No abstract

Orographic precipitation over interior mountains has resulted in the formation of the inland temperate rainforest, where certain stands are potentially antique and support a rich flora of epiphytic macrolichens. We documented macrolichen diversity across three age-classes in forests of the Interior Cedar-Hemlock biogeoclimatic zone (i.e., ICHwk3 subzone) east of Prince George, British Columbia. Our objectives were to report changes in lichen communities with stand age, identify potential indicators of antiquity, and investigate the functional role of dominant species in the ecosystem. We identified 41 taxa, including 4 alectorioid lichens, 21 foliose chlorolichens, and 16 old-growthassociated chlorolichens and cyanolichens. Older forests supported more species than young or mature forests. The abundance of Lobaria pulmonaria (L.) Hoffm. was strongly correlated with this increase in diversity and may therefore be an appropriate indicator of stand age in the ICH. The increase in L. pulmonaria and other N 2 -fixing cyanolichens with stand age may have significant implications for forest nitrogen budgets in the interior of British Columbia, where atmospheric nitrogen deposition is relatively low and biological N 2 fixation accounts for nearly all of the nitrogen lost to forest harvesting. We hope that this greater understanding of lichen ecology across age-classes will promote sustainable stewardship of the remaining old-growth forests of inland British Columbia.Résumé : La précipitation orographique sur les montagnes de l'intérieur a conduit à la forêt ombrophile continentale, où certains peuplements sont potentiellement anciens et supportent une riche flore de macrolichens épiphytes. Les auteurs ont étudié la diversité des macrolichens, selon trois classes d'âge, dans ces forêts continentales à cèdre et pruche (c.-à-d., zone biogéoclimatique ICHwk3), à l'est de Prince George, en Colombie-Brittanique. Les objectifs étaient de faire état des changements survenant dans les communautés de lichens selon l'âge du peuplement, d'identifier des indicateurs potentiels d'ancienneté et d'étudier le rôle fonctionnel des espèces dominantes dans l'écosystème. On a ainsi identifié 41 taxons, incluant 4 lichens alectoriaux, 21 chlorolichens foliacés et 16 chlorolichens et cyanolichens associés aux vieilles forêts. Les forêts plus vieilles supportent plus d'espèces que les forêts jeunes ou matures. L'abondance du Lobaria pulmonaria (L.) Hoffm. montre une forte corrélation avec l'augmentation de la diversité et pourrait consé-quemment constituer un bon indicateur de l'âge des peuplements d'ICH. L'augmentation du L. pulmonaria et autres cyanolichens fixateurs de l'azote, selon l'âge du peuplement, pourrait avoir des implications significatives quant au budget de l'azote en Colombie-Brittanique continentale, où la déposition atmosphérique de l'azote est relativement faible et où la fixation biologique de l'azote constitue presque la moitié de tout l'azote perdu par la récolte forestière. Les auteurs souhaitent que cette compréhension a...

Epiphytic lichens are highly abundant in many sub-boreal forests and may be important components of nutrient cycling. Decomposition of, and nutrient release from, two cyanolichens (with N2-fixing cyanobacterial partners) and two chlorolichens (with green-algal partners) were quantified to estimate N inputs from epiphytic lichen litter in late-seral forests. Initial decay rates were strongly correlated with initial %N; the high-N cyanolichen litters ( Nephroma helveticum Ach. and Lobaria pulmonaria (L.) Hoffm.) lost 26% more mass than the lower-N chlorolichen litters ( Alectoria sarmentosa (Ach.) Ach. and Platismatia glauca (L.) W.L. Culb. & C.F. Culb.) over the first 4 months. Morphological characteristics also influenced decay, as decomposition of the hair chlorolichen (A. sarmentosa) was similar to that of the foliose cyanolichens, despite an N concentration that was 87% lower. N was immediately released from cyanolichen litters and retained in chlorolichen litters. After 24 months of decay, N concentrations remained highly divergent with 22–27 and 7–8 mg N·g–1 in cyanolichen and chlorolichen litter, respectively. Cyanolichen litter represents 0.1%–2.3% of the total aboveground litter biomass and 0.5%–11.5% of the total N input from aboveground litterfall. Decomposition of cyanolichen litter is estimated to release up to 2.1 kg N·ha–1·year–1 of newly fixed N that would otherwise be unavailable in mature sub-boreal forests.

Hair lichen communities in Engelmann spruce (Picea engelmannii) – subalpine fir (Abies lasiocarpa) forests of the northern Cariboo Mountains (British Columbia) show distinct vertical zonation. Alectoria sarmentosa reaches peak abundance in the lower canopy (over 35 kg/ha) whereas Bryoria spp. lichens reach peak abundance in the upper canopy (over 250 kg/ha). These distribution patterns are accentuated by stand structure with trees growing in clumps retaining significantly higher lichen loading on a per branch basis compared to solitary trees. The vertical zonation of lichen communities is accompanied by distinct trends in canopy microclimate. Snowmelt events account for the largest proportion of observed thallus hydration in both Alectoria and Bryoria. Although canopy microclimate is surprisingly isothermal during rainfall events, the attenuation of thallus hydration after wetting is typically greater for lower canopy exposures. An important exception to this pattern is seen under midwinter conditions, when solar insolation is insufficient to sustain prolonged lower canopy snowmelt. Our data support the hypothesis that ventilation in upper canopy exposures is a contributing factor in the vertical zonation of Alectoria and Bryoria communities. Upper canopy Bryoria rely more heavily on snowmelt events to sustain thallus hydration, whereas lower canopy Alectoria utilize summer rainfall events to a greater extent. We hypothesize that physiological mechanisms, through which these patterns of canopy microclimate influence lichen zonation, may include an intolerance to prolonged wetting by Bryoria and higher resaturation respiration costs in Alectoria, which would limit it to more mesic canopy exposures. We believe that the observed distribution of canopy lichens ultimately reflects the long-term interaction of both physiological and successional processes (lichen colonization and dispersal) within the canopy.Key words: canopy, epiphytes, lichens, microclimate.