Variation in epiphytic lichen and bryophyte composition and diversity along a gradient of productivity in Populus tremuloides stands of northeastern British Columbia, Canada

• Published in: Écoscience (Sainte-Foy) 2008-03, Vol.15 (1), p.101-112
• Main Authors: Boudreault, Catherine, Coxson, Darwyn S., Vincent, Elise, Bergeron, Yves, Marsh, Janet
• Format: Article
• Language: English
• Subjects: aspen; Autres s / Other s; Bark; Bryophytes; Chemical bases; Epiphytes; Forest canopy; forest productivity; Forest stands; indice de qualité de station; Lichens; peuplier faux-tremble; productivité forestière; site index; Tree age; Tree trunks; Trees
• ISSN: 1195-6860; 2376-7626
• DOI: 10.2980/1195-6860%282008%2915%5B101%3AVIELAB%5D2.0.CO%3B2

The influence of site productivity on epiphyte diversity on aspen (Populus tremuloides) trunks was examined in 19 stands from northeastern British Columbia, whose site indices (dominant tree height at 50 y) ranged from 6.7 to 27.9 m. Canopy epiphyte communities responded strongly to gradients in site productivity. Correlations between plot scores along the axes of non-metric multidimensional scaling ordinations and environmental variables indicated that site index, diameter at breast height, tree age, bark cation concentrations (K, Ca, Mg, and Mn), canopy cover, and bark roughness were significant explanatory variables for epiphyte community composition at trunk base and at breast height. Less productive sites (site indices below 17.25) were dominated by crustose lichens. Indicator species in these sites included Caloplaca cerina, C. holocarpa, and Catillaria glauconigrans. Closed-canopy environments in the more productive stands were dominated by mosses. Associated indicator species included Brachythecium spp., Pylaisiella polyantha, and Eurhynchium pulchellum. Cover of epiphytic species at breast height was higher in stands with low site indices, whereas cover of epiphytic species at trunk base was higher in stands with high site indices. These findings would suggest that management for epiphyte community diversity in aspen dominated landscapes will necessitate the retention of mature aspen stands from across a range of site productivities. L'influence de la productivité du site sur la diversité des épiphytes sur les troncs de peupliers faux-trembles (Populus tremuloides) a été examinée dans 19 peuplements forestiers du nord-est de la Colombie-Britannique ayant des indices de qualité de station entre 6,7 et 27,9 m (hauteur dominante à 50 ans). Les communautés épiphytes de la canopée répondaient fortement aux gradients de productivité du site. Des corrélations entre la position des parcelles sur les axes d'ordination axes d'ordination de cadrage multidimensionnel non-métrique et les variables environnementales indiquaient que l'indice de qualité de station, le diamètre à hauteur de poitrine, l'âge de l'arbre, les concentrations de cations dans Pecoree (K, Ca, Mg et Mn), le couvert forestier et la rugosité de l'écorce étaient des variables explicatives significatives de la composition des communautés d'épiphytes à la base des troncs et à hauteur de poitrine. Les sites moins productifs (avec des indices de moins de 17,25) étaient dominés par des lichens cru