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The available amount of wood supply is essential for national strategic planning and evaluation of forestry in Sweden. Since Sweden holds a large part of the forests in the European Union and plays a significant role in the global trade of wood-based products, a precise estimate of the potential of the Swedish forest resource is also important in regional and global outlook studies. In this study, we analyse factors influencing the availability and mobilization of wood supply. By comparing data from the Swedish National Forest Inventory with the stand registers of the five largest forest owners in Sweden, we estimate the productive forest area not included in the forest owners' stand databases. Our results show that 0.4 million hectares, or 5% of these large-scale forest owners productive forest area, is outside their stand registers and therefore neither included in their long-term harvesting plans nor in their nature conservation plans. For small-scale forest owners, we analyse the final felling rate during 2004–2020 using satellite imagery to estimate the proportion of properties that abstain from final fellings and thereby could affect the potential mobilization of wood supply. During this period, 32% of the forest properties owned by small-scale forest owners have not done any final felling. These forest estates hold in total 1.1 million hectares of productive forest land or 9% of the area owned by small-scale forest owners. This implies a gap between the potential and realistic estimates for Forest Available for Wood Supply. [ABSTRACT FROM AUTHOR]

Following an almost century-long increase, forest growth in Sweden has abruptly decreased during the last decade. Lower than expected forest biomass trajectories threaten national targets for carbon sequestration and bioeconomy. While climate-related drought is the most likely cause, the critical question is whether this recent growth decline is transient, or the beginning of a new normal where conventional management actions may risk further losses of resilience to water stress. We argue that improved mechanistic insights through better integrated research are urgently needed to avoid worsening the situation and further delaying necessary actions. • After a century of increase, forest growth has abruptly decreased the last decade. • The growth decline threatens national targets for carbon sequestration and bioeconomy. • Climate-related drought is the most likely cause of the recent growth decline. • Improved mechanistic insights are urgently needed through integrated research. [ABSTRACT FROM AUTHOR]

Key message: Using satellite-based maps, Ceccherini et al. (Nature 583:72-77, 2020) report abruptly increasing harvested area estimates in several EU countries beginning in 2015. Using more than 120,000 National Forest Inventory observations to analyze the satellite-based map, we show that it is not harvested area but the map's ability to detect harvested areas that abruptly increases after 2015 in Finland and Sweden. [ABSTRACT FROM AUTHOR]

About 70 million m3 was damaged by the storm Gudrun that hit southern Sweden in January 2005, i.e. almost as much as the normal annual cut for the whole country. To establish any differences in forest state and forest management before and after the storm, measures such as growing stock, annual growth, age-class distribution, choice of species in regeneration and cleaning and thinning activities were studied for the area affected and the area unaffected by the storm. For all analyses, sample plots from the Swedish National Forest Inventory were used. Results based on mean values for the periods 2000–2004/2006–2010/2012–2016 showed that the total growing stock for the damaged area decreased significantly by ~30 million m3 directly after the storm but has now recovered to the same level as before the storm. Therefore, it seems clear that forest owners and forest managers made rational choices when aiming to restore the forest area. As expected , the annually cleaned area and the area in immediate need of cleaning increased significantly in the Gudrun area after the storm. No other significant changes in behaviour to reduce future storm damage risk could be detected. [ABSTRACT FROM AUTHOR]

About three times the annual cut in southern Sweden (Götaland) was damaged by the storm Gudrun in January 2005, i.e. almost as much as the normal annual cut for all of Sweden. To establish any differences in forest management and state before and after the storm, measures such as growing stock volume, age-class distribution, and species composition were analyzed within the damaged area. As a reference the situation before and after the storm within the area in Götaland not damaged by the storm was also analyzed. For all analyses, sample plots from the Swedish National Forest Inventory were used. Results based on mean values for the years 2000–2004/2005–2009 showed that the total growing stock for the damaged area decreased by approximately 30 million m3after the storm. This was mainly caused by a decrease in Norway spruce (Picea abies(L.) H. Karst). Annual growth for pine, spruce, and deciduous trees decreased by 1.8 million m3in the damaged area. This mainly included stands already thinned and not, as expected, in the stands ready for final felling. Also, the proportional area within each of the age classes 21–40, 41–60, and 61–80 years decreased. The storm led to an increased area in immediate need of precommercial thinning. No changes in choice of species when regenerating could be observed. Furthermore, only marginal adaptation by forest owners to future risk of wind throw could be detected. [ABSTRACT FROM AUTHOR]

Highlights: [•] Trees are often left after clearcutting to promote biodiversity. [•] Such retention approaches were introduced large-scale in Sweden about two decades ago. [•] Changes in structural diversity were analyzed with National Forest Inventory data. [•] Dead wood volumes have doubled in forests 0–10years old the last 10years. [•] Numbers of living trees in forests 0–10years old have returned to the 1955 level. [Copyright &y& Elsevier]

Abstract: A storm in January 2005 in southern Sweden (Gudrun) caused large damage to forests, archaeological sites, buildings, power supply, telecommunications, and infrastructure. In this work, we analyzed the factors affecting the probability of windthrow at stand level (i.e. tree- and stand characteristics) in southern Sweden. We selected a sub-sample (1721 plots) of existing plots from the Swedish National Forest Inventory (inventoried in 2003 and 2004). To assess whether these plots had suffered damage or not, aerial photographs were taken in summer 2005. In order to analyze the effects of measured characteristics on damage, field data for each sub-sample plot were merged with the corresponding result of the aerial photo interpretation. We found that the plots damaged were typically well stocked mature stands, dominated by Norway spruce (Picea abies (L.) Karst.), and often also recently thinned. Probability of damage increased with increase in stand height. In mixed stands, decrease of proportion of Norway spruce decreased the probability of damage. An admixture of deciduous trees, leafless in this winter storm, showed larger effect in this sense than that of Scots pine. [Copyright &y& Elsevier]

Research indicates that natural resources managed in common, resembling traditional commons such as the Swedish forest commons, could be a type of regime with the potential to stimulate successfully sustainable use conditions. This is supported by findings regarding the characteristics of Swedish forest commons, their claimed concern for the environment and relatively high proportion of old forest in two out of three regions. Swedish environmental policy is directed towards environmental quality objectives and the Sustainable Forests objective states, among other things, that biological diversity must be maintained and enhanced. Swedish National Forest Inventory data for the period 2003-2006 were used to analyse differences between forest commons in northern Sweden and other ownership categories regarding the proportion of forestland with a large deciduous element, the proportion of forest older than 80 years with a large (> 25%) deciduous element, the volume of dead wood and the proportion of forest older than 140 years, parameters corresponding to the interim targets for enhanced biological diversity. The results show no consistent differences in indicator variables between the forest commons and other ownership categories, signifying that forests managed in common have been conducted in ways promoting biodiversity more effectively than in other ownership categories. Further studies of different ownership categories regarding driving forces and forest status are warranted. [ABSTRACT FROM AUTHOR]

Abstract: The effectiveness of different conservation policies is debated, but the policies are rarely evaluated quantitatively. A voluntary or ‘soft’ policy based mainly on education provides information about ecosystems and effects of land use, to encourage conservation action. Swedish forestry relies mainly on soft policy, with substantial resources for education and advice to more than 200,000 forest owners, while legal regulation is weak. Increased retention of broadleaved trees at clear-cutting, with environmental benefits in the conifer-dominated forestry, is important in the policy. We used the Swedish National Forest Inventory to analyse this policy for young forests in southern Sweden. Between 1983–1987 and 1998–2002 the policy had no positive effect on saplings (1.3m tall to 4.9cm dbh) of birch, oak, beech and other species that mostly decreased in density, due to planting of conifers and browsing by ungulates. However, broadleaved conservation trees (≥15cm dbh) increased in density, e.g. to about one oak and six birches per ha in young coniferous forest in 1998–2002. The relative increase in density was higher for large (≥20cm dbh) than for small trees (15–20cm dbh). The density of conservation trees was higher on forestland of high than of low productivity. Thus, the soft conservation policy did not influence regeneration of saplings in this type of forestry system, but large broadleaved trees were increasingly saved at ‘clear-cuttings’. Advice and educational programmes probably contributed to this result. A continued increase in conservation trees at harvest may require economical support to forest owners. [Copyright &y& Elsevier]

Question: Detecting species presence in vegetation and making visual assessment of abundances involve a certain amount of skill, and therefore subjectivity. We evaluated the magnitude of the error in data, and its consequences for evaluating temporal trends. Location: Swedish forest vegetation. Methods: Vegetation data were collected independently by two observers in 342 permanent 100-m² plots in mature boreal forests. Each plot was visited by one observer from a group of 36 and one of two quality assessment observers. The cover class of 29 taxa was recorded, and presence/absence for an additional 50. Results: Overall, one third of each occurrence was missed by one of the two observers, but with large differences among species. There were more missed occurrences at low abundances. Species occurring at low abundance when present tended to be frequently overlooked. Variance component analyses indicated that cover data on 5 of 17 species had a significant observer bias. Observer-explained variance was < 10% in 15 of 17 species. Conclusion: The substantial number of missed occurrences suggests poor power in detecting changes based on presence/absence data. The magnitude of observer bias in cover estimates was relatively small, compared with random error, and therefore potentially analytically tractable. Data in this monitoring system could be improved by a more structured working model during field work. [ABSTRACT FROM AUTHOR]

Abstract: Forests and forestry in Sweden are dominated by conifers. Silviculture using mixed or broadleaved stands is often recommended, but the degree to which broadleaves regenerate naturally needs to be clarified. The Swedish National Forest Inventory is here used for a region-wide study of broadleaved saplings (1.3m tall to 4.9cmdbh) regenerated naturally. For 12 species (taxa) in young forests (&#60;7m tall) and high forests (≥7m), sapling densities were related to seven forest types and three productivity classes. Birch had highest densities in all but two broadleaved forest types. Birch, oak, rowan and sallow had 70–85% of their total sapling populations in conifer-dominated forest types, indicating good potential for mixed stands. Beech, lime, hornbeam, ash and elm were mostly restricted to ‘noble’ (hardwood) forests. The regeneration success (saplings per mature tree) for birch, rowan and oak was highest in conifer-dominated forest; beech was about equally successful in conifer-dominated and broadleaved forests, and ash was very successful in broadleaved forest. Oak regeneration may be problematical in broadleaved forests, but we suggest this is not the case in conifer-dominated forests (where oaks have rarely been studied). Sapling densities of the species in the forest types were not consistently correlated with productivity, but birch and aspen generally regenerated strongest at intermediate and at high productivity, respectively. In noble forests, oak, ash and elm regenerated strongest at low productivity. The role of asexual regeneration (sprouting) remains to clarify. Our results suggest that lime, elm, ash and some other trees currently are limited mainly by poor dispersal, rather than habitat availability. The results are promising for various forms of mixed-species forestry that does not require planting (or little planting) and that would be beneficial for nature conservation. [Copyright &y& Elsevier]

A new system is presented for predicting tree mortality, in order to improve Swedish long-term forest planning. A three-step approach was used, which consists of (I) estimating the probability of mortality on a sample plot; (II) quantifying the mortality in terms of proportion of basal area; and (III) distributing the mortality among individual trees. The system predicts the mortality for 5 yr periods. Data from permanent sample plots of the Swedish National Forest Inventory were used. Independent variables used for steps I and II were specific to site, stand and plot characteristics. In the step III models, which were tree-species specific, competition indices were also included. Logistic regression was used for steps I and III models, while linear regression was used for the step II models. A fair performance of the functions was observed, although mortality is a highly stochastic process. In applications, random simulation in all steps can mimic this. [ABSTRACT FROM AUTHOR]

Human activities have exerted a powerful influence on the biogeochemical cycles of nitrogen (N) and carbon (C) and drive changes that can be a challenge to predict given the influence of multiple environmental stressors. This study focused on understanding how land management and climate change have together influenced terrestrial N storage and watershed inorganic N export across boreal and sub-arctic landscapes in northern Sweden. Using long-term discharge and nutrient concentration data that have been collected continuously for over three decades, we calculated the hydrologic inorganic N export from nine watersheds in this region. We found a consistent decline in inorganic N export from 1985 to 2011 over the entire region from both small and large watersheds, despite the absence of any long-term trend in river discharge during this period. The steepest declines in inorganic N export were observed during the growing season, consistent with the hypothesis that observed changes are biologically mediated and are not the result of changes in long-term hydrology. Concurrent with the decrease in inorganic N export, we report sustained increases in terrestrial N accumulation in forest biomass and soils across northern Sweden. Given the close communication of nutrient and energy stores between plants, soils, and waters, our results indicate a regional tightening of the N cycle in an already N-limited environment as a result of changes in forest management and climate-mediated growth increases. Our results are consistent with declining inorganic N efflux previously reported from small headwater streams in other ecosystems and shed new light on the mechanisms controlling these patterns by identifying corresponding shifts in the terrestrial N balance, which have been altered by a combination of management activities and climate change.