Jonas Fridman

Disentangling biodiversity and climatic determinants of wood production.

Background Despite empirical support for an increase in ecosystem productivity with species diversity in synthetic systems, there is ample evidence that this relationship is dependent on environmental characteristics, especially in structurally more complex natural systems. Empirical support for this relationship in forests is urgently needed, as these ecosystems play an important role in carbon sequestration. Methodology/Principal Findings We tested whether tree wood production is positively related to tree species richness while controlling for climatic factors, by analyzing 55265 forest inventory plots in 11 forest types across five European countries. On average, wood production was 24% higher in mixed than in monospecific forests. Taken alone, wood production was enhanced with increasing tree species richness in almost all forest types. In some forests, wood production was also greater with increasing numbers of tree types. Structural Equation Modeling indicated that the increase in wood production with tree species richness was largely mediated by a positive association between stand basal area and tree species richness. Mean annual temperature and mean annual precipitation affected wood production and species richness directly. However, the direction and magnitude of the influence of climatic variables on wood production and species richness was not consistent, and vary dependent on forest type. Conclusions Our analysis is the first to find a local scale positive relationship between tree species richness and tree wood production occurring across a continent. Our results strongly support incorporating the role of biodiversity in management and policy plans for forest carbon sequestration.

Modelling probability of snow and wind damage in Scots pine stands using tree characteristics

Abstract Predictions of damage risk from snow and wind at sites using tree characteristics of Scots pine ( Pinus sylvestris L.), were made using a subset of data from permanent sample plots within the Swedish National Forest Inventory (NFI). The plots were sampled twice at five-year intervals between 1983 and 1992. A logistic risk assessment model was developed using data originating from 286 plots, dominated by Scots pine (> 65% of basal area), within one county situated in the boreal zone in northern Sweden (Vasterbotten). The model was evaluated with NFI-data from two other counties, one adjacent to Vasterbotten (Vastermorrland, 99 plots), which is also in the boreal zone, and one (Kalmar, 138 plots) in the hemi-boreal zone in southern Sweden. In each plot, measurements at first inventory of tree characteristics for the largest undamaged sample tree, and measurements at second inventory of damage from snow and wind on all sample trees were used to develop a logistic model that predicts the damage probability for each site. The best predictors were upper diameter ( ud , diameter at 3 or 5 m) and the ratio of height/diameter at breast height ( rhd ). According to the model calculations, the overall damage probability never exceeded 0.26 for any of the sample plots used for model development. At a given ud the probability of damage is higher for a site with trees of low rhd . The fit of the model was better for the adjacent Vasternorrland county than for the southern county, Kalmar. This inferior predictability was explained by differences in tree characteristics between Kalmar and the other counties. The results show that it is possible to predict damage from snow and wind at a site by using only single tree characteristics.

A Three-step Approach for Modelling Tree Mortality in Swedish Forests

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.

Conservation of Forest in Sweden: a strategic ecological analysis

Policies for future conservation of forests must be preceded by an evaluation of the present reserves. Using data from the Swedish National Forest Inventory, this study analyses Swedish reserves, i.e. national parks, nature reserves and forest service reserves, in terms of proportion of forest, stand age, site quality, tree species composition and tree volumes. The results show that in Sweden, the proportion of productive forest within reserves is 20% compared to 60% of the non-reserve land area, and that the volume of dead trees is greater in reserves. In general the distribution of forests within reserves is skewed towards old, low-productivity Norway spruce forests in Northwest Sweden. This allocation may not meet the demands for protection of the habitats of endangered species.

Modelling probability of snow and wind damage using tree, stand, and site characteristics from Pinus sylvestris sample plots

The risk of damage on trees from snow and wind was modelled using tree, stand, and site characteristics from 286 permanent Scots pine (Pinus sylvestris L.) sample plots within the Swedish National Forest Inventory. Three logistic risk assessment models were developed for the county of Vasterbotten in the boreal zone of Sweden. The best model, using tree, stand, and site variables, correctly classified 81.1% of the undamaged and 81.8% of the damaged plots. The model over‐predicted the proportion of damaged plots (21.3%), compared to the observed proportion of 3.8%. When evaluating the models using temporary plots from Vasterbotten, the model using tree, stand, and site variables showed the best overall predictability. When applied in southern Sweden, the models developed for Vasterbotten showed poor predictability. The study shows possibilities for correctly classifying the overall susceptibility to damage from snow and wind if the models are used within their limits.

Long‐term declines in stream and river inorganic nitrogen (N) export correspond to forest change

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.

Forest management and forest state in southern Sweden before and after the impact of storm Gudrun in the winter of 2005

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 m3 after 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 m3 in 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.

Comparison of methods used in European National Forest Inventories for the estimation of volume increment: towards harmonisation

Key messageThe increment estimation methods of European NFIs were explored by means of 12 essential NFI features. The results indicate various differences among NFIs within the commonly acknowledged methodological frame. The perspectives for harmonisation at the European level are promising.ContextThe estimation of increment is implemented differently in European National Forest Inventories (NFIs) due to different historical origins of NFIs and sampling designs and field assessments accommodated to country-specific conditions. The aspired harmonisation of increment estimation requires a comparison and an analysis of NFI methods.AimsThe objective was to investigate the differences in volume increment estimation methods used in European NFIs. The conducted work shall set a basis for harmonisation at the European level which is needed to improve information on forest resources for various strategic processes.MethodsA comprehensive enquiry was conducted during Cost Action FP1001 to explore the methods of increment estimation of 29 European NFIs. The enquiry built upon the preceding Cost Action E43 and was complemented by an analysis of literature to demonstrate the methodological backgrounds.ResultsThe comparison of methods revealed differences concerning the NFI features such as sampling grids, periodicity of assessments, permanent and temporary plots, use of remote sensing, sample tree selection, components of forest growth, forest area changes, sampling thresholds, field measurements, drain assessment, involved models and tree parts included in estimates.ConclusionIncrement estimation methods differ considerably among European NFIs. Their harmonisation introduces new issues into the harmonisation process. Recent accomplishments and the increased use of sample-based inventories in Europe make perspectives for harmonised reporting of increment estimation promising.

Biological diversity indicators: A comparison of Swedish forest commons and other forest ownership categories

Abstract 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.

Monitoring of Forest Biodiversity from Forest Resource Inventory Data

Forest biodiversity has become a new concern for society. It has introduced new regulations and new ways of thinking in areas of forest use and planning. In Sweden the Forestry Act of 1993 states that timber production and maintenance of biodiversity are objectives of equal dignity. This results in a need for monitoring the maintenance of biodiversity in order to know if the policy intentions are followed. The problem of maintenance of biodiversity can be looked at from different scales, such as species, ecosystem, landscape, regional and national.