Swedish Forest Research Articles

Possibility to implement invasive species control in Swedish forests

Invasive alien species constitute an increasing risk to forestry, as indeed to natural systems in general. This study reviews the legislative framework governing invasive species in the EU and Sweden, drawing upon both a legal analysis and interviews with main national level agencies responsible for implementing this framework. The study concludes that EU and Sweden are limited in how well they can act on invasive species, in particular because of the weak interpretation of the precautionary principle in the World Trade Organisation and Sanitary and Phytosanitary agreements. In the Swedish case, this interpretation also conflicts with the stronger interpretation of the precautionary principle under the Swedish Environmental Code, which could in itself provide for stronger possibilities to act on invasive species.

Broad-scale distribution of epiphytic hair lichens correlates more with climate and nitrogen deposition than with forest structure

Hair lichens are strongly influenced by forest structure at local scales, but their broad-scale distributions are less understood. We compared the occurrence and length of Alectoria sarmentosa (Ach.) Ach., Bryoria spp., and Usnea spp. in the lower canopy of > 5000 Picea abies (L.) Karst. trees within the National Forest Inventory across all productive forest in Sweden. We used logistic regression to analyse how climate, nitrogen deposition, and forest variables influence lichen occurrence. Distributions overlapped, but the distribution of Bryoria was more northern and that of Usnea was more southern, with Alectoria’s distribution being intermediate. Lichen length increased towards northern regions, indicating better conditions for biomass accumulation. Logistic regression models had the highest pseudo R2 value for Bryoria, followed by Alectoria. Temperature and nitrogen deposition had higher explanatory power than precipitation and forest variables. Multiple logistic regressions suggest that lichen genera respond differently to increases in several variables. Warming decreased the odds for Bryoria occurrence at all temperatures. Corresponding odds for Alectoria and Usnea decreased in warmer climates, but in colder climates, they increased. Nitrogen addition decreased the odds for Alectoria and Usnea occurrence under high deposition, but under low deposition, the odds increased. Our analyses suggest major shifts in the broad-scale distribution of hair lichens with changes in climate, nitrogen deposition, and forest management.

Linnebjer—A South Swedish Oak Forest and Meadow Area—Revisited after Half a Century

An oak forest and three wet meadows/fens were reinvestigated after 50 years concerning tree vitality, biomass and productivity, and soil chemistry. Sulphur and nitrogen deposition has changed dramatically during these years, and the aim was to analyse the differences in both the oak forest and the open field ecosystems. Trees were re-measured and soil profiles were resampled. Important visible changes in the oak forest were stated concerning the vitality of oaks. Aboveground there was a decrease in tree biomass, production and litter fall, but a huge increase in standing dead logs. During the years, the deposition of sulphur had decreased drastically, but nitrogen deposition was still high. Soil acidification in the forest had decreased, reflected in an increased base saturation in the forest, in spite of slightly lowered pH-values. Strongly increased amounts of exchangeable Ca and Mg now appeared in the forest soil, and a substantial transport of calcium and magnesium had obviously taken place from the forest soil to the meadow and fens during the years. However, the most important soil change was the accumulation of organic matter. The increased accumulation of organic matter in turn meant increased amounts of colloid particles and microsites for ion exchange in the soil. This favoured 2-valence base cations, and especially Ca and Mg that increased very much in all the studied ecosystems. Carbon as well as nitrogen had strongly increased in the forest, meadow and fen soils. This was interpreted as a natural result of increased vegetation growth due to high nitrogen deposition, increased global annual temperature and increased carbon dioxide concentration in air. It was concluded that the decreased deposition of sulphur had had a positive effect on soil chemistry, and that the deposition of nitrogen probably had stimulated vegetation growth in general, and contributed to increased amount of organic matter in the soils. However, in this studied oak forest, the decreased vitality and many killed trees were also suspected to be a result of high nitrogen deposition. Obviously increased tree growth was counteracted by decreased stress resistance, and increased appearance of pathogens in the oak trees.

The Forest of Our Lives: In and Out of Political Ecology

In this article, I seek to bring together a number of environmental histories to think about the place of forest in our lives. It is partly autobiographical in the sense that it concerns forest issues that I, for various reasons, have been entangled with recently. These are the making of carbon (REDD+) forests in Northeast India, preservation of the urban forests and planting of indigenous trees in Karura forests in Nairobi, Kenya, and the transformation of Swedish forests into vast industrial plantations. I come to these issues with little knowledge about the forest ecology or the flora and fauna, as such, but rather as a scholar with earlier experience of analysis of the social and political dynamics involved in conflicts over forests, that is, how differently powered actors seek to appropriate, stake claims to or control the forest. Hence, my point of departure and analytical framework is largely that of political ecology. In a conversation about the work of the anthropologist Brian Morris, I will point to the thinness of such an approach and open up aspects that are critical to Morris' way of engaging with the interactions of people, plants, insects, and animals. This, I will argue, is a truly grounded environmental anthropology.

Adaptation of Forest Management Regimes in Southern Sweden to Increased Risks Associated with Climate Change

Even though the growth rates of most tree species in Sweden is expected to increase in the near future as a result of climate change, increased risks of damage by storms and various pests and pathogens, notably root rot and bark beetles, may also occur. Thus, forest management practices such as changes to thinning regimes, reductions in rotation lengths, and switching to other species (native or exotic) may represent adaptive management strategies to increase the resistance and resilience of Swedish forests to climate change. Clearly, thorough analyses examining the effects of anticipated climatic changes on damage levels, and the potentially relieving effects of possible management adaptations are needed before implementing such changes. In this study, damage caused by storms, root rot and bark beetles (single and in various combinations) under selected climate and management scenarios were simulated in Norway spruce (Pice abies L. Karst) stands. The results indicate that reductions in thinning intensity and rotation lengths could improve both volume production and profitability in southern Sweden. In addition, cultivation of rapidly growing species, such as hybrid larch (Larix × marschlinsii Coaz.) and hybrid aspen (Populus tremula L. × P. tremuloides Michx.), could be as profitable as Norway spruce cultivation, or even more profitable. However, slow-growing species, such as Silver birch (Betula pendula Roth), Downy birch (Betula pubescens Ehrh.) and European beech (Fagus sylvatica L.) indicated low economic output in terms of Land Expectation Value.

Fostering a flexible forest: Challenges and strategies in the advisory practice of a deregulated forest management system

In deregulated forest management systems, social norms, knowledge dissemination and communication are pivotal for guiding forest owners' actions. This presents a challenge to national forest agencies charged with the task of translating forest policy into practice. Drawing on interviews with forest consultants employed by the Swedish Forest Agency, this paper discusses the challenges present in everyday advisory practice, how they are dealt with, and possible implications for forest policy. Four main challenges are identified: climate change; the heterogeneity of forest owners; resource constraints and funding cutbacks; and competing and conflicting advice. The analysis finds that the forest consultants have developed the following professional capacities to meet these challenges: articulating uncertainties, advocating risk diversification, and using historical references to handle the long-term risk associated with climate change; contextualizing the advice to meet the needs of a heterogeneous group of forest owners; and organizational decoupling, whereby consultants prioritize advisory activities at the expense of other tasks. The study concludes by discussing the implications of these strategies for the forest consultants and forest policy but also what can be learned from the Swedish experience.

Storm disturbances in a Swedish forest—A case study comparing monitoring and modelling

A Norway spruce (Picea abies Karst) forest site in southwest Sweden was chosen to study the effects of storm disturbances over the period 1997–2009, during which two storms, ‘Lothar’ (December 1999) and ‘Gudrun’ (January 2005), affected the area. Monitored deposition data, soil water chemistry data and forest inventory data were compared with the predictions of an integrated ecosystem model, ForSAFE, in an effort to reveal and understand the effects of storms on acidification/recovery in forest soils. Both storms caused windthrow loss leading to increased nitrate and sulphate concentrations in soil water as a result of stimulated mineralization. Lothar led to increased concentrations of Na+, Mg2+, and Cl− in soil water due to sea-salt episode. No general sea-salt episode was seen following Gudrun, but small sea-salt episodes were observed in 2007 and 2008. Each sea-salt episode caused a temporary decrease of pH, and a subsequent recovery, but overall, the soil water pH decreased from 4.54 to 3.86 after Lothar. Modelling suggested that the site was recovering from acidification from 1990s, and would continue to recover in future. Both modelled and monitored data showed that storm caused disturbances in the recovery; monitored data even suggested that soil acidification happened due to storm disturbances. Sea-salt episode does not increase soil acidity in the long term, and will probably decrease the soil acidity by replenishing the base saturation. The modelled data also suggested that storms with only windthrow would not have effects on soil acidification recovery in the long term, but they may influence the soil fertility by losses of base cations.

Evidence for different drivers behind long‐term decline and depression of density in cyclic voles

AbstractDecline and long‐term depression of mean densities of the grey‐sided vole (Myodes rufocanus) and the field vole (Microtus agrestis) have occurred in managed forest landscapes of Sweden since the 1970s. Generally poor over‐winter survival during a period with mild winters suggested a common climatic driver, but other explanations exist. Here we explore the response of the grey‐sided vole, preferring forested habitats, and the field vole, preferring open habitats, to clear‐cutting of old forest in Sweden. The cumulated impact from long‐term clear‐cutting explained local disappearances of the grey‐sided vole. Maintained connectivity of old forest to stone fields was important for local population survival, since no such populations disappeared. For the grey‐sided vole, it is probable that climate is not the dominating driver due to different timing of the decline in our study area. Instead, habitat loss is concluded as being a potential cause of the decline in mean density and depression of grey‐sided vole densities. The long‐lasting depression of field vole densities, despite favourable landscape changes, suggests action of another strong driver. A recent field vole recovery, essentially back to pre‐decline densities and distribution, coincided with favourable winter/snow conditions, suggesting a climatic driver in this case.

Not erroneous but cautious conclusions about the potential effect of climate change on the geographical distribution of insect pest species in the Swedish boreal forest. Response to Björklund et al. (2015)

ABSTRACTWe argue that the conclusions drawn from the paper “The potential effect of climate change on the geographical distribution of insect pest species in the Swedish boreal forest”, published in the Scandinavian Journal of Forest Research were not erroneous as stated by a letter published in the same journal by Björklund et al. (2015. Erroneous conclusions about current geographical distribution and future expansion of forest insects in Northern Sweden: Comments on Hof and Svahlin (2015). Scand. J. Forest Res)”, but cautious. We regret possible underestimations caused by lack of occurrence records for some species for some areas. However, basing predictions of the impact of future climate change on the distribution of species on current range maps likely leads to grave overestimations of future range predictions since current range maps assume species are homogenously distributed throughout the landscape, which is often not the case. We argue that underestimating the distribution range of pest species rather than overestimating their distribution pinpoints areas that may need extra attention in future better, and therefore chose to be cautious rather than bold. We further like to stress that one should always be aware of possible insect outbreaks throughout the region, not only because predictions may underestimate the future distribution of species but also since the location and likelihood of insect pest outbreaks is not only determined by climatic factors.

Forest discourses and the role of planning-related perspectives: the case of Sweden

Forest use in Sweden may be seen as constituting an essentially conflicted area, in which a number of actors position themselves. Based on a review of policy documents, this study reviews discourses on forest amongst major organisational actors between 2001 and 2011, with the aim of discussing the ways in which discourse may have changed following increasing criticism of the previously dominating production paradigm during the period. The study also discusses the ways in which forest discourses at present may also exclude areas that are relevant to forest planning. Results illustrates the continuous role of, on the one hand, production and private ownership discourses among the forest industry, and, on the other, conservation and public access discourses, among environmental and other NGOs. Large differences thus continue to exist despite the double aim towards production and protection in Swedish forest law. Areas that are not directly related to this nexus although related to land use at large, such as municipal planning, on the other hand, are largely absent from discourse even if, for instance, shore planning and wind power issues that are related to municipal planning are taken up.

Combining scientific and stakeholder knowledge in future scenario development — A forest landscape case study in northern Sweden

Northern Swedish forests provide multiple ecosystem services. Integrating these values into the forest planning process frequently requires that not only forest owners but also other stakeholders be involved. The objective of this study is to assess the potential of future scenario development as a tool in forest planning. In a case study of the Vilhelmina municipality in northern Sweden, forest owners and stakeholders were interviewed, and a workshop was held to discuss important factors for the future development of the local landscape regarding ecological, socioeconomic and political issues. Combined with a researcher-conducted process, this resulted in three alternative scenarios. We conclude that the scenario development process has produced information that can be used in forest planning. The participatory element of the scenario development process could be extended further to enhance communication, learning and knowledge exchange. The participants' contribution to the scenario construction could also be elaborated, e.g., by further involving stakeholders in the formulation of alternative future manifestations and in the elaboration of scenarios. To achieve this, it is necessary to adapt the quantitative methods to the participatory situation, to foster discussion qualities, to secure representation and increase motivation for participation in different ways.

Structural changes in protected forests in Sweden: implications for conservation functionality

Protected forest areas (PFAs) are key features of biodiversity conservation, and knowledge about long-term development is crucial in evaluating their efficiency and management needs. Longitudinal data on forest structure in PFAs is uncommon and often from small areas. Here we use data from the Swedish National Forest Inventory to study changes in more than 750 000 ha of PFAs over 60 years. Structures important for biodiversity, e.g., number of large trees and the volume of hard deadwood, including both standing and down wood, have more than doubled. The initial volume of deadwood, however, was very low. The overall tree species composition was stable over time, and only among the largest trees were there indications of a shift towards the late successional Norway spruce (Picea abies (L.) Karst.). Deadwood increased independent of species, size of wood, and site characteristics. This increase was positively related to the volume of living trees and forest age. We conclude that Swedish PFAs, in the absence of active management and under fire suppression at the landscape scale, develop structural components that are crucial for conservation of biodiversity. However, although tree species composition appears stable, present disturbance regimes in the PFAs are considerably different from those in naturally dynamic forests, which may have implications for long-term biodiversity maintenance.

Carbon storage and nutrient mobilization from soil minerals by deep roots and rhizospheres

Roots mobilize nutrients via deep soil penetration and rhizosphere processes inducing weathering of primary minerals. These processes contribute to C transfer to soils and to tree nutrition. Assessments of these characteristics and processes of root systems are important for understanding long-term supplies of nutrient elements essential for forest growth and resilience. Research and techniques have significantly advanced since Olof Tamm’s 1934 “base mineral index” for Swedish forest soils, and the basic nutrient budget estimates for whole-tree harvesting systems of the 1970s. Recent research in areas that include some of the world’s most productive and intensively managed forests, including Brazil and the USA, has shown that root systems are often several meters in depth, and often extend deeper than soil is sampled. Large amounts of carbon are also sometimes stored at depth. Other recent studies on potential release of nutrients due to chemical weathering indicate the importance of root access to deep soil layers. Nutrient release profiles clearly indicate depletion in the top layers and a much higher potential in B and C horizons. Reviewing potential sustainability of nutrient supplies for biomass harvesting and other intensive forest management systems will advance understanding of these important ecosystem properties, processes and services relevant for management.

The potential effect of climate change on the geographical distribution of insect pest species in the Swedish boreal forest

ABSTRACTWith the expected rising temperatures, outbreaks of insect pests may be more frequent, which can have large consequences on forest ecosystems and may therefore negatively affect the forestry sector. In order to be better able to predict where, but not if, outbreaks may occur in future we investigated the potential future (2070) geographical distribution of 30 prospective insect pest species (Coleoptera and Lepidoptera) by applying species distribution modelling. We also assessed the geographical extent to which the boreal forest in Sweden may be affected. We found that numerous species may experience large increases in their potential distribution in future, which may result in outbreaks in “new” areas. It is therefore likely that more trees will be infested by pests in future, which may have large implications for the Swedish forestry sector.

Dissimilar framings of forest biodiversity preservation: Uncertainty and legal ambiguity as contributing factors

Controversies over forestry and environmental issues, including biodiversity, are common. Theory suggests that uncertainty may play a major role in framing biodiversity and its preservation. This paper examines written statements on biodiversity preservation published by two major Swedish organizations, i.e., the Swedish Forest Industries Federation and the Swedish Society for Nature Conservation, with different interests in forest use. Frame analysis suggests that when the actors pursue a certain policy course, both biodiversity-related uncertainty and lack of regulatory clarity are important factors contributing to dissimilar framings. This case study supports the general understanding that biodiversity-related uncertainty can have important implications for biodiversity preservation, in this case, via forest policy and legislation. Scientific uncertainty may allow actors with dissimilar interests in an issue to justify their standpoints. To successfully manage forest biodiversity in the future, legal frameworks must increasingly find ways to accommodate scientific uncertainty, and models must be developed in which stakeholders' diverging interests and values address uncertainties via dialogue.

The climate effect of increased forest bioenergy use in Sweden: evaluation at different spatial and temporal scales

Bioenergy from boreal forests managed for productive purposes (e.g., pulp, timber) is commonly held to offer attractive options for climate change mitigation. However, this view has been challenged in recent years. Carbon balances, cumulative radiative forcing, and average global temperature change have been calculated for a variety of bioenergy management regimes in Swedish forests, and the results support the view that an increased use of forest biomass for energy in Sweden can contribute to climate change mitigation, although methodological (e.g., spatial scales) and parameter value choices influence the results significantly. We show that the climate effect of forest‐based bioenergy depends on the forest ecosystems and management, including biomass extraction for bioenergy and other products, and how this management changes in response to anticipated market demands; and on the energy system effects, which determine the fossil carbon displacement and other greenhouse gas (GHG) mitigation effects of using forest biomass for bioenergy and other purposes. The public and private sectors are advised to consider information from comprehensive analyses that provide insights about energy and forest systems in the context of evolving forest product markets, alternative policy options, and energy technology pathways in their decision‐making processes. WIREs Energy Environ 2016, 5:351–369. doi: 10.1002/wene.178This article is categorized under: Bioenergy > Climate and Environment

Exclosures can favour natural regeneration of oak after conservation-oriented thinning in mixed forests in Sweden: A 10-year study

Oak trees are biodiversity hotspots in many landscapes and provide habitats for several organism groups, including species that are rare or threatened by extinction. Oak regeneration in the northern hemisphere is often poor, which is a serious problem in many oak-rich conservation forests. Competition from other vegetation and browsing by ungulates are two factors that limit oak regeneration. In 13 mixed oak-rich forests with high values for biodiversity we tested conservation-oriented thinning. Trees and shrubs were harvested for biofuel, but the main aim was to favour oak regeneration and biodiversity. On average, 23% of the initial basal area was removed during the winter 2002/2003. After thinning, we set up exclosures to protect oak seedlings from browsing. In 2012, after ten growing seasons, the exclosures had favoured regeneration of oak by reducing ungulate browsing, though the effect was weak. Tall oak saplings (>130cm) were present in exclosures at five sites, and no such new stems were recorded in control plots with browsing. These five sites were characterized by higher canopy openness, and probably higher light availability, compared to the other sites. Other broadleaves, and especially shrubs, increased much more in density and height than oaks, in both exclosures and control plots. Thus, conservation-oriented thinning in combination with fences to protect oak seedlings from browsing ungulates, increased oak regeneration in the mixed conservation forests, but control of competing understory vegetation in exclosures is probably also needed.

Integration of next-generation biofuel production in the Swedish forest industry – A geographically explicit approach

The geographic locations of biofuel production facilities should be strategically chosen in order to minimise the total cost of using biofuels. Proximity to biomass resources, possibilities for integration, and distance to biofuel users are aspects that need to be considered. In this paper, the geographically explicit optimisation model BeWhere Sweden was used to investigate the future production of next-generation biofuels from forest biomass in Sweden. A focus was placed on the integration of biofuel production with the existing forest industry, as well as on how different parameters affect biofuel production costs, the choice of technologies and biofuels, and the localisation of new biofuel plants. Six examples of different biofuel routes were considered. A methodology was developed considering detailed, site-specific conditions for potential host industries. The results show that the cost of biomass and the biofuel plant capital cost generally dominate the biofuel cost, but the cost for biomass transportation and biofuel distribution can also have a significant impact. DME produced via black liquor gasification (naturally integrated with chemical pulp mills) and SNG produced via solid biomass gasification (mainly integrated with sawmills), dominate the solutions. The distribution of these technology cases varies depending on a number of parameters, including criteria for sizing biofuel plants, the electricity price, the biofuel distribution cost and the cost of biomass, and is sensitive to changes in these parameters. Generally, plants with low specific investment costs (i.e., high biofuel production) and/or plants with low specific biomass transportation costs occur most frequently in the solutions. Because these properties often vary significantly among biofuel production facilities at different host industry sites of the same type, the results show the advantage of including site-specific data in this type of model. (C) 2015 Elsevier Ltd. All rights reserved.

Reviewing ALOS PALSAR Backscatter Observations for Stem Volume Retrieval in Swedish Forest

Between 2006 and 2011, the Advanced Land Observing Satellite (ALOS) Phased Array L-type Synthetic Aperture Radar (PALSAR) instrument acquired multi-temporal datasets under several environmental conditions and multiple configurations of look angle and polarization. The extensive archive of SAR backscatter observations over the forest test sites of Krycklan (boreal) and Remningstorp (hemi-boreal), Sweden, was used to assess the retrieval of stem volume at stand level. The retrieval was based on the inversion of a simple Water Cloud Model with gaps; single estimates of stem volume are then combined to obtain the final multi-temporal estimate. The model matched the relationship between the SAR backscatter and the stem volume under all configurations. The retrieval relative Root Mean Square Error (RMSE) differed depending upon environmental conditions, polarization and look angle. Stem volume was best retrieved in Krycklan using only HV-polarized data acquired under unfrozen conditions with a look angle of 34.3° (relative RMSE: 44.0%). In Remningstorp, the smallest error was obtained using only HH-polarized data acquired under predominantly frozen conditions with a look angle of 34.3° (relative RMSE: 35.1%). The relative RMSE was below 30% for stands >20 ha, suggesting high accuracy of ALOS PALSAR estimates of stem volumes aggregated at moderate resolution.

Community occupancy before-after-control-impact (CO-BACI) analysis of Hurricane Gudrun on Swedish forest birds.

Resilience of ecological communities to perturbation is important in the face of increased global change from anthropogenic stressors. Monitoring is required to detect the impact of, and recovery from, perturbations, and before-after-control-impact (BACI) analysis provides a powerful framework in this regard. However, species in a community are not observed with perfect detection, and occupancy analysis is required to correct for imperfect detectability of species. We present a Bayesian community occupancy before-after-control-impact (CO-BACI) framework to monitor ecological community response to perturbation when constituent species are imperfectly detected. We test the power of the model to detect changes in community composition following an acute perturbation with simulation. We then apply the model to a study of the impact of a large hurricane on the forest bird community of Sweden, using data from the national bird survey scheme. Although simulation shows the model can detect changes in community occupancy following an acute perturbation, application to a Swedish forest bird community following a major hurricane detected no change in community occupancy despite widespread forest loss. Birds with landscape occupancy less than 50% required correcting for detectability. We conclude that CO-BACI analysis is a useful tool that can incorporate rare species in analyses and detect occupancy changes in ecological communities following perturbation, but, because it does not include abundance, some impacts may be overlooked.