Old-Growth Forests in the High Coast Region in Sweden and Active Management in Forest Set-Asides
Sammanfattning: In today´s intensively managed landscape, very few forests with old-growth characteristics and little human impact exist. One of the rare exceptions is pine forests on rocky soils, a forest type which has probably escaped extensive human use because of its low productivity. Our objective was to investigate the structure, dynamics, and history as well as the abundance and richness of wood-inhabiting fungi in these types of forest. We chose rocky pine forests situated in the High Coast Region to exemplify this forest type since the regional County Administration had already made surveys of the conservation value in 26 rocky pine forest stands in this region. We investigated the forests by recording tree species and measuring tree size and age in eight of the stands that were ranked with the highest conservation value. We also sampled dead wood to examine time since death and we sampled living and dead trees with fire scars to date fires. In addition, we made an inventory of wood-inhabiting fruiting bodies and took woodchip samples from logs to learn (by DNA analysis) whether five rare wood inhabiting fungi species were present as mycelia in logs.We found that rocky pine forests in the High Coast Region have a multi-sizedand multi-aged structure and old pine trees (approximately 13 ha-1 older than 300 years) are present. Fire has been common (an average of 42 years betweenfires) but they were likely to have been low-intense and small. Although the amount of dead wood is relatively low (4.4 m3 ha-1 on average) compared to many other boreal forests with old-growth characteristics, the share of deadwood of the total tree basal area (18%) was in line with other pine forests with low levels of human impact. The low dead wood volume is therefore likely to be an effect of the low productivity rather than dead wood extraction by humans. We also discovered that dead wood can be present for a really longtime without totally decomposing; we found logs and snags that had been dead for 500 years. This continuity of dead wood might be important for organisms dependent on dead wood as a substrate and even though we found that the species richness of wood-inhabiting fungi was somewhat low, we did find some rare species. Cinereomyces lenis and Hyphodontia halonata were present as fruiting bodies and we also found Antrodia albobrunnea, Antrodiainfirma, Crustoderma corneum and Anomoporia kamtschatica present as myceliain logs.The second part of this thesis reports two systematic reviews studying the effects of active management on the biodiversity in boreal and temperate forests. A systematic review follows certain guidelines and aims to compile the evidence base in well-defined topics, so that managers, researchers and policymakers can gain access to a high-quality compilation of current research. In our systematic map, we found almost 800 relevant papers but the set of papers turned out to be too heterogenic (many intervention types, e.g. thinning, burning, grazing and many types of outcomes) to allow any quantitative analysis. However, this map identified knowledge gaps and several detailed research questions that had sufficient data to provide aquantitative statistical analysis.One of these questions was: What is the impact of dead wood creation or addition on dead wood-dependent species? We focused on three types of interventions: creation of dead wood, addition of dead wood from elsewhere and prescribed burning. The selected outcomes were: saproxylic insects (rareand pest species), saproxylic fungi (rare species), ground-living insects and cavity-nesting birds. There was no significant negative effect on any of the investigated species groups but a positive effect on the abundance and richness of saproxylic insects and fungi. We also found that, although the amount of dead wood created was much less (50%) with prescribed burning, the abundance and richness of saproxylic insects showed similar positive effects to those of other intervention methods. A likely explanation for this is that burning results in a diversity of dead wood of various levels of quality (e.g. dense and/or charred wood), which creates a heterogeneity of dead woodtypes having a positive effect on the diversity of species dependent on deadwood. In summary, active management generally has a positive effect on biodiversity but the choice of management type should always be made carefully, and in consideration of the effect you want to achieve. In addition, there is a need for more long-term primary studies and more species groups in more geographical areas need to be incorporated so that the systematic reviews in this field will be even more informative in the future.
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