Epiphytic lichen biomass in a boreal Norway spruce forest

Abstract

Abstract:Alectorioid and foliose lichens were weighed from full-size branches of Picea abies cut at two canopy heights in 100 trees in an old subalpine forested area in eastern Norway. The mean lichen biomass per branch decreased from 46 to 37 g moving upwards from 2–3 to 5–6 m canopy height. The lichen biomass correlated strongly with branch size variables, branch diameter alone explaining 48 of the variation in lichen biomass per branch (n=200). The alectorioid/foliose biomass ratio increased from 0·149 at 2–3 m to 0·316 at 5–6 m. Site factors reflecting openness of the canopy were computed for the branch at 2–3 m in all trees. The alectorioid/foliose biomass ratio increased significantly with the indirect site factors, suggesting that light, or factors associated with light, determine the balance between these two growth forms in tree canopies. Within the alectorioid biomass component, genera with usnic acid (Alectoria, Usnea) decreased with height, whereas the genus Bryoria with melanic pigments increased. According to the literature, dark melanic pigments have higher visible light screening efficiency than the yellowish usnic acid. Such patterns suggest a functional role for cortical pigments in the niche differentiation of alectorioid lichens.

Sunscreening fungal pigments influence the vertical gradient of pendulous lichens in boreal forest canopies

“…1b) and/or Usnea on lower, often defoliated branches (Campbell and Coxson 2001, Benson and Coxson 2002, Coxson and Coyle 2003. In Norwegian boreal forests, the biomass of Bryoria increased by a factor of 1.6 from 2-3 m to 5-6 m above the ground, with a concurrent decline (to 61%) in Alectoria and Usnea (Gauslaa et al 2008); their sites are in the same bioclimatic region as our Norwegian site. The mechanism behind this niche partitioning is poorly understood, but various factors are apparently involved.…”

Site factors controlling epiphytic lichen abundance in northern coniferous forests

“…Forests at the forest-steppe ecotone at the southern fringe of the central Siberian taiga, however, show a gradient where the trees at the highly sun-exposed forest line to the steppe are inhabited by epiphytes producing effective sunscreens, including usnic acid and melanins, whereas lichens with less efficient photoprotection, including atranorin-containing species, increase with increasing distance from the forest edge . Gauslaa et al (2008) discussed the possibility that the vertical zonation of alectorioid lichens within the canopy of boreal forests might be due to differences in the light-screening efficiency of cortical pigments between different genera (usnic acid in Alectoria and Usnea versus melanins in Bryoria).…”

Vertical distribution, nitrogen content, and natural 15n and 13c abundance of epiphytic macrolichen functional groups and soil in sub-boreal spruce forests of central British Columbia.

“…A previous study found relationships between lichen growth and site factors reflecting the openness o f the canopy (Gauslaa et al, 2008). In that study, main branches were cut down from two height intervals on each tree to quantify epiphytic lichen biomass.…”

“…There are microclimatic gradients in moisture, temperature, light, and nutrient availability, all which could be influencing the growth of certain types of lichen functional groups at a certain height (Gaio-Oliveira et al, 2004;Gauslaa et al, 2007). Branch length measurements could have been taken, as branch size is an important predictor for epiphytic lichen biomass (Gauslaa et al, 2008). Finally, forest structure, age, site conditions, weather 52 patterns, disturbance regimes, and ground species composition may also be determining factors for epiphytic lichen biomass presence and abundance (Pipp et al, 2001).…”

“…Lower canopy positions, though often less prone to desiccation, are often lightlimiting for photosynthesis. Gauslaa et al (2008) found that genera with usnic acid such as Alectoria decreased with height while genera with melanic pigments such as Bryoria increased with height because dark melanic pigments have higher visible light screening efficiency.…”