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Partial cutting and retention of canopy lichen communities in the ICH
Coxson, Darwyn S.
The retention of canopy lichens was examined using direct canopy access methods (tree climbing) after partial-cut harvesting (30% and 70% removal) in old-growth interior cedar-hemlock forests of the Upper Fraser River valley. No significant treatment effects (total lichen loading) by harvesting type (30, 70, or 100% retention) were seen for three of four lichen-sampling groups (cyanolichen, foliose, and Bryoria group lichens). Only in Alectoria group lichens were treatment effects observed. Although cyanolichen loading was not significantly different in retained trees in harvest blocks many thalli, especially near south-facing edges, were discoloured. Differences among treatment units in the abundance of lichen litterfall, controlled for the proportion of the area that remains unlogged, were greater during the first year after logging than the second year. During the first year after logging, Bryoria and Alectoria litterfall both showed the pattern: group retention>group selection>control. These differences are consistent with the expectation of a post-harvest pulse of litterfall in the partially cut units during the first year after logging, especially among the hair lichens Bryoria and Alectoria. These findings suggest that lichen retention in the residual stand of both partial cut treatments was adequate to meet management goals, but also points to the necessity of future monitoring, as other edge effects (e.g.. microclimate changes) influence future lichen growth and mortality, particularly for the important cyanolichen functional group. Darwyn Coxson.
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