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Lichens in forest ecosystems
... As a group, canopy lichens have commonly been used as indicators, both for their sensitivity to air pollution and as markers of forest successional stages (Esseen and Coxson 2015). Conditions suitable for the establishment and growth of old-forest dependent oceanic lichen communities typically do not occur for two centuries or more after stand-replacing disturbance events (Campbell and Fredeen 2004;Price et al. 2017). ...
The Kispiox Timber Supply Area, a 1.3 million ha region in northwestern British Columbia, Canada, supports a significant assemblage of temperate rainforest (oceanic) lichens that depend on old forests. Given their known sensitivity to edge effects, we ask whether or not the current configuration of Kispiox Old-Growth Management Area (OGMA) reserves will provide viable future habitat for oceanic lichens as surrounding landscapes are progressively logged in coming decades. Landscape indicators were calculated from provincial map data sets. Old Interior Cedar–Hemlock biogeoclimatic zone forests, the primary habitat for Kispiox oceanic lichens, had a landscape shape index of 6.4 in OGMAs, indicative of elongate shapes susceptible to edge effects. Mean patch size in OGMAs was 43 ha, with the largest patch size being 1 378 ha. In contrast, the landscape shape index for pre-industrial old cedar–hemlock forests was 1.3, with a mean patch size of 1 293 ha and largest patch size of 23 357 ha. When modelled edge effects were extended to 120 m, only 25% of cedar–hemlock forests in Kispiox OGMAs remained interior habitat (7 754 ha total). Adoption of silvicultural practices that maintain buffer zones around existing OGMAs, and the designation of additional OGMAs, especially in watersheds with intact old cedar–hemlock forests, is recommended to conserve oceanic lichen communities in the Kispiox region.
Links between lichen morphology, internal/external water storage and distribution patterns are poorly known. We compared mass- (WC, % H2O) and area-based (WHC, mg H2O cm-2) hydration traits in seven
pendent or shrubby Usnea species from oceanic to continental climates. All species held more external than internal water. Internal WHC and WC increased with specific thallus mass (STM, mg cm�2), while external WC decreased. Shrubby species had higher STM and total WHC than pendent ones. The continental Usnea hirta (shrubby) had the highest total and external storage; the suboceanic Usnea longissima (pendent) had the lowest internal storage. Morphology drives hydration traits and explains distributions of some Usnea species, but such traits did not distinguish oceanic from widespread
species. Shrubby species maximize water storage and thus prolong hydration after rainfall events and/or hydration by dew. The low internal WHC in pendent species is likely an adaptation to frequent hydration
in humid air.
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