Epsilon Open Archive

Abstract

This thesis focuses on distribution and ecology of epiphytic lichens in Nothofagus forests of northwestern Patagonia, Argentina. The general aims were 1) to analyse diversity and abundance of epiphytic lichen vegetation in gradients of stand age and humidity and 2) to study growth rates and decomposition of important macrolichen species. Gradients in biomass and species diversity of epiphytic macrolichen communities are positively correlated to increasing annual precipitation. This pattern was particularly clear for the cyanolichen species of the genus Pseudocyphellaria. Lichen biomass and diversity increases with stand age but colonization of young stands is probably also influenced by the presence of remnant old trees and the distance to old-growth forest. In old-growth-forests, the nitrogen input by N-fixing cyanolichens can be significant, mostly due to the abundance of tripartite Pseudocyphellaria and Nephroma species. Surveys of trunks and litter provide supplementary information. However, future studies should also include surveys of canopy branches in order to give representative information on lichen abundance and diversity. Growth and decomposition showed a similar seasonal pattern with highest rates recorded during winter for all macrolichens analysed. Constantly humid conditions may favour both processes during the winter season. Annual growth rates of Pseudocyphellaria berberina showed a 10-20% increase in biomass. No differences in growth rates depending on transplanting method, phorophyte age or stand age could be found. It is concluded that limitations in dispersal or establishment are more important than stand microclimate for performance of P. berberina in post-fire stands. Cyanolichens with highest nitrogen content showed the lowest decomposition rates, contrary to what was expected. This supports the hypothesis of the presence of an anti-herbivore component in the Lobariaceae family in southern temperate forests. Post-fire sequences are well suited to study effects of disturbance on lichen distributions in Nothofagus forests. Further studies are needed to analyze the effect of gap size and remnant trees on recolonization of epiphytic lichens. Such information will be essential to predict effects of forestry in previously unmanaged forest landscapes.