Combined field and laboratory investigations of two urban-adapted mosses, Bryum capillare and Bryum argenteum: Incidence of occurrence, microbial associates, rates of growth and development including tolerances to pH, acid rain, and salt

The mosses Bryum capillare and Bryum argenteum have worldwide distribution and are ubiquitous to cities where they are commonly found growing in sidewalk cracks. In Washington, D.C., B. capillare appears to have a higher incidence of occurrence than B. argenteum. A combination of field and laboratory investigations was conducted to determine if this is the case and, if so, what the basis for the differential occurrences of these two moss taxa might be. Sidewalk transacts revealed that colonies of B. capillare were more common than those of B. argenteum at a 4:1 ratio (p<0.05). Both mosses were most frequently present on the south sides of city blocks and least frequently encountered on the north side. Many more microbial associates, such as algae cyanobacteria were detected in B. capillare colonies than in those of B. argenteum. Laboratory studies demonstrated that B. capillare has more rapid rates of growth and development than B. argenteum and that of the two, B. capillare has a broader tolerance to pH, acid rain, and salt, which were all highly significant (p<0.05). From these findings it appears that B. capillare is better adapted to the urban environment. Discussion and implications of the research are presented, along with possible avenues for further research.