Plant diversity in wooded moderate-rich fens across boreal western Canada: an ecoregional perspective

Abstract

Ecoregions are increasingly being used as a framework for conservation planning. The Mid-Boreal Uplands Ecoregion stretches across Canada from Manitoba to British Columbia. From the perspective of conservation and to understand the dynamics of plant diversity and community composition in a common wetland type, we examined the plant communities and environmental variables in 80 wooded moderate-rich fens within this ecoregion. Regional diversity totalled 273 species, with 86 bryophytes and 187 vascular plants. Total diversity was greatest in Manitoba and decreased in a longitudinal trend west through Saskatchewan and Alberta. This may be related, in part, to orographic precipitation at Manitoba sites and a gradient of growing degree days. Richness of locally rare vascular plants exhibited a clear west to east gradient. Ten species of provincially rare vascular plants were observed across the ecoregion, but without pattern. Ordinations and other analyses revealed distinct plant communities for all three locations, with vascular plant assemblages more discrete than bryophyte assemblages. Bryophyte diversity increased with latitude and longitude, whereas vascular plant diversity decreased. Additionally, elevation, precipitation, surface water alkalinity, water temperature, percent overstory density, and peat organic C played a role in determining species richness and community composition. Overall, species composition and diversity in a single wetland type exhibited continuous change across multiple political jurisdictions at the ecoregion scale. Conservation plans for wetlands at the ecodistrict scale may be preferable.