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- Lindmark, Matilda
(författare)
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Increased resilience in managed boreal forests : Controlling damage by spruce bark beetle and moose in Sweden
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Most of the forests growing in Europe today have been planted, or heavily affected, by humans. This is because the forest industry provides crucial raw materials for diverse products, including timber, pulp and paper, cellulose-based substances and renewable energy sources. However, forest management has turned heterogenic natural forests into homogenous forest stands that are highly susceptible to various kinds of damage. This thesis focuses on moose (Alces alces L.) browsing and attacks by spruce bark beetle (Ips typographus L.), both of which cause large economic losses. Empirically, it is based on field experiments conducted in managed forests in Sweden. Moose browsing on vulnerable top shoots of young pines during wintertime is a substantial problem in northern Europe. My colleagues and I (hereafter we) found that extracts of spruce trees (which moose prefer less than pine) can act as efficient natural browsing repellents.Spruce bark beetles attack spruce (Picea abies) trees throughout Europe. Thus, we also evaluated the field behavior of the beetles exposed to non-host- and fungal volatiles in efforts to identify more efficient ways to protect susceptible spruce stands. In addition, we evaluated the predator:prey ratio between the beetles and Thanasimus predators in representative forest stands, to assist efforts to enhance the biological control of spruce bark beetles in managed forests. Finally, we investigated changes in bacterial communities in wood after attacks by spruce bark beetles to improve knowledge of their ecology.Changes in forest management regime are needed to increase structural and tree species diversity, and thus raise forests’ resilience and ability to cope with ongoing climate change. Results presented in this thesis indicate that changing forest management to increase the variation in tree species variation will enhance the resilience of managed forests, thereby reducing damaging by both moose and spruce bark beetle.
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| 2. |
- Sandström, Jennie
(författare)
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Old-Growth Forests in the High Coast Region in Sweden and Active Management in Forest Set-Asides
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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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| 3. |
- Skytt, Torbjörn, 1964-
(författare)
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Fossil Free or Not - That is the Question
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This is an evaluation of Jämtland County’s ability to achieve its climate targets to reduce greenhouse gas (GHG) emissions with 10% annually, and to become fossil fuel free 2030. There is a risk that the target to become fossil fuel-free, relying primarily on outtake of forest biomass, contradicts with the target in the UN Paris Agreement to keep the global temperature increase below 1.5°C. Neither the GHG emissions reduction target, nor the target to become fossil fuel free, takes forest carbon content into account. To reach the target to become fossil fuel free, forest harvest volumes may need to be increased. This can result in lower short-term net climate benefits than if fossil fuels are substituted to a less extent, and harvest volumes are kept at lower levels. Lower harvest volumes contribute to higher net climate benefits, and in the short term this effect is greater the lower the harvest level. In any case, forest production should be optimized towards products that give high substitution effects from the replacement of other materials. To be able to reach the short-term reductions of GHG emissions, efforts should be made to decrease regional energy demand and general consumption. The transition to new technologies is slow, and is unlikely to contribute to short-term reductions. By the end of 2023, according to the county strategy, the GHG emissions should be max 73% of the emissions by the end of 2019. This is a historically huge reduction. The potential to increase uptake of carbon dioxide in forests should be considered as a complement to the other climate targets. Assessments of social/welfare risks have to be weighed against the risks of increased temperatures, which is challenging, but needs to be done. The complexity of differences in short-term and long-term carbon balance effects makes risk assessments of climate mitigation strategies difficult. Compromises will be required between risks with different time horizons. To rely on techno-optimistic visions increase the risks that the emission reduction target will not be reached. From some perspectives, it is positive to spread techno-optimistic future visions, but there is a risk that we will keep on increasing consumption if we believe that problems with increased atmospheric concentrations of GHG can be solved by continuous consumption of ‘sustainable’ products. A simple 2% rule of thumb is that 2 kg of CO2eq is emitted for each 100 SEK consumed.
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| 4. |
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