Tree selection by the endangered beetle <Emphasis Type="Italic">Rosalia alpina</Emphasis> in a lapsed pollard beech forest

Abandoned pollard beech forests are particular habitats that may require special conservation efforts to preserve the endangered beetle Rosalia alpina, a model species whose protection may perpetuate the habitat of many other saproxylic species. Forest use can determine the tree selection and population size of R. alpina, variables previously not researched in pollard forests. Selected tree traits and population size, indicated by presence of adult specimens and recent exit holes, were determined in a pollard beech forest before the implementation of habitat manipulations targeted to preserve the species. Multivariate analysis showed tree condition (living, snag, fallen) and clearing size and aspect as influential variables, with the former explaining more variance than the latter. R. alpina positively selected pollard snags and trees located in big and dry clearings, avoiding those in small clearings or shaded areas. Snags showed most adults (90 %) and recent emergence holes (84 %). Distance to the nearest occupied tree, trunk diameter, bark thickness and presence of sap leaks had no effect on the occurrence of R. alpina. Population size was estimated in 0.1 individuals day^?1 ha^?1, and 38 % of available habitat trees showed exit holes, values lower than those observed in other European countries. These results show the need to start re-pollardings in the forest to extend pollard standing life and enhance exposure to sunlight. Pinpointing pollard snags and clearing the surrounding vegetation are recommended as the first measures to be taken in order to favor R. alpina populations on pollard stands with closed canopies.