Decomposition of hair lichens ( Alectoria sarmentosa and Bryoria spp.) under snowpack in montane forest, Cariboo Mountains, British Columbia

Abstract

Montane old-growth forests on the windward slopes of interior mountain ranges in British Columbia support high loadings of arboreal lichens. These lichens represent a major source of readily labile plant material and potentially play an important role in ecosystem nutrient dynamics. Given the role of winter storms in scouring lichens from within the canopy and the extended length of winter snowpack, from November through to May or even early June, in these ecosystems, the decomposition of lichen litterfall should be heavily influenced by placement within the snowpack. We have examined this factor by placing litter bags containing samples of the hair lichens, Alectoria sarmentosa and Bryoria spp., on top of the winter snowpack in the Cariboo Mountains. Samples were set out in early- (8 Nov.) mid- (16 Jan.) and late- (22 Mar.) winter and subsequently retrieved on spring snow-melt (22 May). Lichen samples that were buried in the lower snowpack all winter long (196 days) lost two-thirds of their original mass. In contrast lichens placed on the snowpack in mid- (127 days) or late-winter (61 days) lost only 6–15% of their total mass, far less than would be predicted on the basis of time in snowpack alone. Spot measurements showed that the snowpack environment effectively buffers litter samples from extreme winter conditions. All lichen samples placed within the snowpack showed much higher C/N ratios on removal, indicating rapid leaching of readily soluble cellular constituents in the snowpack environment. These findings indicate that the snowpack environment plays a major role in decomposition processes in these high-elevation forests and reinforces our view that lichens are a readily labile nutrient source within these ecosystems.