Lichen litter decomposition in Nothofagus forest of northern Patagonia: biomass and chemical changes over time

In northern Patagonia, macrolichens form species-rich and abundant epiphytic communities in southern beech forests. Five of the most abundant lichen species in the litter were selected in order to study mass loss rate and changes in mineral composition over time. The litter bag method was applied to the foliose lichens Pseudocyphellaria faveolata, Pseudocyphellaria flavicans, Nephroma antarcticum, Platismatia glauca and the fruticose Protousnea magellanica. Decomposition was measured over 550- and 600-day periods, starting in early and late summer, respectively. Mass loss after these periods varied from 30 to 82%. The decomposition rate between species differed from a half-life of 2.9 years in Pseudocyphellaria faveolata to 0.8 years in Protousnea magellanica and Plastismatia glauca. Samples deposited in early summer had a higher initial mass loss compared to samples deposited in late summer. After this initial loss, all species showed a similar temporal pattern with higher decomposition rates in winter and spring than in summer and fall. Pseudocyphellaria faveolata, Pseudocyphellaria flavicans and Nephroma antarcticum contain nitrogen-fixing cyanobacteria and had a considerably higher N concentration and lower C/N ratio than Platismatia glauca and Protousnea magellanica. However, the latter species had a faster mass loss. Changes in macronutrient concentrations were small apart from a rapid loss of P and K in Pseudocyphellaria spp. and increasing Ca and Mg concentrations in Platismatia glauca and Protousnea magellanica. We conclude that seasonal climatic variations partly control the decomposition pattern but that the time of litterfall strongly influences the initial decay rate.