Bryophytes and Lichens of North America: Diversity, Function and Importance
Haeussler, Sybille , Williston, Patrick , Cichowski, Debbie .
Changing lichen and bryophyte abundance in dry pine ecosystems of west-central British Columbia.
Open pine forests with understories dominated by Cladina, Cladonia and Stereocaulon lichens are a conspicuous feature of northern forests. In west-central British Columbia, we consider these slow-growing but functionally important ecosystems as bellwethers of global change. Our hypothesis was that recent changes in disturbance regimes and resource availability are precipitating state shifts from lichen-dominated to bryophyte- and vascular plant-dominated understories with implications for regional biodiversity. In Pinus contorta–Cladina-Pleurozium ecosystems of the Central Interior Plateau we used permanent photoplots and transplant experiments to monitor changes in lichen, feathermoss and vascular plant coverage over seven years following a massive mountain pine beetle outbreak. Five-year results showed a 41 % decrease in terricolous lichen abundance in beetle-killed stands with corresponding increases in Arctostaphylos uva-ursi, feathermosses, and other plants. At 7 yr, conditions appear to be stabilizing and lichen cover is stable or increasing on nearby clearcuts. In subalpine Pinus albicaulis–Cladina-Dicranum ecosystems on the leeward slopes of the Coast Mountain Range, we returned after 22-29 yr to reinventory 4 sites affected by cumulative white pine blister rust and mountain pine beetle mortality. Lichen cover declined on 2 submesic sites, but nearly doubled on 2 xeric sites. Our results suggest that lichen-bryophyte dynamics are more complex than initially hypothesized.On resource-poor sites where terricolous lichens face limited competition from other vegetation, death of overstory pine may increase lichen abundance, whereas on more mesic sites, declines in lichen are observed. All-in-all, the sky appears to be falling less rapidly than hypothesized. Feedbacks and thresholds will, hopefully, help to maintain lichen-dominated ecosystems in the landscape, even as climatic conditions become less favorable.
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1 - Bulkley Valley Centre for Natural Resources Research & Management, Smithers, BC, Canada
2 - Gentian Botanical Research, Smithers, British Columbia, Canada
3 - Caribou Ecological Consulting, Smithers, British Columbia, Canada
Presentation Type: Symposium or Colloquium Presentation
Date: Tuesday, July 29th, 2008
Time: 3:30 PM