The n-alkane concentrations in buds and leaves of browsed broadleaf trees

The concentration of n-alkanes in the cuticular wax of plants can be used t o estimate the composition of the diet selected by free-ranging animals. Th e aims of this study were to characterize the n-alkane profiles of developi ng leaves and evaluate the degree of chemical discrimination between six br owsed broadleaf tree species: European ash (Fraxinus excelsior L.): floweri ng ash (Fraxinus or nus L.), hornbeam (Carpinus betulus L.), hazel (Corylus avellana L.), mountain ash (Sorbus aucuparia L.) and beech (Fagus sylvatic a L). The effect of the stage of development was examined by considering fi ve different vegetative stages: dormant bud (DB), late bud (LB), young leaf (YL): mature leaf(ML) and senescing leaf(SL). Five samples per each vegeta tive stage and species, gathered in a mixed woodland of the Italian Eastern Alps between February and October, were analysed for their n-alkane concen trations (C-23-C-30). The residual coefficient of variation was 15.5 % on average for the individ ual n-alkanes considered. There were noticeable differences in individual a nd total n-alkanes content between species. In particular, C-27 was the pre dominant n-alkane in beech and C-33 was found in high proportions in the tw o species of Fraxinus; hazel and flowering ash had a higher total n-alkanes content than the overall mean, while the lowest values were found in hornb eam and beech. The n-alkane profile also underwent important changes during the vegetative development, with different extent and direction according to the species. In the three successive leaf stages, a tendency for a progr essive increase in the longest chain homologues was observed. In any case, the young leaf stage differed most from the contiguous stages. Canonical discriminant analysis indicated that the n-alkane profile of buds and leaves were mathematically distinguishable and the chemical difference s between species were persistent over the plant vegetative development.