Epsilon Archive for Student Projects

Abstract

Dead wood is important for many species. The amount of coarse dead wood (diameter >10 cm) is much lower in managed forest than in unmanaged forests. Stumps constitute the largest proportion of the volume of coarse dead wood in managed forests. Since stump harvest for biofuel may increase, the amount of dead wood will decrease even more, which may threaten biodiversity. The first aim of this study was to compare the amounts of fine woody debris (FWD, <10 cm in diameter) and coarse woody debris (CWD), in young managed forest stands. The second aim was to investigate if epixylic lichen and bryophyte occurrences were affected by substrate qualities. In seven stands (9-16 years old) in the province of Uppland I estimated the amounts of dead wood, and recorded substrate quality variables and occurrence of eight lichen and five bryophyte species. Number of objects and surface area were larger for FWD than CWD, while the volume was higher for CWD. Five of the 13 focal species were found, among which the occurrence probabilities of the lichens Cladonia botrytes, Xylographa parallela and Mycocalicium subtile could be analyzed statistically. C. botrytes only occurred on CWD, and there was a higher probability of occurrence on stumps than on logs. The occurrence probability of X. parallela was higher on CWD than on FWD. For M. subtile the probability of occurrence was not affected by substrate variables. Stumps are important substrates for C. botrytes, which is an argument against stump harvest. If choosing between harvesting slash (i.e. branches and tops) or stumps, this study suggests that stump harvest gives the most negative effects on occurrence probabilities in young managed forest stands of two epixylic lichens. However, more perspectives have to be included to be able to in full evaluate stump harvest.