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Publications

NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.

2025

Abstract

Intensification of forest management is seen as one important measure to increase carbon sequestration and contribute to balance CO2 emissions and mitigate climate change. Potential measures for forest management intensification include increasing the percentage of the area that is actively reforested after felling, planting at higher densities and with genetically improved material, nitrogen fertilization, and pre-commercial thinning. Here we assessed the mitigation potential of these practices in Norwegian forests from 2018 until the end of the 21st century. As a result, when these management practices were intensified, separately and simultaneously, carbon sequestration over the 80-year simulation period was larger than under current practices. Pre-commercial thinning gave the largest additional 80-year carbon dioxide removal increment and fertilization the smallest. The largest accumulated carbon dioxide removal potential occurred when intensifying all the proposed measures in one scenario and was estimated to be around 329.9 Tg CO2 by the end of the century, corresponding to offset more than six times Norway's total GHG emissions in 2022. If the intensification of these practices is considered separately, our results suggested that pre-commercial thinning and active reforestation after felling, in that order, should be prioritized as climate change mitigation measures, followed by genetic improvement, planting density and fertilization.

2024

Abstract

Forests, especially in the northern latitudes, are vulnerable ecosystems to climate change, and tree-ring data offer insights into growth-climate relationships as an important effect. Using the National Forest Inventory plot network, we analysed these correlations for the two dominant conifer species in Norway – Norway spruce and Scots pine – for the 1960–2020 period. For both species, the June climate was an important driver of radial growth during this period. Countrywide, the climate-growth correlations divided the Norwegian forests into spatial clusters following a broad shift from temperature- to water-sensitivity of growth with latitude and altitude. The clusters were delineated by a mean 1960–2020 June temperature of ca. 12°C for Norway spruce and Scots pine. The annual mean growing season and July temperatures – but not June temperature – has increased by 1.0 °C between the 1960–1990 and 1990–2020 periods, with a slight increase in precipitation. Despite this warming and wetting trend, the long-term growth-climate relationship has remained relatively stable between 1960 and 1990 and 1990–2020 for both species. The threshold between temperature and water-sensitive growth has not changed in the last two 31-year periods, following the stability of the June temperature compared with other months during the growing season. These findings highlight geographically coherent regions in Norway, segregating between temperature- and water-sensitive radial growth for the two major conifer species, temporally stable in the long-term for the 1960–2020 period studied.

Abstract

Forest restoration and improved forest management are seen as options to enhance terrestrial carbon dioxide removal in many regions, yet concerns surrounding their potentially adverse surface albedo impacts exist, particularly in high latitude and altitude regions. Such concerns are often based on generalized conclusions rooted in analyses carried out over broad spatial extents at coarse resolutions. The impacts of surface albedo change are highly sensitive to local environmental factors governing both the surface albedo and solar radiation budgets, and many previous assessments either do not sufficiently deal with such sensitivities or do not qualify the conditions under which they are relevant. Using the country of Norway with its diverse gradients in topography and climate as an ideal case study region, we seek clarity to the question of whether surface albedo is relevant to consider in forestry planning, and if so, what are the important factors determining it. We find that the adverse impact of a forest's albedo outweighs its carbon cycle benefit on only ∼4% of Norway's total forested area, reducing to <∼1% when future climate changes are considered. Our findings challenge the common perception that surface albedo concerns are highly relevant to forestry planning at high latitudes and emphasize the importance of carrying out albedo impact assessments at spatial scales aligning with those of local forestry planning.

Abstract

Forest management planning often relies on Airborne Laser Scanning (ALS)-based Forest Management Inventories (FMIs) for sustainable and efficient decision-making. Employing the area-based (ABA) approach, these inventories estimate forest characteristics for grid cell areas (pixels), which are then usually summarized at the stand level. Using the ALS-based high-resolution Norwegian Forest Resource Maps (16 ​m ​× ​16 ​m pixel resolution) alongside with stand-level growth and yield models, this study explores the impact of three levels of pixel aggregation (stand-level, stand-level with species strata, and pixel-level) on projected stand development. The results indicate significant differences in the projected outputs based on the aggregation level. Notably, the most substantial difference in estimated volume occurred between stand-level and pixel-level aggregation, ranging from −301 to +253 ​m3⋅ha−1 for single stands. The differences were, on average, higher for broadleaves than for spruce and pine dominated stands, and for mixed stands and stands with higher variability than for pure and homogenous stands. In conclusion, this research underscores the critical role of input data resolution in forest planning and management, emphasizing the need for improved data collection practices to ensure sustainable forest management.

Abstract

There is currently no quality sorting of harvested hardwood timber in Norway on a national scale. Medium- and high-quality logs including those from birch (Betula pubescens Ehrh., B. pendula Roth) are thus not utilized according to their potential monetary value. Increased domestic utilization of quality birch timber requires that the quality of harvested logs be properly assessed for potential end uses. A preferred sorting procedure would use visually detectable external log defects to grade roundwood timber. Knots are an important feature of inner log quality. Thus, the aim of this study was to evaluate whether correlations between branch scar size and knot features could be found in Norwegian birch. Using 168 knots from seven unpruned birch trees, external bark attributes often showed strong correlations with internal wood quality. Both length of the mustache and length of the seal performed well as predictors of stem radius at the time of knot occlusion. The presence of a broken off branch stub as part of an occluded knot significantly increased the knot-effected stem radius, proving that the practice of removing branches and branch stubs along the lower trunk is a crucial measure if quality timber production is the primary management goal.

Abstract

Hurdal (NO-Hur) is a recently labelled ICOS class 2 station in Southeast Norway. It represents a typical southern boreal forest of medium productivity, dominated by old Norway spruce (average tree height: 25 m, ages: up to 100 years) with some pine and broadleaved trees. The eddy covariance technique is used to measure CO2 fluxes on a 42 m tower since 2021 . The measurements have an average footprint area of approximately 63 ha. In 2023, the region experienced an unusual dry spring and then an extraordinary flood in August. Both events showed significant impact on the Net Ecosystem Exchange (NEE) and heat fluxes. The station is also equipped with automatic dendrometers and sap flow devices on the dominant spruce trees, allowing us to investigate the impact of these events at the individual tree scale. We will present tree growth and transpiration flux at different temporal scales (from sub-daily to seasonal), and relate these single tree observations with environmental variables, ecosystem-level NEE and evapotranspiration using phase synchronization analysis. These observational data will yield insights into carbon and water processes of a boreal forest at different scales in response to multiple disturbances.