| Summary: | This thesis had two general objectives: to describe the patterns of distribution and
abundance of terrestrial bryophytes in old growth subalpine forests at two study areas
(Cypress and Mt. Seymour Provincial Parks) in southern coastal British Columbia, and to
determine the scale at which environmental factors influence these patterns.
Using principal components analyses, it was demonstrated that regional scale
("biogeographical") plant associations correspond only weakly to the patterns of distribution
and abundance of terrestrial bryophytes. Thus, bryophytes may "sense" the environment
differently than is the case with vascular plants, i.e. their distribution may be more related to
microclimate characteristics.
Patterns of bryophyte diversity and abundance were examined at the scale of 20m x
20m study plots using canonical correlation analysis and Pearson correlation coefficients. At
this scale, bryophyte diversity and coverage were found to be positively correlated with
variables relating to increased light availability. Plots with a northern aspect, reduced canopy
coverage, more abundant vascular vegetation, lower abundance of woody debris, and lower
LFH depth and organic matter content were associated with higher bryophyte diversity and
abundance.
The microscale (i.e. 0.1m² microplots) environmental preferences of individual
bryophyte species were examined using Pearson correlation coefficients, and by examining
the range of microhabitat conditions in which species were noted to occur. Species in open
habitats exhibited narrower ranges of soil surface layer (LFH) characteristics (pH, C:N
ratios) than those in closed habitats, possibly because of greater flux in soil surface
conditions (e.g. litterfall) in closed sites.
The substratum affinities of bryophytes were examined using their microscale
frequencies on available substrata. To investigate the combined influence of substratum and
microhabitat, the species associations on different substratum types were investigated using
principal components analysis. Microscale features (environment and/or substratum) were
found to be closely related to the distributions of some bryophyte species. Assemblages on
fine litter and woody debris in open, "stable" habitats with abundant bryophytes and vascular
plants differed from those in closed-canopy, steeper, "unstable" habitats with lower
bryophyte and vegetation cover. Bryophyte assemblages occurring on exposed humus and
creeping stems were most closely related to the availability of the substratum types.
The relationship of bryophyte species to stable and dynamic types of
microenvironments was investigated using logistic regression. Bryophytes associated with
unstable environments (i.e. dynamic surface layer) had a more random distribution than
species that were associated with open, stable habitats, or that displayed strong substratum
affinities. The physiological tolerance of species for microhabitat features (environment
and/or substratum), and the degree of microhabitat stability seem to play important roles in
determining the structure and dynamics of terrestrial bryophyte vegetation. === Science, Faculty of === Botany, Department of === Graduate
|
|---|
