Epsilon Archive for Student Projects

Abstract

A high amount of dead wood is one of the most important prerequisites for high biodiversity on forest land in Sweden. Dead wood is most abundant in young forests, thinned forests, woodland key habitats and protected forest land. In old-growth forests most of the dead wood consists of logs and snags, whilst in managed forests a huge proportion of dead wood is made up of logging residues like stumps and FWD, fine woody debris (< 10 cm diameter). All these different types of dead wood may serve as substrates for epixylic bryophytes and lichens. However, few studies have been conducted on the relative importance of these different fractions of dead wood for the occurrence of bryophytes and lichens, especially when considering dead wood on thinned forest land. The aim of this study was to examine the collected wood supply in thinned forests compared to key habitats. In this study, I compared the amount and composition of dead wood in thinned commercial forests and in woodland key habitats. In a total of 14 stands, seven in each category, all types of dead wood (>1 cm diameter) were studied, on a total of 450 m2 in each stand. Fourteen epixylic bryophytes and lichens were studied to determine what factors influence their occurrence and abundance.

The results showed that, while there were no differences in the volume and in the area of dead wood between thinned forests and woodland key habitats, there was considerable variation between individual stands. What distinguished the former from the latter was the composition of dead wood. Woodland key habitats had, to a greater extent, snags and substrates influenced by litter from deciduous trees. This contributes to a larger variation in wood qualities which in turn can lead to a higher biodiversity. Thinned forests, on the other hand, were characterized by logging residues, whose importance for bryophytes and lichens is still not completely known. As much as 50 % of the dead wood volume in thinned forests consisted of logging residues, while corresponding fractions make up 20 % of the dead wood volume in woodland key habitats. Few species observations were made, which can probably be explained by the fact that many of the studied species are rare, and the investigated area is quite small. Only two species could be analyzed further, Herzogiella seligeri and Xylographa parallella. For H. seligeri no pattern was found. The probability for occurrence of X. parallella on a dead wood substrate increases if the substrate is of CWD type and also with decreasing bark cover or with decreasing cover of pleurocarpous bryophytes.