Epsilon Open Archive

Abstract

Tree retention at forest harvesting aims at promoting biodiversity by increasing structural diversity in managed forests. For this thesis, I have investigated the influence of tree retention on delivery of ecosystem services (wood production and carbon storage) and dead wood (as a proxy for biodiversity). Furthermore, habitat requirements of lichens dependent on dead wood were investigated. The investigation was conducted in 15 Scots pine forest stands with five tree retention levels, in which four categories of trees were retained at similar proportions: green living trees, girdled trees, high-cut stumps and cut trees left on the ground. Three control stands were left untouched. This thesis consists of three studies. In the first, we investigated how tree retention influences the amount and diversity of dead wood, logging productivity during harvest and both present and future income loss for the landowner (given as discounted opportunity costs). In the second, we simulated outputs of merchantable wood, dead wood and carbon stock during a 100-year forest rotation period at stand and landscape scales. At landscape scale, we simulated dead wood volumes and carbon stock under the constraint that landscape size and merchantable wood production were kept constant among scenarios, while retention level and area set aside for conservation varied. In the third study, we investigated how dead wood types (low stumps, snags, logs), wood hardness, wood age and occurrence of fire scars influence the occurrence of dead wood dependent lichens. We found that logging productivity and net incomes from harvest decreased with increasing retention levels, but also that volumes and diversity of dead wood and proportion of undamaged old dead wood increased. Furthermore, at the stand scale, increased retention level increased total carbon storage above and below ground. At the landscape scale, differences in carbon stock and dead wood input were generally small between the scenarios with varying retention levels and set-aside forest area. The lichen species composition differed significantly among the investigated substrates. Many species were highly associated with old and hard wood. Such wood is formed in fire-affected pine forests, but is rare in managed forest. The findings of this thesis could be used to guide future forest management and conservation.