Estimation of life history in corticolous lichens by zonation

An even greater challenge, as explained above, is that the gradients change position with respect to a colonization site as the tree grows. [...]supposing a site at a certain distance from the shoot tip offers the best conditions for spore attachment of a certain lichen species; thallus establishment will preferentially begin here but conditions at this colonization site will eventually change so that further recruitment becomes unlikely and the growth of the existing thallus inhibited. [...]we found rather few lichen taxa after 47 years of tree development (Table 1). Maximum water content of the bark samples differed markedly with age among tree species (Fig. 2), with a steep decrease in Abies and Pseudotsuga and almost stable values up the stem in Quercus. [...]water content in Quercus differed significantly from conifer bark (both species), both at the treetops and in the old stem bark (P0·05). [...]the physical bark features could not offer a unique explanation, either for the preferred lichen colonization on Quercus compared to the conifers or for their distribution up the trunks.