Bryology and Lichenology
Vitt, Dale , Finnegan, Laura , House, Melissa .
The responses of lichens and bryophytes to forest thinning regimes in montane forests of Alberta, Canada.
Pinus contorta-dominated montane forests of western Canada with relatively dense tree canopies have ground layers covered by abundant bryophytes, especially feather mosses (Pleurozium schreberi and Hylocomium splendens), while those with more open canopies are dominated by species of fruticose lichens, especially Cladina mitis and C. rangiferina. Woodland caribou (Rangifer tarandus caribou) are a threatened species and prefer open, Cladina-dominated forests for winter food supply. This study investigated if opening the forest canopy through a series of selective cutting regimes of mature montane forests of the Canadian Rocky Mountain foothills would result in an increase in the abundance of lichens in order to provide a better food supply for woodland caribou. Forests were thinned in 1997 by removing 20, 40, and 60% by volume. Plant and lichen responses were assessed by the establishment of 180 42.25 m2 plots equally placed in each of the thinning treatments, plus control plots in uncut forests. A subset of 97 plots were surveyed in 2016, 19 years after treatment, for vegetative cover and species richness. The survey found that control plots were different from all three canopy cover groups, and the three canopy cover groups were intermixed within NMDS ordination space. The control set of plots were dominated by feather mosses, whereas the canopy cover (treatment) groups were dominated by unoccupied space. In all three canopy cover groups, feather mosses decreased between 31 and 47% compared to the control group, whereas cover of unoccupied space was significantly greater in treatment groups compared to the control group (58-64% vs. 32%). In 2016, control plots had 6% cover of Cladina, 6% other lichens, 32% unoccupied space, and 48% feather mosses. Comparatively, treatment plots had 8% cover Cladina, 10% other lichens, 61% duff, and 11% feather mosses. Overall between 1997 and 2016, lichen cover increased 6%, feather mosses, as expected have decreased markedly, and unoccupied space was double that of the controls. Despite these changes in abundance, species richness (gamma) largely remained the same for vascular plants, lichens, and bryophytes. We conclude that bryophytes have not recovered after harvest, Cladina and other lichens have had a modest increase in cover, but after 19 years there remains large unoccupied areas of ground. Harvesting had little or no effect on species richness of either bryophytes or lichens.
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1 - Southern Illinois University, Department of Plant Biology, Carbondale, IL, 62901, usa
2 - fRI Reaearch, 1176 Switzer Drive, Hinton, AB, T7V 1V3, Canada
Presentation Type: Oral Paper
Candidate for Awards:None