, but not in the inner, defoliated branches; (4) a development of disproportionately heavier loadings over old, seriescent trees than over young, vigorously growing trees of similar size; (5) an ability to colonize all levels of the forest canopy, including the upper crowns of trees; (6) an anomalously higher biomass in young stands growing in exposed sites than in young stands growing in sheltered sites; and (7) a development of considerable biomass in poorly illuminated stands that are nevertheless well ventilated. Based on these observations, the main distributional features of these species, and of Bryoria as a whole, are assumed to reflect a pronounced sensitivity to prolonged wetting, especially as a result of snowmelt. Other environmental factors are apparently less important, at least in the study area.