Influence of substrate age and quality on species diversity oflichens and bryophytes on stumps

摘要

Stumps from the last felling constitute a large proportion of dead wood in youngmanaged forests. Yet, the knowledge of the diversity of stump-inhabiting organisms ispoor. We studied the importance of substrate age and quality to lichen and bryophytediversity on the cut surface of stumps in south-central Sweden. In total, we found 53lichens and 35 bryophytes on 449 Norway spruce stumps in a forest stand chronosequenceof four age classes: 4-5,8-9,12-13 and 16-18 years old stands. The influence of substrateage and substrate quality on species diversity differed between lichens and bryophytes.Lichen species richness was higher for age classes 2-4 compared to age class 1, whereasbryophyte richness was higher in age classes 3-4 than in 1. Further, lichen richnessincreased with increasing stump height and the presence of surface structural components(chairs and levels), which together with decay also influenced lichen species composition.Conversely, increasing stump height and the presence of levels decreased bryophyterichness, which in turn increased with increasing decay, surface area and number ofsurrounding trees and shrubs. Only decay explained differences in bryophyte speciescomposition. Stumps in this region seem more important to overall lichen diversity,because there were on average more lichen species per stump and we only found commonbryophytes but several uncommon lichens. The different responses of lichens andbryophytes to age and substrate variables indicates, however, the importance of includingseveral organism groups in species diversity studies of dead wood.