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UBC Theses and Dissertations

Distribution and abundance of arboreal lichens and their use as forage by blacktailed deer Stevenson, Susan K.


Biomass of arboreal lichens used as winter food by blacktailed deer was studied. Three methods were used to assess abundance of Alectoria sarraentosa and Bryoria spp. Lichen biomass was measured by sampling the lichens from felled trees. A system of visual estimates of lichen abundance was developed and related to biomass estimates obtained by sampling. A predictive equation {Y = 158.03 {A x CL), where Y is lichen biomass, A is an estimate of lichen cover on a portion of the tree crown, and CL is crown length; n = 40; Sy,x = 376,89; r2 = 0,75) was used to extrapolate lichen biomass values from sampled trees to unsampled trees. The value of large-scale colour infrared air photography as a tool for inventorying lichen abundance was assessed, using densitometry and photo interpretation. Some positive relationships with lichen abundance were found using each method, but neither densitometry nor photo interpretation was demonstrated to have strong potential for use in inventorying abundance of arboreal lichens. Biomass of Alectoria (sensu lato) on the 14 plots studied ranged from 21 to 1528 kg/ha. Physical and vegetative characteristics of the plots were measured and related to lichen abundance. Taken together, slope, aspect, and elevation accounted for 82 percent of the variation in lichen abundance. Forest productivity was negatively related to lichen abundance, lithin the range of sites studied, Alectoria (s.1.) was most abundant on moderate to steep south-facing slopes, at elevations above 500 m, where tree growth was poor. To assess availability of lichens and their utilization by deer, litterfall was measured inside and outside exclosures on three sites where levels of deer use in winter were known. The relationships between litter deposition rates and weather were examined. Quantities of Alectoria (s.1.) litter were 69.9 kg/ha/180 days in a severe winter range area, 151.2 kg/ha/180 days in a mild winter range area, and 31.9 kg/ha/180 days in a poor winter range area. On all three sites, significantly more (p ≤ 0.05) Alectoria litter was present inside than outside exclosures; guantities of non-lichen litter did not differ significantly. Utilization of Alectoria was 37, 53, and 52 percent of available guantities on the three sites, respectively. The relationship between lichen abundance and selection of winter habitat by blacktailed deer was assessed, based on pellet group counts, track counts, and the data of other investigators. Areas selected by deer as winter range tended to be moderate or high in lichen abundance.

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