MILLS, SUZANNE ELIZABETH*, S. ELLEN MACDONALD, AND DALE H. VITT. Department of Renewable Resources, University of Alberta, Edmonton, Alberta, 2E9 T6G. - Patterns of bryophyte species diversity at three scales in conifer dominated boreal forest stands.
The maintenance of species diversity is becoming a key component of
sustainable forest management. In the boreal mixedwood of northern
Alberta, conifer dominated stands over one hundred years old are among
those most threatened under present harvesting regimes. These stands
are also important habitat for many bryophyte species. Wise
management requires an understanding of the mechanisms controlling
bryophyte species richness and evenness in order to either facilitate
the identification of species rich areas or to improve the bryophyte
habitat in managed stands. This study examines the relationship
between microclimate and substrate availability, and bryophyte species
richness and evenness at different scales. I sampled bryophyte
species occurrence and abundance at three scales: the stand (10 ha),
the mesosite (25 X 25 m plots to capture within stand variation), and
the microsite (structural elements of the boreal forest providing
unique substrates for moss colonization). Percent full sun, PPFD
(Photosynthetic Photon Flux Density), soil moisture and pH, vascular
plant species richness, microtopography and area of available
substrate were measured to estimate inter-mesosite variability.
Microsite variability was estimated using a relative measure of mean
exponential temperature in combination with descriptive classes of
substrate quality. Sampled microsites consisted of 74 stumps, 88
logs, 90 trees, 90 patches of undisturbed soil and 33 patches of
disturbed soil. Light and temperature were more variable within
stands than between stands (57% and 19 % of the variation
respectively), while soil moisture and pH were more variable at the
stand level (72% and 30% of the variation respectively). The stand
with the greatest species richness had the greatest vascular plant
species richness, as well as the highest soil moisture and pH.
Bryophyte species richness and evenness is related to variability in
forest structure and environment both within and between stands.
Key words: boreal, bryophytes, Canada, diversity, management, moss