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• Asplund, Ulrika Jansson; Karlsen, Damian Petkovic; Brysting, Anne Krag; Halvorsen, Rune; Kauserud, Håvard & Kjønaas, Janne [Vis alle 7 forfattere av denne artikkelen] (2026). Long-term effects of clear-cutting on understory plant communities in boreal forests. Forest Ecology and Management. ISSN 0378-1127. 613. doi: 10.1016/j.foreco.2026.123784. Fulltekst i vitenarkiv Vis sammendrag

  After five centuries of selective cutting in the boreal Fennoscandian forest there was a shift to stand replacing harvest (clear-cutting) in the 1940s. This shift altered light conditions experienced by the forest understory profoundly, from semi-open conditions to light regimes altering between very open in the recently clear-cut forest to very dense some decades later. In this study, we investigated the long-term effects of clear-cutting on vascular plants and bryophytes. Our study system consists of twelve pairs of mesic spruce forests in Southeastern Norway, with a previously clear-cut, but now mature stand and a near-natural forest within each pair. Vascular plant cover was almost twice as high in the near-natural than in the mature, previously clear-cut forest sites, despite similar standing volume and light availability. Overall, previous clear-cutting did not have long-term effects on species richness, but vascular plant species richness was more responsive to soil Ca, a key driver of plant community composition, in the near natural forests. Likewise, the community composition showed a stronger association with soil chemistry in near-natural forests, suggesting that management alters natural drivers of understory communities. The long-lasting effects of clear-cutting was distinct for understory cover and mainly driven by common species such as the keystone species Vaccinium myrtillus, which was substantially less abundant in previously clear-cut stands.

• Kjønaas, Janne; Clarke, Nicholas; Petrovičová, Lucia & Světlík, Jan (2025). Assessing carbon stocks, C stock changes, and sensitivity analyses of factors affecting estimated C stocks in six Norwegian forest soils. Scandinavian Journal of Forest Research. ISSN 0282-7581. 40(7-8), s. 321–356. doi: 10.1080/02827581.2025.2533379. Fulltekst i vitenarkiv Vis sammendrag

  We assessed soil organic carbon (SOC) stocks and changes across six upland forest sites with 13replicated plots, spanning bioclimatic regions from the boreonemoral to the northern borealzone. The sites included three ICP Forests Level II plots in older coniferous stands and threelong-term experiments focusing on thinning intensity, tree species effects (Norway spruce, Scotspine, silver birch), and mixtures of Norway spruce and downy birch, the latter two followingclear-cutting. Repeated soil surveys spanned 9–34 years. SOC stocks in the organic LFH horizonranged from 1.4 to 3.6 kg m−2, while total stocks down to 30 cm and 70–100 cm mineral soildepths ranged from 3.0 to 13.5 kg m−2 and 8.5 to 17.5 kg m−2, respectively. Annual SOC stockchanges in the LFH horizon ranged from −106 to 111 g m−2 yr−1, with significant changesobserved in five plots. Total SOC stock changes down to 15, 18 or 20 cm mineral soil depthranged from −77 to 154 g m−2 yr−1, with significant increases detected in two ICP level II plots.Sensitivity analyses supported these findings but highlighted inconsistencies in samplingmethods, hight spatial variability, and limited replicates, affecting estimates in the remaining 11plots.ARTICLE HISTORYReceived 31 March 2025Accepted 8 July 2025KEYWORDSBoreal forest; downy birch;Norway spruce; Scots pine;soil organic carbon; SOC;SOC stock changesIntroductionForest ecosystems are crucial biomes for carbon (C)storage, with boreal forests playing a significant role asa C sink (Pan et al. 2011; Watts et al. 2023). Globally,the soil organic carbon (SOC) pool contains more thanthree times as much C as the atmosphere (Schmidt etal. 2011). From a climate perspective, the importanceof SOC storage is tied to its overall size as well as itspotential as a long-term reservoir. Estimates of SOCstocks in boreal upland forests suggest 3–4 times moreC relative to the aboveground tree biomass (Scharle-mann et al. 2014; Bradshaw and Warkentin 2015). Thebiological stability of SOC is mediated by a broad setof environmental drivers, notably temperature and soilmoisture content (Soucémarianadin et al. 2018).Additionally, microbial communities play an importantrole in both decomposition and accumulation of SOC(Lindahl et al. 2021; Gundale et al. 2024), processesthat are further influenced by forest management prac-tices (Mayer et al. 2020; Jörgensen et al. 2022) and treespecies (Mundra et al. 2022, 2024). The effect of treespecies on SOC stocks may primarily influence the distri-bution of SOC within the soil profile rather than the totalSOC stock (Vesterdal et al. 2013; Kjønaas et al. 2021). Thisdistribution, however, affects the stability of SOC and itsvulnerability to decomposition, consequently impactingthe CO2 flux from the soil (James and Harrison 2016;Cotrufo et al. 2019; Georgiou et al. 2024).Estimated C allocation in Norwegian forests is approxi-mately 21% in vegetation and 79% in soil (Grønlund etal. 2010). SOC stocks in Norwegian forest soils are con-sidered higher compared to those of Sweden andFinland (Olsson et al. 2009; Rantakari et al. 2012; Strandet al. 2016). This disparity may partly stem from varyinginventory methods. However, differences in precipitationand temperature gradients account for approximately68% of the variability in SOC stocks across Nordic forests(Callesen et al. 2003), suggesting that climate factors alsoplay a significant role. On a European scale, coniferousforest soils represent one of the largest and most vulner-able SOC stocks (Lugato et al. 2021). The size and stabilityof the SOC stock may determine the magnitude of© 2025 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis GroupThis is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use,distribution, and reproduction in any medium, provided the original work is properly cited. The terms on which this article has been published allow the posting of the AcceptedManuscript in a repository by the author(s) or with their consent.CONTACT O. Janne Kjønaas janne.kjonaas@nibio.noSupplemental data for this article can be accessed online at https://doi.org/10.1080/02827581.2025.2533379.SCANDINAVIAN JOURNAL OF FOREST RESEARCH2025, VOL. 40, NOS. 7–8, 321–356https://doi.org/10.1080/02827581.2025.2533379

• Madsen, Rieke Lo; Nybakken, Line; Kjønaas, O. Janne; Kauserud, Håvard & Asplund, Johan (2025). Decomposition of plant, fungal and tea litter in Picea abies forests with and without a history of clear-cutting. Agriculture, Ecosystems & Environment. Applied Soil Ecology. ISSN 0929-1393. 215. doi: 10.1016/j.apsoil.2025.106485. Fulltekst i vitenarkiv Vis sammendrag

  Litter decomposition is coupled to carbon (C) sequestration through C release to the atmosphere, C transformation and nutrient release to the soil. We investigated if clear-cutting has long-term effects on this vital ecological process and consequently on C dynamics in boreal forests using twelve pairs of previously clear-cut and near-natural forests. Three litterbag experiments were conducted using (I) standardised spruce and bilberry litter, (II) melanised and non-melanised fungal necromass and (III) rooibos and green tea. We found weak and inconsistent effects of harvesting history, that did not depend on litter quality or mesofauna exclusion. Litter quality was more important in explaining net mass remaining for fungal necromass than for aboveground plant litter. Mesofauna exclusion had only marginal effects on initial litter decomposition. Results obtained with the highly standardised Tea Bag Index were not readily comparable to those of the plant litter or fungal necromass and we therefore question its use in this regional context. Further, we show that net mass or C remaining in the litterbags do not correlate consistently with in situ soil respiration. This finding is discussed in relation to previous measurements of soil C fluxes from the same system. In conclusion, we suggest that potential disturbances to the physical environment or the capacity of the decomposer community to facilitate litter decomposition are no longer clearly evident when clear-cut stands approach maturity.

• Johannesson, Carl-Fredrik; Ilvesniemi, H.; Kjønaas, O. Janne; Larsen, K.S.; Lehtonen, A. & Nordén, Jenni [Vis alle 12 forfattere av denne artikkelen] (2025). Decadal decline in forest floor soil organic carbon after clear-cutting in Nordic and Canadian forests. Forest Ecology and Management. ISSN 0378-1127. 586. doi: 10.1016/j.foreco.2025.122668. Fulltekst i vitenarkiv Vis sammendrag

  Nordic and Canadian forests store substantial amounts of carbon (C) and are largely managed in a silvicultural system with clear-cut harvest. Previous meta-analyses of harvesting effects on soil C have shown short- to long-term declines after harvest, but effects of clear-cutting on boreal and northern temperate forest soil C stocks remain unresolved. We harmonized National Forest Soil Inventory (NFSI) data from Sweden, Denmark, Finland, Norway and Canada to examine soil C stocks up to 53 years following clear-cut harvest using a space-for-time approach. We analyzed forest floor and mineral soil C stocks in coniferous and deciduous/mixed forests. Coniferous forest floor C stocks decreased for ∼30 years after clear-cutting: when at its lowest stock level, Picea and Pinus forest floor C stocks had decreased by 23 % and 14 % relative to initial stock levels, respectively. Picea forest floor C stocks then remained close to its lowest levels until 53 years after clear-cutting, while for Pinus-dominated forests they increased again and recovered to the pre-harvest level 48 years after clear-cutting. No C stock changes were detected in the 0–10 cm or 10–20 cm mineral soil layers, while a small increase in 55–65 cm mineral soil was detected in Podzol soils. Data was too limited to detect statistical signals of clear-cutting for deciduous/mixed forests. Our results shows that clear-cut harvest has substantial and long-lasting effects on northern temperate and boreal forest soil C storage, and that combining data from several NFSIs can help elucidate forest management effects on soil C storage. Soil organic carbonForest harvestClear-cuttingBorealTemperateNational forest inventoryNational forest soil inventory

• Hagenbo, Andreas; Dalsgaard, Lise; Hauglin, Marius; Eisner, Stephanie; Strand, Line Tau & Kjønaas, O. Janne (2025). Spatial predictive modeling of soil organic carbon stocks in Norwegian forests. Science of the Total Environment. ISSN 0048-9697. 980. doi: 10.1016/j.scitotenv.2025.179451. Fulltekst i vitenarkiv Vis sammendrag

  Boreal forest soils are a critical terrestrial carbon (C) reservoir, with soil organic carbon (SOC) stocks playing a key role in global C cycling. In this study, we generated high-resolution (16 m) spatial predictions of SOC stocks in Norwegian forests for three depth intervals: (1) soil surface down to 100 cm depth, (2) forest floor (LFH layer), and (3) 0–30 cm into the mineral soil. Our predictions were based on legacy soil data collected between 1988 and 1992 from a subset (n = 1014) of National Forest Inventory plots. We used boosted regression tree models to generate SOC estimates, incorporating environmental predictors such as land cover, site moisture, climate, and remote sensing data. Based on the resulting maps, we estimate total SOC stocks of 1.57–1.87 Pg C down to 100 cm, with 0.55–0.66 Pg C stored in the LFH layer and 0.68–0.80 Pg C in the upper mineral soil. These correspond to average SOC densities of 15.3, 5.4, and 6.6 kg C m−2, respectively. We compared the predictive performance of these models with another set, supplemented by soil chemistry variables. These models showed higher predictive performance (R2 = 0.65–0.71) than those used for mapping (R2 = 0.44–0.58), suggesting that the mapping models did not fully capture environmental variability influencing SOC stock distributions. Within the spatial predictive models, Sentinel-2 Normalized Difference Vegetation Index, depth to water table, and slope contributed strongly, while soil nitrogen and manganese concentrations had major roles in models incorporating soil chemistry. Prediction uncertainties were related to soil depth, soil types, and geographical regions, and we compared the spatial prediction against external SOC data. The generated maps of this offer a valuable starting point for identifying forest areas in Norway where SOC may be vulnerable to climate warming and management-related disturbances, with implications for soil CO2 emissions.

• Lunde, Lisa Fagerli; Birkemoe, Tone; Sverdrup-Thygeson, Anne; Asplund, Johan; Halvorsen, Rune & Kjønaas, O. Janne [Vis alle 11 forfattere av denne artikkelen] (2025). Towards repeated clear-cutting of boreal forests – a tipping point for biodiversity? Biological Reviews. ISSN 1464-7931. 100(3), s. 1181–1205. doi: 10.1111/brv.13180. Fulltekst i vitenarkiv Vis sammendrag

  Boreal forests are important carbon sinks and host a diverse array of species that provide important ecosystem functions. Boreal forests have a long history of intensive forestry, in which even-aged management with clear-cutting has been the dominant harvesting practice for the past 50–80 years. As a second cycle of clear-cutting is emerging, there is an urgent need to examine the effects of repeated clear-cutting events on biodiversity. Clear-cutting has led to reduced numbers of old and large trees, decreased volumes of dead wood of varied decay stages and diameters, and altered physical and chemical compositions of soils. The old-growth boreal forest has been fragmented and considerably reduced. Here, we review short- and long-term (≥50 years) effects of clear-cutting on boreal forest biodiversity in four key substrates: living trees, dead wood, ground and soil. We then assess landscape-level changes (habitat fragmentation and edge effects) on this biodiversity. There is evidence for long-term community changes after clear-cutting for several taxa: epiphytic lichens; saproxylic fungi, bryophytes and insects; epigeic bryophytes; and soil snails, bacteria, and ectomycorrhizal fungi. Long-term declines in species richness were found for saproxylic fungi, bryophytes and true flies. However, for the majority of taxa, long-term effects of clear-cutting are not well understood. On the landscape level, reduced connectivity to old-growth forests has negative effects on several species of fungi, lichens, bryophytes and insects, notably among Red-Listed species. Furthermore, altered microclimate near clear-cut edges negatively affects epiphytic lichens and epigeic arthropods, implying complex effects of habitat fragmentation. Repeated cycles of clear-cutting might pose even stronger pressures on boreal forest biodiversity due to continued fragmentation of old-growth forests and accumulation of extinction debts. Examining the broad effects of forestry on biodiversity across the boreal biome is crucial: (i) to increase our knowledge of long-term and landscape-level effects of former clear-cutting; and (ii) to gain a better understanding of how forestry will affect biodiversity and, subsequently, ecosystem functioning, with repeated cycles of clear-cutting.

• Madsen, Rieke Lo; Asplund, Johan; Nybakken, Line; Biong, Rebecca & Kjønaas, O. Janne (2025). Harvesting history affects soil respiration and litterfall but not overall carbon balance in boreal Norway spruce forests. Forest Ecology and Management. ISSN 0378-1127. 578, s. 1–18. doi: 10.1016/j.foreco.2024.122485. Fulltekst i vitenarkiv Vis sammendrag

  Understanding long-term effects of clear-cutting on current soil carbon (C) fluxes in boreal forests is important in the perspective of global C cycling and future forest management decisions. We studied twelve pairs of forest stands in South-Eastern Norway, each comprised of one previously clear-cut stand and one near-natural stand with similar macroclimate, topography and soil properties. We measured aboveground tree litterfall continuously during two consecutive years and soil respiration fluxes monthly during the snow-free period of one year. Ground vegetation litterfall was estimated from destructive biomass sampling. The previously clear-cut stands had on average 12 % higher annual soil respiration rates, 20 % greater tree litterfall, and tended to have greater total aboveground litterfall (12 %), while the near-natural stands had greater litterfall from ground vegetation (45 %). Litterfall from ground vegetation was strongly linked with below-canopy light transmission, but the contribution of this flux to the total aboveground litterfall was minor. Soil respiration rates were related to microclimate, nitrogen concentration in aboveground tree litter and tree basal area. Though, only basal area could be linked to management type differences in soil respiration, that likely has additional unidentified drivers. We found similar temperature sensitivities of soil respiration in the two management types. We emphasise that age of the dominating trees is an integrated part of the differences between these two types of forest stands. Jointly, our results suggest limited differences in the current net soil C balance of near-natural and previously clear-cut stands.

• Mundra, Sunil; Loganathachetti, Dinesh Sanka; Kauserud, Håvard; Fiore-Donno, Anna Maria; Økland, Tonje & Nordbakken, Jørn-Frode [Vis alle 7 forfattere av denne artikkelen] (2024). Tree species replacement from birch to spruce affects eukaryome in boreal forest soil. European journal of soil biology. ISSN 1164-5563. 120, s. 1–4. doi: 10.1016/j.ejsobi.2023.103593. Fulltekst i vitenarkiv Vis sammendrag

  Large-scale replacements of native birch with spruce have been carried out in Western Norway for economic reasons. This tree species shift potentially affects biotic components such as the eucaryome, consisting of microscopic animals (Metazoa), protists and fungi, which are key players in the functioning of forest ecosystem. The impact on the belowground eukaryome and its interactions with vegetation and soil properties is not well assessed. We examined the impact of replacing native birch with Norway spruce plantations on the eukaryome of the boreal forest floor in Western Norway using 18S rDNA metabarcoding. The tree species shift from birch to spruce had significant impacts on the eukaryome at both taxonomic (Metazoa) and functional categories (phagotrophs, phototrophs, parasites and osmotrophs). The distinct differences in eukaryome communities were related to changes in understorey vegetation biomass and soil chemistry following the tree species shift. This had a negative effect on eukaryome richness, particularly affecting phagotrophs and parasites, while the opposite was observed for osmotroph richness. Our results indicated that the spruce plantations altered the eukaryome communities and their food-web patterns compared to what was found in the native birch forest soil. This information should be taken into consideration in forest management planning.

• Asplund, Johan; Nordén, Jenni; Kjønaas, O. Janne; Madsen, Rieke Lo; Lunde, Lisa Fagerli & Birkemoe, Tone [Vis alle 18 forfattere av denne artikkelen] (2024). Long term effects of forest management on forest structure and dead wood in mature boreal forests. Forest Ecology and Management. ISSN 0378-1127. 572. doi: 10.1016/j.foreco.2024.122315. Fulltekst i vitenarkiv Vis sammendrag

  The history of forestry in Fennoscandia spans five centuries, with clear-cutting being the dominant practice since the mid-20th century. This has led to a significant transformation of the forest landscape. In this study we investigated long-term effects of clear-cutting on forest structure and dead wood volumes. We established twelve pairs of spruce forest sites in southeastern Norway, each pair constituting of a mature, previously clear-cut stand and its near-natural counterpart with similar edaphic factors. The near-natural stands had 2.8 times higher volumes of dead wood and a larger proportion of dead wood in late stages of decay. The near-natural stands had on average 36.8 ± 9.1 m3 ha− 1 of downed dead wood and 24.1 ± 6.2 m3 ha− 1 of standing dead wood. Corresponding numbers for the previously clear-cut stands were 10.2 ± 2.8 m3 ha− 1 and 11.9 ± 3.7 m3 ha− 1 . Forests with lower volumes of dead wood often also had lower connectivity of old spruce forests, which potentially have further negative effects on biodiversity. Furthermore, near-natural stands displayed greater tree size heterogeneity, resulting in a wider variation in light conditions. While no difference was observed in living tree volume, we found only weak evidence for higher basal area in the previously clear-cut stands, which had a higher stem density with more slender stems and shorter crowns. Our findings suggest that managed forests do not develop structures typical of near-natural forests before they become mature for logging. We stress the importance of a thorough site selection for studies of management effects, as forest management history may be confounded with productivity and other edaphic factors. Experimental designs like ours are vital for testing how differences in structure and deadwood volumes, driven by forest management, translate into variations in biodiversity, carbon sequestration and ecosystem functioning in future studies Coarse woody debris Clear-cutting forestry Norway spruce Structural heterogeneity

• Callesen, Ingeborg; Palviainen, Marjo; Armolaitis, Kęstutis; Rasmussen, Charlotte & Kjønaas, O. Janne (2023). Soil texture analysis by laser diffraction and sedimentation and sieving–method and instrument comparison with a focus on Nordic and Baltic forest soils. Frontiers in Forests and Global Change. 6, s. 1–14. doi: 10.3389/ffgc.2023.1144845. Fulltekst i vitenarkiv Vis sammendrag

  Purpose: Laser diffraction (LD) for determination of particle size distribution (PSD) of the fine earth fraction appeared in the 1990s, partly substituting the Sieving and Sedimentation Method (SSM). Whereas previous comparison between the two methods predominantly encompasses agricultural soils, less attention has been given to forest soils, including pre-treatment requirements related to their highly variable contents of carbon and Alox+ Feox. In this small collaborative learning study we compared (1) national SSM results with one type/protocol of LD analysis (Coulter), (2) LD measurements performed on three different LD instruments / laboratories, and (3) the replication error for LD Coulter analysis of predominantly sandy and loamy forest soils. Methods: We used forest soil samples from Denmark, Norway and Lithuania and their respective national SSM protocols / results. LD analyses were performed on Malvern Mastersizer 2000, Sympatec HELOS version 1999, and Coulter LS230, located at University of Copenhagen, Aarhus University and Helsinki University, respectively. The protocols differed between laboratories, including the use of external ultrasonication prior to LD analysis. Results: The clay and silt fractions content (<20 μm) from the LD analysis were not comparable with SSM results, with differences ranging from −0.5 to 22.3 percentage points (pp) for clay. Preliminary results from loamy samples with spodic material suggested inconsistent effects of external ultrasonication to disperse aggregates. The comparison between the three LD instruments showed a range in the clay and silt fractions content of 1.9–5.3 and 6.2–8.1 pp, respectively. Differences may be related to the instruments, protocols, and content of a given particle size fraction. The replication error of the Coulter LD protocol was found to be <3 pp in sandy soils, but up to 10 pp in loamy soils. Conclusion: Differences in the clay fraction results partly affected the classification of soil types. The fast replication of the LD analysis enables more quality control of results. The pedological evaluation of non-silicate constituents and optional pre-treatment steps (e.g., soil organic matter or sesquioxides) remains the same for LD and SSM. For comparison of results, detailed descriptions of the analytical protocol including pre-treatments are needed irrespective of instrument and theoretical approach.

• Simonsen, Morten; Kjønaas, O. Janne & Aall, Carlo Leandro (2022). Substitution of fossil-energy intensive building materials by wood products – Does it matter? A case study from Western Norway. Journal of Cleaner Production. ISSN 0959-6526. 383. doi: 10.1016/j.jclepro.2022.134941. Fulltekst i vitenarkiv Vis sammendrag

  Forest management is an important tool for GHG mitigation by representing three carbon pools: living biomass, forest soil, and wood-based products. Additionally, increasing attention has been given to the potential for wood products to substitute fossil-intensive products as a climate mitigation strategy. The goal of this paper is to analyse the theoretical GHG effects of fully replacing four common non-wood products with wood-based products of ‘low’ and ‘high’ technology options that have a similar functionality: (1) Spruce particle board substituting polyurethane (PU) foam insulation board; (2) spruce cross-laminated timber beam (CLT) substituting steel beam; (3) birch energy wood substituting electric heating; and (4) birch plywood substituting plaster board. The analysis was based on forestry in Western Norway as a case study, where forests typically consist of naturally generated birch and expanding areas of planted Norway spruce. In this study we compare wood products derived from paired stands of Norway spruce and downy birch. The analysis showed that spruce gave a higher theoretical substitution effect relative to birch for the selected pairs of woody and non-woody products. CLT substituting steel beam gave the highest substitution effect, approximately 15% higher than particle board substituting PU foam board. The theoretical substitution effect in mass units of carbon per kg wood product for the two spruce wood products was approximately 17 times higher relative to substituting Norwegian hydro energy-based electric heating, whereas plywood substituting plaster board may in fact increase GHG emissions. As the gross emissions were relatively similar for the birch plywood and the spruce particle board, the major substitution effect was related to the avoided emission of the non-woody product rather than to the tree species per se. The paper concludes that the choice of product to be substituted was the key factor that determined the final substitution effects. Furthermore, the study showed that transportation was the single most important factor that affected the emissions between planting and delivery of the timber at production gate. The analysis enables informed decisions related to CO2-emissions at the various steps from tree planting to wood conversion, and underline the importance of informed decision related to the choice of substitution products.

• Mundra, Sunil; Kauserud, Håvard; Økland, Tonje; Nordbakken, Jørn-Frode; Ransedokken, Yngvild Eidissen & Kjønaas, O. Janne (2022). Shift in tree species changes the belowground biota of boreal forests. New Phytologist. ISSN 0028-646X. 234(6), s. 2073–2087. doi: 10.1111/nph.18109. Fulltekst i vitenarkiv Vis sammendrag

  The replacement of native birch with Norway spruce has been initiated in Norway to increase long-term carbon storage in forests. However, there is limited knowledge on the impacts that aboveground changes will have on the belowground microbiota. We examined which effects a tree species shift from birch to spruce stands has on belowground microbial communities, soil fungal biomass and relationships with vegetation biomass and soil organic carbon (SOC). Replacement of birch with spruce negatively influenced soil bacterial and fungal richness and strongly altered microbial community composition in the forest floor layer, most strikingly for fungi. Tree species-mediated variation in soil properties was a major factor explaining variation in bacterial communities. For fungi, both soil chemistry and understorey vegetation were important community structuring factors, particularly for ectomycorrhizal fungi. The relative abundance of ectomycorrhizal fungi and the ectomycorrhizal : saprotrophic fungal ratio were higher in spruce compared to birch stands, particularly in the deeper mineral soil layers, and vice versa for saprotrophs. The positive relationship between ergosterol (fungal biomass) and SOC stock in the forest floor layer suggests higher carbon sequestration potential in spruce forest soil, alternatively, that the larger carbon stock leads to an increase in soil fungal biomass.

• Kjønaas, O. Janne; Barcena, Teresa G.; Hylen, Gro; Nordbakken, Jørn-Frode & Økland, Tonje (2021). Boreal tree species change as a climate mitigation strategy: impact on ecosystem C and N stocks and soil nutrient levels. Ecosphere. 12(11). doi: 10.1002/ecs2.3826. Fulltekst i vitenarkiv Vis sammendrag

  To increase the annual uptake of CO2 as well as the long-term storage of carbon (C) in forests, the Norwegian government consider large-scale replacements of native, deciduous forests with faster-growing species like Norway spruce. To assess the effects of tree species change on ecosystem C and nitrogen (N) stocks and soil chemistry, we used a paired plot approach including stands of native downy birch and planted 45 – 60-year-old Norway spruce. The birch stands were used as reference for the assessment of differences following the tree species change. We found significantly higher C and N stocks in living tree biomass in the spruce stands, whereas no significant differences were found for dead wood. The cover of understory species groups, and the C and N stocks of the aboveground understory vegetation was significantly higher in the birch stands. The tree species change did not affect the soil organic carbon (SOC) stock down to 1 m soil depth; however, the significantly higher stock in the forest floor of the spruce stands suggested a re-distribution of SOC within the profile. There was a significant positive correlation between the SOC stock down to 30 cm soil depth and the total ecosystem C stock for the birch stands, and a negative correlation for the spruce stands. Significant effects of tree species change were found for C and N concentrations, C/N, exchangeable acidity, base saturation, and exchangeable Ca, K, Mg, Na, S, and Fe in the organic horizon or the upper mineral soil layer. The total ecosystem C stock ranged between 197 and 277 Mg ha-1 for the birch stands, and 297 and 387 Mg ha-1 for the spruce stands. The ecosystem C accumulation varied between 32 and 142 Mg ha-1 over the past 45-60 years, whereas the net ecosystem C capture was considerably lower and potentially negative. Our results suggest that the potential to meet the governments’ targets to increase C sequestration depend on the C debt incurred from the removed birch stands, the rotation length, and potentially also the susceptibility of the different stand types to future risk factors related to climate change.

• Clarke, Nicholas; Kiær, Lars Pødenphant; Kjønaas, O. Janne; Bárcena, Teresa G.; Vesterdal, Lars & Stupak, Inge [Vis alle 12 forfattere av denne artikkelen] (2021). Effects of intensive biomass harvesting on forest soils in the Nordic countries and the UK: A meta-analysis. Forest Ecology and Management. ISSN 0378-1127. 482. doi: 10.1016/j.foreco.2020.118877. Fulltekst i vitenarkiv Vis sammendrag

  The use of biomass from forest harvesting residues or stumps for bioenergy has been increasing in the northern European region in the last decade. The present analysis is a regional review from Nordic and UK coniferous forests, focusing on the effects of whole-tree harvesting (WTH) or whole-tree thinning (WTT) and of WTH followed by stump removal (WTH + S) on the forest floor and mineral soil, and includes a wider array of chemistry data than other existing meta-analyses. All intensified treaments led to significant decreases of soil organic carbon (SOC) stock and total N stock in the forest floor (FF), but relative responses compared with stem-only harvesting were less consistent in the topsoil (TS) and no effects were detected in the subsoil (SS). Exchangeable P was reduced in the FF and TS both after WTT and WTH, but significant changes in exchangeable Ca, K, Mg and Zn depended on soil layer and treatment. WTH significantly lowered pH and base saturation (BS) in the FF, but without apparent changes in cation exchange capacity (CEC). The only significant WTH-effects in the SS were reductions in CEC and BS. Spruce- and pine-dominated stands had comparable negative relative responses in the FF for most elements measured except Mg and for pH. Relative responses to intensified harvesting scaled positively with growing season temperature and precipitation for most variables, most strongly in FF, less in the TS, but almost never in the SS, but were negative for P and Al. The greater reduction in FF and TS for soil organic carbon after intensive harvesting decreased with time and meta-regression models predicted an average duration of 20–30 years, while many other chemical parameters generally showed linear effects for 30–45 years after intensified harvesting. Exchangeable acidity (EA), BS and pH all showed the reversed effect with time, i.e. an initial increase and then gradual decrease over 24–45 years. The subsoil never showed a significant temporal effect. Our results generally support greater reductions in nutrient concentrations, SOC and total N in forest soil after WTH compared with SOH in northern temperate and boreal forest ecosystems.

• Mundra, Sunil; Kjønaas, O. Janne; Morgado, Luis; Krabberød, Anders Kristian; Ransedokken, Yngvild & Kauserud, Håvard (2021). Soil depth matters: shift in composition and inter-kingdom co-occurrence patterns of microorganisms in forest soils. FEMS Microbiology Ecology. ISSN 0168-6496. 97(3). doi: 10.1093/femsec/fiab022. Fulltekst i vitenarkiv Vis sammendrag

  Soil depth represents a strong physiochemical gradient that greatly affects soil-dwelling microorganisms. Fungal communities are typically structured by soil depth, but how other microorganisms are structured is less known. Here, we tested whether depth-dependent variation in soil chemistry affects the distribution and co-occurrence patterns of soil microbial communities. This was investigated by DNA metabarcoding in conjunction with network analyses of bacteria, fungi, as well as other micro-eukaryotes, sampled in four different soil depths in Norwegian birch forests. Strong compositional turnover in microbial assemblages with soil depth was detected for all organismal groups. Significantly greater microbial diversity and fungal biomass appeared in the nutrient-rich organic layer, with sharp decrease towards the less nutrient-rich mineral zones. The proportions of copiotrophic bacteria, Arthropoda and Apicomplexa were markedly higher in the organic layer, while patterns were opposite for oligotrophic bacteria, Cercozoa, Ascomycota and ectomycorrhizal fungi. Network analyses indicated more intensive inter-kingdom co-occurrence patterns in the upper mineral layer (0–5 cm) compared to the above organic and the lower mineral soil, signifying substantial influence of soil depth on biotic interactions. This study supports the view that different microbial groups are adapted to different forest soil strata, with varying level of interactions along the depth gradient.

• Bright, Ryan M.; Allen, Micky; Antón-Fernández, Clara; Belbo, Helmer; Dalsgaard, Lise & Eisner, Stephanie [Vis alle 10 forfattere av denne artikkelen] (2020). Evaluating the terrestrial carbon dioxide removal potential of improved forest management and accelerated forest conversion in Norway. Global Change Biology. ISSN 1354-1013. 26(9), s. 5087–5105. doi: 10.1111/gcb.15228. Fulltekst i vitenarkiv Vis sammendrag

  As a carbon dioxide removal measure, the Norwegian government is currently considering a policy of large-scale planting of spruce (Picea abies (L) H. Karst) on lands in various states of natural transition to a forest dominated by deciduous broadleaved tree species. Given the aspiration to bring emissions on balance with removals in the latter half of the 21st century in effort to limit the global mean temperature rise to “well below” 2°C, the effectiveness of such a policy is unclear given relatively low spruce growth rates in the region. Further convoluting the picture is the magnitude and relevance of surface albedo changes linked to such projects, which typically counteract the benefits of an enhanced forest CO2 sink in high-latitude regions. Here, we carry out a rigorous empirically based assessment of the terrestrial carbon dioxide removal (tCDR) potential of large-scale spruce planting in Norway, taking into account transient developments in both terrestrial carbon sinks and surface albedo over the 21st century and beyond. We find that surface albedo changes would likely play a negligible role in counteracting tCDR, yet given low forest growth rates in the region, notable tCDR benefits from such projects would not be realized until the second half of the 21st century, with maximum benefits occurring even later around 2150. We estimate Norway's total accumulated tCDR potential at 2100 and 2150 (including surface albedo changes) to be 447 (±240) and 852 (±295) Mt CO2-eq. at mean net present values of US$ 12 (±3) and US$ 13 (±2) per ton CDR, respectively. For perspective, the accumulated tCDR potential at 2100 represents around 8 years of Norway's total current annual production-based (i.e., territorial) CO2-eq. emissions.

• Veerman, Liz; Kalbitz, Karsten; Gundersen, Per; Kjønaas, O. Janne; Moldan, Filip & Schleppi, Patrick [Vis alle 10 forfattere av denne artikkelen] (2020). The long-term fate of deposited nitrogen in temperate forest soils. Biogeochemistry. ISSN 0168-2563. 150(1), s. 1–15. doi: 10.1007/s10533-020-00683-6. Fulltekst i vitenarkiv Vis sammendrag

  Increased anthropogenic nitrogen (N) inputs can alter the N cycle and affect forest ecosystem functions. The impact of increased N deposition depends among others on the ultimate fate of N in plant and soil N pools. Short-term studies (3-18 months) have shown that the organic soil layer was the dominant sink for N. However, longer time scales are needed to investigate the long-term fate of N. Therefore, the soils of four experimental forest sites across Europe were re-sampled similar to 2 decades after labelling with(15)N. The sites covered a wide range of ambient N deposition varying from 13 to 58 kg N ha(-1)year(-1). To investigate the effects of different N loads on(15)N recovery, ambient N levels were experimentally increased or decreased. We hypothesized that: (1) the mineral soil would become the dominant(15)N sink after 2 decades, (2) long-term increased N deposition would lead to lower(15)N recovery levels in the soil and (3) variables related to C dynamics would have the largest impact on(15)N recovery in the soil. The results show that large amounts of the added(15)N remain in the soil after 2 decades and at 2 out of 4 sites the(15)N recovery levels are higher in the mineral soil than in the organic soil. The results show no clear responses of the isotopic signature to the changes in N deposition. Several environmental drivers are identified as controlling factors for long-term(15)N recovery. Most drivers that significantly contribute to(15)N recovery are strongly related to the soil organic matter (SOM) content. These findings are consistent with the idea that much of the added(15)N is immobilized in the SOM. In the organic soil layer, we identify C stock, thickness of the organic layer, N-status and mean annual temperature of the forest sites as most important controlling factors. In the mineral soil we identify C stock, C content, pH, moisture content, bulk density, temperature, precipitation and forest stand age as most important controlling factors. Overall, our results show that these temperate forests are capable of retaining long-term increased N inputs preferably when SOM availability is high and SOM turnover and N availability are low.

• Mundra, Sunil; Morgado, Luis Neves; Kjønaas, O. Janne & Kauserud, Håvard (2018). Soil depth matters: Bacteria, fungi and micro-eukaryotes are all strongly structured by soil depth. I Kettunen, Krista & Kiikkilä, Oili (Red.), 3rd Conference on Ecology of Soil Microorganisms 2018. LUKE. ISSN 9789523265844. s. 157–157. Fulltekst i vitenarkiv Vis sammendrag

  The boreal forest is a key ecosystem for global C sequestration and storage. Microorganisms in soil have crucial functions in regulating these processes. Fungi are typically sharply structured with soil depth, but we largely lack such information for other microorganism, including bacteria and other micro-eukaryotes. To improve our knowledge of how different microorganisms are structured vertically and how they might interact, we investi-gated the communities of bacteria, fungi and micro-eukaryotes in four different soil horizons in natural birch forests in Western Norway. The communities of all three organismal groups were strongly structured along the vertical depth. Our results support the hypothesis that natural decrease in nutrient availability and pH differ-ences between organic and mineral horizons affect the distribution of soil microorganisms. Proteobacteria, Actinobacteria and Planctomycetes dominated in the uppermost organic layer while Acidobacteria and Firmicu-tes in mineral layers. Proportionally, fungi dominated in mineral layers whereas other micro-eukaryotes (Meta-zoa, Apicomplexa, Conosa, Ochrophyta and Chlorophyta) in organic layers. Ascomycota were relatively more abundant in mineral layers compared to Basidiomycota and Cryptomycota. Nematoda, Annelida and Arthropo-da showed decreasing trends with depth. Furthermore, different optima in the depth distribution of ectomy-corrhizal and saprotrophic genera was observed, supporting the view that different genera are adapted to different niches along the soil depth gradient. Network analyses will be used to infer tentative biotic interac-tions between the microbial groups and how this varies with soil depth.

• Kjønaas, O. Janne; Mundra, Sunil; Bárcena, Teresa G.; Hansen, Mette; Hylen, Gro & Kauserud, Håvard (2018). How does tree species change affect forest soil C stocks, C mineralization rates, organic matter stability and microbial diversity? I Kettunen, Krista & Kiikkilä, Oili (Red.), 3rd Conference on Ecology of Soil Microorganisms 2018. LUKE. ISSN 9789523265844. s. 134–134. Fulltekst i vitenarkiv Vis sammendrag

  Tree species change has been suggested as one of the government policies to mitigate climate change in Nor-way with the aim to increase the annual uptake of CO2 and the long-term storage of carbon (C) in forests. The strategy includes replacing native, deciduous species with fast-growing species, mainly Norway spruce. A shift in tree species is expected to affect the pools and fluxes of C in the stand as well as the microbial community. As part of the BalanC project, we assess C storage related to shift in tree species cover in western Norway and whether a corresponding shift in soil microbial communities are happening. The study aim at integrating results on soil respiration, C mineralization, soil stability, diversity of bacteria, fungi and micro-eukaryotes, soil nutrient pools, litter inputs and edaphic factors at the stand level in order to identify key drivers for changes in the soil C stocks. Fifteen paired plots of native birch and planted Norway spruce at five locations were sampled. Prelimi-nary results suggests a redistribution of C from the mineral soil to the forest floor in the spruce stands, with minor changes in the total soil C pools over the 45-60 years since the tree species change. The in situ soil respi-ration and heterothropic respiration, as well as C mineralization rates, were higher in birch than in spruce stands. Differences in C mineralization rates attenuate with depth between forest types. The microbial com-munities of the three organismal groups were all strongly structured along the vertical depth.

• Clarke, Nicholas; Skår, Silje; Kjønaas, O. Janne; Hanssen, Kjersti Holt; Økland, Tonje & Nordbakken, Jørn-Frode [Vis alle 8 forfattere av denne artikkelen] (2018). Effects of forest residue harvesting on short-term changes in soil solution chemistry. Scandinavian Journal of Forest Research. ISSN 0282-7581. 33(3), s. 299–307. doi: 10.1080/02827581.2017.1375141. Fulltekst i vitenarkiv Vis sammendrag

  Short-term (three to four years) effects of forest harvesting on soil solution chemistry were investigated at two Norway spruce sites in southern Norway, differing in precipitation amount and topography. Experimental plots were either harvested conventionally (stem-only harvesting, SOH) or whole trees, including crowns, twigs and branches were removed (whole-tree harvesting, WTH), leaving residue piles on the ground for some months before removal. The WTH treatment had two sub-treatments: WTH-pile where there had been piles and WTH-removal, from where residues had been removed to make piles. Increased soil solution concentrations of NO3–N, total N, Ca, Mg and K at 30 cm depth, shown by peaks in concentrations in the years after harvesting, were found at the drier, less steep site in eastern Norway after SOH and WTH-pile, but less so after WTH-removal. At the wetter, steeper site in western Norway, peaks were often observed also at WTH-removal plots, which might reflect within-site differences in water pathways due largely to site topography.

• Eldhuset, Toril Drabløs; Kjønaas, O. Janne & Lange, Holger (2017). Decomposition rates and nutrient dynamics of Picea abies needles, twigs and fine roots after stem-only harvesting in eastern and western Norway. Plant and Soil. ISSN 0032-079X. 418(1-2), s. 357–375. doi: 10.1007/s11104-017-3302-1. Fulltekst i vitenarkiv Vis sammendrag

  Background and aims Decomposition of the finest harvest residues is important for the carbon and nutrient cycle in forest ecosystems both before and after tree felling. We assumed that decomposition is dependent on harvest residue fraction and chemistry, soil temperature and moisture, and aimed at determining decomposition rates and nutrient dynamics of needles, twigs and fine roots from newly felled Picea abies trees in two sites with different climate and topography. Methods Decomposition of needles, twigs and fine roots in mesh bags was followed for up to six years and four years in harvesting sites in eastern and western Norway, respectively. The western site had a more humid climate and a steeper terrain than the eastern site. Results The mass loss after two years was significantly higher for needles (49–59%) than for twigs and fine roots (29–38%). Between sites, there was no significant difference between mass loss for neither needles nor twigs. Nitrogen accumulated in needles during the first year, but 35% of initial needle N had been released after three years. The initial needle and twig decomposition rate was dependent on soil moisture and topographic aspect. During the first three years, needle lignin concentrations retarded whereas P concentrations stimulated needle mass loss. For twigs, P concentrations stimulated mass loss, whereas higher soil temperatures reduced it. Conclusions Lignin and P concentrations of plant parts and soil temperature were the most important factors for the first three-year mass loss. The slow release of nutrients shows the importance of remaining needles, twigs and fine roots as a long-time nutrient source in the ecosystems under study.

• Kjønaas, O. Janne; Økland, Tonje; Andreassen, Kjell; Stuanes, Arne; Nordbakken, Jørn-Frode & Lange, Holger [Vis alle 7 forfattere av denne artikkelen] (2017). Repeated sampling of two tree species experiments in S.E. Norway. I Dalsgaard, Lise; Lange, Holger & Kjønaas, O. Janne (Red.), Forest soil carbon changes from measurements and models - Site-specific comparisons and implications for UNFCCC reporting. NIBIO. ISSN 9788217019350. s. 18–58. Fulltekst i vitenarkiv Vis sammendrag

  For å verifisere beregningsmetoder og modeller for endringer av karbonlagre i skogsjord brukt i UNFCCC rapporteringen er det behov for data fra jordprøver med gjentak over tid og der prøvetakingsmetoder er konsistente. I Norge finnes ikke denne typen data på nasjonalt / landsdekkende nivå. For å møte behovet for verifisering av beregningsmetodikken brukt i UNFCCC rapporteringen innenfor rammene av eksisterende data med metodisk konsistens over tid, er det i denne undersøkelsen gjennomført ny prøvetaking av jord og vegetasjon i to etablerte forsøksfelt i skog i sør-øst Norge der vi fra før av både har data fra tidligere jordprøveanalyser og tilvekstdata for trær i skogsbestand. De to forsøksfeltene ligger på Nordmoen i Akershus (etablert 1973 og tilplantet 1974) og i Skiptvet i Østfold (etablert 1976 i eksisterende foryngelse med supplerplanting i 1977). Med nye jordprøver, biomassemålinger og vegetasjonsanalyser i 2011 gir dette to tidsserier på hhv. 38 og 34 år med hensyn på endringer i jordkarbon og inngangsverdier i beregningsmodellene. Den eksperimentelle behandlingen i Skiptvet omfatter ulik grad av treslagsblanding av bjørk og gran på de enkelte forsøksrutene, mens på Nordmoen sammenliknes rene bestand av hhv. bjørk, gran og furu. De klimatiske forhold er tilnærmet like, mens jordsmonntypen er ulik med næringsfattig sandjord på Nordmoen og næringsrik leirjord i Skiptvet. Resultatene fra forsøkene er begrenset til å representere klimatiske og vegetasjonsmessige forhold på Østlandet (og forhold tilsvarende de to lokalitetene), og forsøksfeltene er dermed ikke representative eksempelvis for kystnære og kontinentale strøk.

• Vanguelova, Elena Iordanova; Bonifacio, Eleonora; Vos, Bruno de; Hoosbeek, Marcel R.; Berger, Torsten W. & Vesterdal, Lars [Vis alle 17 forfattere av denne artikkelen] (2016). Sources of errors and uncertainties in the assessment of forest soil carbon stocks at different scales—review and recommendations. Environmental Monitoring and Assessment. ISSN 0167-6369. 188(11). doi: 10.1007/s10661-016-5608-5. Fulltekst i vitenarkiv Vis sammendrag

  Spatially explicit knowledge of recent and past soil organic carbon (SOC) stocks in forests will improve our understanding of the effect of human- and non-human-induced changes on forest C fluxes. For SOC accounting, a minimum detectable difference must be defined in order to adequately determine temporal changes and spatial differences in SOC. This requires sufficiently detailed data to predict SOC stocks at appropriate scales within the required accuracy so that only significant changes are accounted for. When designing sampling campaigns, taking into account factors influencing SOC spatial and temporal distribution (such as soil type, topography, climate and vegetation) are needed to optimise sampling depths and numbers of samples, thereby ensuring that samples accurately reflect the distribution of SOC at a site. Furthermore, the appropriate scales related to the research question need to be defined: profile, plot, forests, catchment, national or wider. Scaling up SOC stocks from point sample to landscape unit is challenging, and thus requires reliable baseline data. Knowledge of the associated uncertainties related to SOC measures at each particular scale and how to reduce them is crucial for assessing SOC stocks with the highest possible accuracy at each scale. This review identifies where potential sources of errors and uncertainties related to forest SOC stock estimation occur at five different scales—sample, profile, plot, landscape/regional and European. Recommendations are also provided on how to reduce forest SOC uncertainties and increase efficiency of SOC assessment at each scale.

• Vanguelova, Elena I.; Bonifacio, Eleonora; Vos, Bruno De; Hoosbeek, Marcel R.; Berger, Torsten W. & Vesterdal, Lars [Vis alle 17 forfattere av denne artikkelen] (2016). Sources of errors and uncertainties in the assessment of forest soil carbon stocks at different scales—review and recommendations. Environmental Monitoring and Assessment. ISSN 0167-6369. 188(11). doi: 10.1007/s10661-016-5608-5. Fulltekst i vitenarkiv
• Berg, Bjørn; Kjønaas, O. Janne; Johansson, Maj-Britt; Erhagen, Bjørn & Åkerblom, Staffan (2015). Late stage pine litter decomposition: Relationship to litter N, Mn, and acid unhydrolyzable residue (AUR) concentrations and climatic factors. Forest Ecology and Management. ISSN 0378-1127. 358, s. 41–47. doi: 10.1016/j.foreco.2015.08.032. Fulltekst i vitenarkiv Vis sammendrag

  The aim of this paper is to evaluate relationships between decomposition rates of Scots pine (Pinus sylvestris) and lodgepole pine (Pinus contorta var. contorta) needle litter in the late stage of decomposition (>30% accumulated mass loss), and the progressively changing concentrations of manganese (Mn), nitrogen (N), and acid unhydrolyzable residue (AUR), as well as mean annual temperature (MAT) and mean annual precipitation (MAP). Using available long-term decomposition studies on pine needle litter in a climate gradient in Sweden, we calculated annual mass loss and related to concentrations of Mn, N, and AUR at the start of each one-year period as well as to MAT and MAP. We investigated these relationships for (i) all data on annual mass loss combined and (ii) annual mass loss for five different decomposition categories as defined by accumulated mass loss. We found highly significant, negative, and dominant relationships between annual mass loss and N (R2 = 0.39) and AUR (R2 = 0.39), a slight but significant positive relationship to Mn (R2 = 0.08) and a significant negative relationship to MAT (R2 = 0.06). The relationships were dynamic, and changed with accumulated mass loss. The rate-dampening effect of N decreased to be a rate-enhancing effect at c. 60–80% accumulated mass loss. A similar trend was found for AUR, becoming rate-enhancing at 70–80% accumulated mass loss. For Scots pine needle litter the effect of MAT on mass loss decreased with increasing accumulated mass loss and changed to a rate-dampening effect at c. 50–70% accumulated mass loss. Mn showed a stimulating effect on mass loss rate in all categories whereas MAP showed no effect in this mainly boreal climatic gradient. The current approach indicates a method for detailed studies of rate-regulating factors for litter decomposition.

• Clarke, Nicholas; Gundersen, Per; Jönsson-Belyazid, Ulrika; Kjønaas, O. Janne; Persson, Tryggve & Sigurðsson, Bjarni Diðrik [Vis alle 8 forfattere av denne artikkelen] (2015). Influence of different tree-harvesting intensities on forest soil carbon stocks in boreal and northern temperate forest ecosystems. Forest Ecology and Management. ISSN 0378-1127. 351, s. 9–19. Fulltekst i vitenarkiv
• Clarke, Nicholas; Gundersen, Per; Jönsson-Belyazid, Ulrika; Kjønaas, O. Janne; Persson, Tryggve & Sigurðsson, Bjarni Diðrik [Vis alle 8 forfattere av denne artikkelen] (2015). Influence of different tree-harvesting intensities on forest soil carbon stocks in boreal and northern temperate forest ecosystems. Forest Ecology and Management. ISSN 0378-1127. 351, s. 9–19. doi: 10.1016/j.foreco.2015.04.034. Fulltekst i vitenarkiv

Se alle arbeider i NVA

• Dalen, Lars Sandved; Hanssen, Kjersti Holt & Kjønaas, Janne (2025). Markberedning og skogens karbonlager - Nibio. [Internet]. nibio.no. Fulltekst i vitenarkiv Vis sammendrag

  Hvordan påvirker egentlig markberedning skogens karbonlager? To hogstflater i Innlandet skal bidra til svaret.

• Dalen, Lars Sandved; Kjønaas, Janne & Hanssen, Kjersti Holt (2025). Markberedning og karbon. [Journal]. Magasinet Skog. doi: https:/skog.no/e-magasin/. Fulltekst i vitenarkiv Vis sammendrag

  Hvordan påvirker egentlig markberedning skogens karbonlager? To hogstflater i Innlandet skal bidra til svaret.

• Dalen, Lars Sandved; Kjønaas, Janne & Hanssen, Kjersti Holt (2025). Hvordan påvirker markberedning karbonlagring i skogsjord? [Internet]. Magasinet Treindustrien. Fulltekst i vitenarkiv Vis sammendrag

  Utforsk hvordan markberedning påvirker karboninnholdet i skogsjord og økosystemet. Lær om forskningsprosjektet ledet av Nibio og de to metodene for markberedning.

• Hanssen, Kjersti Holt; Kjønaas, O. Janne & Dalen, Lars Sandved (2025). Markberedning og skogens karbonlager. [Journal]. Norsk Skogbruk. Fulltekst i vitenarkiv
• Ronold, Eivind Kverme; Maurice, Sundy; Torp, Vilde Åvesland; Kostich-Nilsen, Celina Alexandria; Methlie, Ine-Susanne Hopland & Schmidt, Frida [Vis alle 17 forfattere av denne artikkelen] (2024). USING eDNA TO ASSESS THE EFFECTS OF CLEAR-CUTTING FORESTRY ON FUNGAL DIVERSITY IN BOREAL SPRUCE FORESTS. Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Bright, Ryan M.; Hylen, Gro; Barcena, Teresa Gomez de la; Nordbakken, Jørn-Frode & Økland, Tonje [Vis alle 11 forfattere av denne artikkelen] (2023). Effects of tree species change on climate change mitigation, soil dynamics and biodiversity in Western Norway (BalanC): Short- and long-term perspectives. Fulltekst i vitenarkiv
• Kjønaas, O. Janne (2023). Skogbruk og karbonlagre i et klimaperspektiv. Fulltekst i vitenarkiv
• Dalsgaard, Lise; Hagenbo, Andreas; Hasegawa, Shun; Kjønaas, O. Janne & Mohr, Christian Wilhelm (2023). National scale soil carbon changes in forest for the LULUCF – what we do and where we are going. Fulltekst i vitenarkiv
• Kjønaas, O. Janne (2023). Jordkarbonets betydning i klimasammenheng og skogbrukets påvirkning. Fulltekst i vitenarkiv
• Malicki, Brunon; Morgado, Luis; Nordén, Jenni; Bjorbækmo, Marit Frederikke Markussen; Skarpaas, Olav & Kjønaas, O. Janne [Vis alle 8 forfattere av denne artikkelen] (2022). Factors driving the diversity of eukaryotic microorganisms in boreal forest soils. Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Simonsen, Morten; Hylen, Gro; Barcena, Teresa G. & Aall, Carlo (2022). Karbonbinding i Vestlandsskogen. Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Hylen, Gro; Barcena, Teresa G.; Simonsen, Morten & Aall, Carlo (2022). Effekter av treslagsskifte fra bjørk til gran på jordkarbon - Resultater fra BalanC. Fulltekst i vitenarkiv
• Kjønaas, O. Janne (2022). Karbonbinding og jordhelse i skogbruket. Fulltekst i vitenarkiv
• Aall, Carlo & Kjønaas, O. Janne (2022). Usikker klimagevinst av granplanting i vest? Fulltekst i vitenarkiv
• Dalsgaard, Lise; Kjønaas, O. Janne & Mohr, Christian Wilhelm (2022). Karbon i norsk skogsjord - hvor godt er det norske klimagassregnskapet på jordkarbon? Fulltekst i vitenarkiv
• Dalsgaard, Lise & Kjønaas, O. Janne (2022). Preparations of a national scale soil carbon monitoring program for forest and grassland in Norway. Fulltekst i vitenarkiv
• Clarke, Nicholas; Kiær, Lars Pødenphant; Kjønaas, O. Janne; Barcena, Teresa G.; Vesterdal, Lars & Stupak, Inge [Vis alle 12 forfattere av denne artikkelen] (2021). Effects of intensive biomass harvesting on forest soils in the Nordic countries and the UK: A meta-analysis. Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Barcena, Teresa G.; Hylen, Gro; Nordbakken, Jørn-Frode; Økland, Tonje & Kauserud, Håvard [Vis alle 7 forfattere av denne artikkelen] (2021). Hvordan påvirker treslagsskifte karbonbinding og biomangfold? Fulltekst i vitenarkiv
• Kjønaas, O. Janne (2021). Treslagskifte og karbon: Høyere karbonfangst, men usikre lagre. [Journal]. Norsk skogbruk. Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Mundra, Sunil & Kauserud, Håvard (2021). Climate change mitigation and tree species change - time perspectives and potential tradeoffs. Fulltekst i vitenarkiv
• Kjønaas, O. Janne (2020). Karbonbalansen i skogjord. Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Bárcena, Teresa G.; Bright, Ryan M.; Hansen, Mette; Hylen, Gro & Kauserud, Håvard [Vis alle 11 forfattere av denne artikkelen] (2020). BalanC - The impact of increasing spruce plantation area on the carbon balance of forests in Western Norway. Preliminary conclusions. Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Bárcena, Teresa G.; Bright, Ryan M.; Hansen, Mette; Hylen, Gro & Kauserud, Håvard [Vis alle 11 forfattere av denne artikkelen] (2020). Treslagsskifte som klimatiltak. Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Bright, Ryan M.; Hylen, Gro; Bárcena, Teresa G.; Økland, Tonje & Nordbakken, Jørn-Frode [Vis alle 11 forfattere av denne artikkelen] (2020). Karbonbalansen i skog på Vestlandet. Fulltekst i vitenarkiv
• Kjønaas, O. Janne (2020). Hvordan kan hogst, treslagsskifte og rotasjonslengde påvirke klimagassutslipp, karbonkretsløp, næringstilgjengelighet og biodiversitet i skogsjorda? Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Bárcena, Teresa G.; Bright, Ryan M.; Hansen, Mette; Hylen, Gro & Kauserud, Håvard [Vis alle 10 forfattere av denne artikkelen] (2019). Karbonbalanse og treslagsskifte - foreløpig resultater fra BalanC. Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Bárcena, Teresa G.; Bright, Ryan M.; Hansen, Mette; Hylen, Gro & Kauserud, Håvard [Vis alle 10 forfattere av denne artikkelen] (2019). Carbon balance and tree species change – preliminary results from BalanC. Fulltekst i vitenarkiv
• Mundra, Sunil; Morgado, Luis Neves; Kauserud, Håvard & Kjønaas, O. Janne (2019). Compositional shift in communities of bacteria and fungi following tree species change from unmanaged birch to managed spruce forest. Fulltekst i vitenarkiv
• Hansen, Mette; Bárcena, Teresa G. & Kjønaas, O. Janne (2019). Changes in SOM composition and stability following tree species change from unmanaged birch to managed spruce forest in Western Norway. Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Ostonen, Ivika; Vesterdal, Lars; Laiho, Raija; Larmola, Tuula & Oddsdóttir, Edda S. [Vis alle 8 forfattere av denne artikkelen] (2019). The functional biodiversity survey – results and way forward. Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Bárcena, Teresa G.; Bright, Ryan M.; Hanssen, Mette; Hylen, Gro & Kauserud, Håvard [Vis alle 10 forfattere av denne artikkelen] (2019). The impact of increasing spruce plantation area on the carbon balance of forests in Western Norway – BalanC. Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Bárcena, Teresa G.; Mette, Hansen; Mundra, Sunil; Kauserud, Håvard & Hylen, Gro [Vis alle 8 forfattere av denne artikkelen] (2019). Effects of tree species change on soil characteristics in Western Norway - BalanC. Fulltekst i vitenarkiv
• Mundra, Sunil; Morgado, Luis Neves; Kjønaas, O. Janne & Kauserud, Håvard (2018). Community of bacteria, fungi and micro-eukaryotes structured along soil forest stratification. Fulltekst i vitenarkiv
• Mundra, Sunil; Morgado, Luis Neves; Kjønaas, O. Janne & Kauserud, Håvard (2018). Soil depth matters: Bacteria, fungi and micro-eukaryotes are strongly structured by soil Depth. Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Mundra, Sunil; Bárcena, Teresa G.; Hansen, Mette; Hylen, Gro & Kauserud, Håvard (2018). How does tree species change affect forest soil C stocks, C mineralization rates, organic matter stability and microbial diversity? Fulltekst i vitenarkiv
• Økland, Tonje; Nordbakken, Jørn-Frode & Kjønaas, O. Janne (2018). BalanC Task: Understory vegetation main results Annual Project meeting. Fulltekst i vitenarkiv
• Mundra, Sunil; Morgado, Luis Neves; Kjønaas, O. Janne & Kauserud, Håvard (2018). Compositional shift in communities of bacteria and fungi following tree species change from unmanaged birch to managed spruce forest. Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Bárcena, Teresa G. & Hylen, Gro (2018). Carbon stocks and soil respiration rates in paired stands of birch and spruce in Western Norway. Preliminary results from the BalanC project. Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Hylen, Gro; Bright, Ryan M.; Nordbakken, Jørn-Frode; Økland, Tonje & Bárcena, Teresa G. [Vis alle 7 forfattere av denne artikkelen] (2018). Kva veit vi om karbonbindinga i skog,og kva betyr det for skogsforvaltinga? Fulltekst i vitenarkiv
• Kløvstad, Astri & Kjønaas, O. Janne (2017). Karbonbalansen under lupen. [Journal]. Norsk Skogbruk. Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Bárcena, Teresa G. & Hylen, Gro (2017). Effects of tree species change on forest soil carbon in Western Norway (BalanC)- preliminary results. Fulltekst i vitenarkiv
• Lange, Holger; Clarke, Nicholas; Kjønaas, O. Janne; Nordbakken, Jørn-Frode; Sippel, Sebastian & Økland, Tonje (2017). Skogens rolle for karbonbinding og som klimatiltak. Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Bárcena, Teresa G.; Bright, Ryan Matthew & Aall, Carlo (2016). Vi vet for lite om hvordan jorda i skogen påvirker klimaet. Fulltekst i vitenarkiv
• Kjønaas, O. Janne & Sandvik, Gunnar (2016). Skogforskarar skal undersøkje karbonlagring. [TV]. NRK Møre og Romsdal. Fulltekst i vitenarkiv
• Kjønaas, O. Janne & Sandvik, Gunnar (2016). Skogforskerne vil grave i skogen. [Internet]. NRK Møre og Romsdal. Fulltekst i vitenarkiv
• Økland, Tonje; Nordbakken, Jørn-Frode; Lange, Holger; Røsberg, Ingvald; Kjønaas, O. Janne & Hanssen, Kjersti Holt [Vis alle 7 forfattere av denne artikkelen] (2016). Removing forest harvesting residuals: effects on biodiversity and species composition in Norwegian forests. Fulltekst i vitenarkiv
• Clarke, Nicholas; Cross, Hugh; Eldhuset, Toril Drabløs; Hanssen, Kjersti Holt; Hietala, Ari Mikko & Kjønaas, O. Janne [Vis alle 11 forfattere av denne artikkelen] (2016). Short-term ecological consequences of removal of harvesting residues for bioenergy from forests in Norway. Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Clarke, Nicholas; Eldhuset, Toril Drabløs; Hietala, Ari Mikko; Cross, Hugh & Hanssen, Kjersti Holt [Vis alle 10 forfattere av denne artikkelen] (2015). Short-term effects of whole-tree and stem-only harvesting on C and N fluxes in two Picea abies stands, Norway. Geophysical Research Abstracts. ISSN 1029-7006. 17, s. 10416–10416. Fulltekst i vitenarkiv Vis sammendrag

  Tree harvest and different harvesting methods may affect the soil carbon (C) pool in forest ecosystems. In con- ventional stem-only timber harvesting (SOH), branches and tops that are left in the forests may contribute to the build-up of the soil carbon pool. In whole-tree harvesting (WTH), inputs of organic matter from branches and tops are strongly reduced. We established field experiments at Gaupen, SE and Vindberg, SW Norway, to study the short-term effects of SOH and WTH on processes affecting the accumulation and loss of soil C. Logging residues on the WTH plots were collected in piles that were removed after 6 months, rendering two sub treatments (WTH- pile and WTH-removal areas). We weighed selected trees and logging residues, surveyed understorey biomass production, quantified pre-harvest soil C and nutrient pools down to 30 cm. Soil respiration was measured and soil water sampled monthly during the growing season, while temperature and moisture were measured continuously. Organic and mineral horizons were incubated at different temperatures to estimate potential C and N mineraliza- tion, and deep sequencing of the ITS2 barcode region of fungal DNA was performed on the samples. Litterbags were deployed in the SOH plots. The logging residues amounted to 2.2-2.4 kg C m-2 At Gaupen, the mean in situ soil respiration rates increased following harvest with all treatments, but were significantly higher in WTH-pile and SOH relative to the WTH- removal areas in the first year as well as the fourth year of treatment. The former rates included aboveground decomposing needles and twigs but excluded coarser branches. The observed increase in the WTH-removal areas may be related to decomposing roots, as well as to increased C mineralization partly due to the higher soil tem- peratures following harvest. Soil temperature was the single most important factor explaining the variability in soil respiration rates over all treatments. At Vindberg, a decrease in soil respiration was observed with all treatments in the second and third years following harvest. At both sites, decomposition of logging residues from needles was more rapid relative to twigs and fine roots. The decomposing residues released a substantial amount of nitrogen which was gradually reflected in the soil water at 30 cm soil depth. A considerable increase in the NO3-N concen- tration also in the WTH-removal areas in the second year following harvest suggests an increase in N availability from decomposing fine roots and/or soil organic matter. The increased N availability in the WTH-removal areas was supported by results from short term lab incubations of undisturbed soil from the forest floor. The changes in the WTH-removal areas were also reflected in the soil fungal diversity: saprophytic ascomycetes on decaying plant material showed a striking increase in all treatments. For the WTH-removal areas, this may, again, be related to the increased input of root litter; however, the decrease in mycorrhizal basidiomycete species and the vigorous increase of ascomycetes following harvest may also affect the C mineralization of soil organic matter.

• Økland, Tonje; Nordbakken, Jørn-Frode; Lange, Holger; Røsberg, Ingvald; Kjønaas, O. Janne & Hanssen, Kjersti Holt [Vis alle 7 forfattere av denne artikkelen] (2015). Effects of whole-tree harvesting and stem-only harvesting on plant biodiversity in Norwegian spruce forest sites. Fulltekst i vitenarkiv Vis sammendrag

  Whole-tree harvest (WTH), i.e. harvesting of forest residues (twigs, branches and crown tops) in addition to stems, for bioenergy purposes may lead to biodiversity loss and changes in species composition in forest ground vegetation, which in turn also will affect soil properties. Effects of clear-cut harvesting on ground vegetation have been investigated at two Norway spruce sites in southern east and western Norway, respectively, differing in climate and topography. Experimental plots at these two sites were either harvested conventionally (stem-only harvest, SOH), leaving harvest residues spread on the site,or WTH was carried out, with the residues collected into piles at the site for six - nine months prior to removal. Vegetation plots in the eastern site were established and analysed before WTH and SOH in 2008 and reanalysed after harvesting in 2010, 2012 and 2014. In the western site vegetation plots were established before WTH and SOH in 2010 and reanalysed after harvesting in 2012 and 2014 (and planned for 2016). All vegetation plots are permanently marked. Pre-as well as post-harvesting species abundances of all species in each vegetation plot were each time recorded as percentage cover (vertical projection) and subplot frequency. Environmental variables (topographical, soil physical, soil chemical, and tree variables) were recorded only once; before WTH and SOH. Effec ts of WTH and SOH on ground vegetation biodiversity and cover are presented.

• Kjønaas, O. Janne; Clark, Nicholas; Eldhuset, Toril Drabløs; Hietala, Ari Mikko; Cross, Hugh & Hansen, Kjersti Holt [Vis alle 10 forfattere av denne artikkelen] (2015). Short-term effects of stem-only and whole-tree harvesting on C and N fluxes in two Picea abies stands, SE and SW Norway. Fulltekst i vitenarkiv
• Vesterdal, Lars; Clarke, Nicholas; Sigurdsson, Bjarni D.; Stefánsdóttir, Helena M; Kjønaas, O. Janne & Gundersen, Per [Vis alle 9 forfattere av denne artikkelen] (2015). Soil carbon sequestration in Nordic forestry: influences of changed land-use and management. Fulltekst i vitenarkiv
• Lange, Holger; Dalsgaard, Lise; Borgen, Signe Kynding; Kjønaas, O. Janne; Callesen, Ingeborg & Liski, Jari [Vis alle 7 forfattere av denne artikkelen] (2015). Soil organic carbon stocks and changes in Norwegian forest ecosystems. Natural resources and bioeconomy studies. ISSN 2342-7639. 29, s. 45–45. Fulltekst i vitenarkiv
• Clarke, Nicholas; Gundersen, Per; Jönsson-Belyazid, Ulrika; Kjønaas, O. Janne; Persson, Tryggve & Sigurdsson, Bjarni D. [Vis alle 8 forfattere av denne artikkelen] (2015). Influence of different tree-harvesting intensities on forest soil carbon stocks in boreal and northern temperate forest ecosystems. Fulltekst i vitenarkiv
• Clarke, Nicholas; Gundersen, Per; Jönsson-Belyazid, Ulrika; Kjønaas, O. Janne; Persson, Tryggve & Sigurdsson, Bjarni D. [Vis alle 8 forfattere av denne artikkelen] (2015). Influence of different tree-harvesting intensities on forest soil carbon stocks in boreal and northern temperate forest ecosystems. Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Clarke, Nicholas; Eldhuset, Toril Drabløs; Hietala, Ari Mikko; Cross, Hugh & Hanssen, Kjersti Holt [Vis alle 10 forfattere av denne artikkelen] (2015). Short-term effects of whole-tree and stem-only harvesting on C and N fluxes in two Picea abies stands, Norway. Geophysical Research Abstracts. ISSN 1029-7006. 17, s. 10416–10416. Fulltekst i vitenarkiv
• Eldhuset, Toril Drabløs; Kjønaas, O. Janne & Lange, Holger (2015). Fine litter decomposition after stem harvest in two Picea abies ecosystems: litterbag studies. Fulltekst i vitenarkiv
• Børja, Isabella; Kjønaas, O. Janne & Dalsgaard, Lise (2014). Når gammel møter ung. Fulltekst i vitenarkiv
• Økland, Tonje; Nordbakken, Jørn-Frode; Lange, Holger; Røsberg, Ingvald; Kjønaas, O. Janne & Hanssen, Kjersti Holt [Vis alle 7 forfattere av denne artikkelen] (2014). Removing forest harvesting residuals: effects on biodiversity and species composition in Norwegian forests. Fulltekst i vitenarkiv
• Clarke, Nicholas; Eldhuset, Toril Drabløs; Hanssen, Kjersti Holt; Kjønaas, O. Janne; Lange, Holger & Nordbakken, Jørn-Frode [Vis alle 8 forfattere av denne artikkelen] (2014). Vi kan få bærekraftig energi fra skog. Aftenposten Viten. ISSN 2464-3033. Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Clarke, Nicholas; Eldhuset, Toril Drabløs; Hietala, Ari Mikko; Cross, Hugh & Økland, Tonje [Vis alle 10 forfattere av denne artikkelen] (2014). Short-term effects of whole tree and stem-only harvesting on C and N fluxes in two Picea abies stands, Norway. Fulltekst i vitenarkiv
• Lange, Holger; Dalsgaard, Lise; Borgen, Signe Kynding; Skår, Silje; Kjønaas, O. Janne & Andreassen, Kjell (2014). Testing of soil carbon models using repeated inventories. Fulltekst i vitenarkiv Vis sammendrag

  Reliable methods are required to predict changes in soil carbon stocks. Process-based models often require many parameters which are largely unconstrained by observations. This induces uncertainties which are best met by using repeated measurements from the same sites. Here, we compare two carbon models, Yasso07 and Romul, in their ability to reproduce a set of field observations in Norway. The models are different in the level of process representation, structure, initialization requirements and calibration- and parameterization strategy. Field sites represent contrasting tree species, mixture and soil types. The number of repetitions of C measurements varies from 2 to 6 over a period of up to 35 years, and for some of the sites, which are part of long-term monitoring programs, plenty of auxiliary information is available. These reduce the danger of overparametrization and provide a stringent testbed for the two models. Focus is on the model intercomparison, using identical site descriptions to the extent possible, but another important aspect is the upscaling of model results to the regional or national scale, utilizing the Norwegian forest inventory system. We suggest that a proper uncertainty assessment of soil C stocks and changes has to include at least two (and preferably more) parametrized models.

• Kjønaas, O. Janne (2014). Carbon storage in forests. Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Clark, Nicholas; Eldhuset, Toril Drabløs & Hietala, Ari Mikko (2014). Virkninger av økt biomasseuttak på jord, jordvann og sopp: Prosjektet Ecobrem WP I. Fulltekst i vitenarkiv
• Clarke, Nicholas; Eldhuset, Toril Drabløs; Kjønaas, O. Janne; Økland, Tonje; Hanssen, Kjersti Holt & Aas, Wenche [Vis alle 20 forfattere av denne artikkelen] (2014). Praktiske råd for bærekraftig uttak av grot – hvilke konklusjoner kan vi trekke? Fulltekst i vitenarkiv
• Kjønaas, O. Janne; Clarke, Nicholas; Eldhuset, Toril Drabløs; Hanssen, Kjersti Holt; Hietala, Ari Mikko & Lange, Holger [Vis alle 9 forfattere av denne artikkelen] (2014). Short-term effects of whole tree and stem-only harvesting on C and N fluxes in two Picea abies stands, Norway. International forestry review. ISSN 1465-5489. 16(5), s. 363–364. Fulltekst i vitenarkiv
• Økland, Tonje; Nordbakken, Jørn-Frode; Lange, Holger; Røsberg, Ingvald; Kjønaas, O. Janne & Clarke, Nicholas [Vis alle 7 forfattere av denne artikkelen] (2014). Removing forest harvesting residuals: effects on biodiversity and species composition in Norwegian forests. International forestry review. ISSN 1465-5489. 16(5), s. 518–518. Fulltekst i vitenarkiv
• Hasegawa, Shun; Stupak, Inge; Baldursdóttir, Kristin; Ilvesniemi, Hannu; Johannesson, Carl-Fredrik & Kjønaas, Janne [Vis alle 16 forfattere av denne artikkelen] (2025). Harmonising forest soil carbon monitoring systems across countries - Opportunities and Challenges. NIBIO. ISSN 9788217038245. Fulltekst i vitenarkiv Vis sammendrag

  Bakgrunn: Overvåking av karbon i skogjord gjennomføres i mange land, noe som har resultert i omfattende nasjonale datasett, også i tilfelle hvor landene har felles grenser og i stor utstrekning lignende eller tilsvarende skogs- og jordtyper. Mulighet: Internasjonalt samarbeid om data og feltmetoder kan legge til rette for integrasjon av datasett og sammenligning av overvåkingsdata til støtte for utvikling av internasjonal politikk i et multinasjonalt fremfor et nasjonalt perspektiv. Utfordring: Variasjoner i overvåkingsmetodikk mellom land må håndteres for å kunne gjennomføre en effektiv syntese av data om karbon i skogjord. Tilnærming: Hvert land har utviklet sitt eget overvåkingsprogram for å møte spesifikke og nasjonale miljømessige og institusjonelle behov, noe som har ført til omfattende datasett på nasjonalt nivå. Harmonisering kan bidra til å realisere det fulle potensialet i disse nasjonale datasettene gjennom utvikling av internasjonale referansedefinisjoner. En tilnærming med utgangspunkt i harmonisering tillater nasjonal tilpasning, samtidig med at data kan brukes i en internasjonal kontekst, i kontrast til standardisering og en «én størrelse passer alle»-tilnærming.

• Søgaard, Gunnhild; Bright, Ryan M.; Clarke, Nicholas; Fløistad, Inger; Granhus, Aksel & Hagenbo, Andreas [Vis alle 15 forfattere av denne artikkelen] (2023). Oppdatering av kunnskapsgrunnlag for klimatiltak i skog: Gjennomgang av 11 utvalgte tiltak i bestandsskogbruket. NIBIO. Fulltekst i vitenarkiv Vis sammendrag

  På oppdrag fra Miljødirektoratet og Landbruksdirektoratet har vi gått gjennom kunnskapsstatus på 11 ulike tiltak utvalgt av direktoratene. Alle tiltakene ligger innenfor det tradisjonelle bestandsskogbruket. Tiltakene er vurdert ut fra hvordan de kan øke skogens netto CO2-opptak (karbonlagring), men for noen tiltak også betydning for andre klimagasser og for biogeofysiske effekter som albedo. Utvalget er ikke uttømmende, og også andre tiltak gjennom omløpet vil ha effekt på skogens CO2-opptak. Potensielle substitusjonseffekter gjennom tilgang på mer tømmer eller tømmer med høyere kvalitet er ikke inkludert. Klimatilpasning har vært med i vurderingen av alle tiltak. Det er korte omtaler av tiltakenes effekter på naturmangfold.

• Søgaard, Gunnhild; Allen, Micky; Astrup, Rasmus Andreas; Belbo, Helmer; Bergseng, Even & Blom, Hans H. [Vis alle 16 forfattere av denne artikkelen] (2019). Effekter av planting av skog på nye arealer. Betydning for klima, miljø og næring. NIBIO. ISSN 9788217022473. Fulltekst i vitenarkiv
• Dalsgaard, Lise; Lange, Holger & Kjønaas, O. Janne (2017). Forest soil carbon changes from measurements and models - Site-specific comparisons and implications for UNFCCC reporting. NIBIO. ISSN 9788217019350. Fulltekst i vitenarkiv Vis sammendrag

  For å verifisere beregningsmetoder og modeller for endringer av karbonlagre i skogsjord brukt i UNFCCC rapporteringen er det behov for data fra jordprøver med gjentak over tid og der prøvetakingsmetoder er konsistente. I Norge finnes ikke denne typen data på nasjonalt / landsdekkende nivå. For å møte behovet for verifisering av beregningsmetodikken brukt i UNFCCC rapporteringen innenfor rammene av eksisterende data med metodisk konsistens over tid, er det i denne undersøkelsen gjennomført ny prøvetaking av jord og vegetasjon i to etablerte forsøksfelt i skog i sør-øst Norge der vi fra før av både har data fra tidligere jordprøveanalyser og tilvekstdata for trær i skogsbestand. De to forsøksfeltene ligger på Nordmoen i Akershus (etablert 1973 og tilplantet 1974) og i Skiptvet i Østfold (etablert 1976 i eksisterende foryngelse med supplerplanting i 1977). Med nye jordprøver, biomassemålinger og vegetasjonsanalyser i 2011 gir dette to tidsserier på hhv. 38 og 34 år med hensyn på endringer i jordkarbon og inngangsverdier i beregningsmodellene. Den eksperimentelle behandlingen i Skiptvet omfatter ulik grad av treslagsblanding av bjørk og gran på de enkelte forsøksrutene, mens på Nordmoen sammenliknes rene bestand av hhv. bjørk, gran og furu. De klimatiske forhold er tilnærmet like, mens jordsmonntypen er ulik med næringsfattig sandjord på Nordmoen og næringsrik leirjord i Skiptvet. Resultatene fra forsøkene er begrenset til å representere klimatiske og vegetasjonsmessige forhold på Østlandet (og forhold tilsvarende de to lokalitetene), og forsøksfeltene er dermed ikke representative eksempelvis for kystnære og kontinentale strøk.

• Callesen, Ingeborg; Palviainen, Marjo M.; Kjønaas, O. Janne; Armolaitis, Kȩstutis E. & Rasmussen, Charlotte (2017). Soil Texture Aanalysis by Laser Diffraction – Standardisation Needed: How widespread and important is: 1) Under reporting of pretreatment method, 2) Uncertainty caused by small sample size, 3) Need for translation of old PTF’s based on sieving and sedimentation methods, 4) Lack of awareness in literature? In:J Wallinga, G Mol, VL Mulder, AM Zaal & B Jansen (red), Book of Abstracts: Soil Science in a Changing World. Wageningen Soil Conference. ISSN 9789463430616. Fulltekst i vitenarkiv Vis sammendrag

  Soil texture is a key soil physical property for soil quality and used in modeling studies through pedotransfer functions (PTF) for the prediction of physical, e.g. hydraulic, soil properties. Soil texture is quantified by a particle size distribution (PSD) of the fine earth fraction and often translated into a texture class using defined separates of clay (0 - 2 µm), silt (2 µm to 20 µm, 50 µm or 63 µm) and sand (20 µm, 50 µm or 63 µm up to 2 mm) illustrated in a texture triangle. Until now pretreatment methods (e.g. humus and carbonate removal and dispersion) followed by standardised sedimentation and sieving methods have been well-defined. From literature and a mini-survey, we know already that laser diffraction is a commonly used analytical method for soil PSD determination in scientific environmental studies that involve soils. A body of literature has documented that colloid-sized fraction results obtained by laser diffraction analysis of fine-textured soil samples are not comparable to those obtained with sedimentation and sieving methods, when translating to the traditional particle size limits clay, silt and sand. Also, operating procedures for pretreatment of soil samples are variable, and the analyzed sample volumes are small, adding to uncertainty. In this study we first compared PSD’s from three different instruments for a set of soil samples to study reproducibility using the analytical operating procedures developed by the owner institutions (Malvern Mastersizer 2000, University of Copenhagen, Coulter LS230, University of Helsinki, and Sympatec Helos, Aarhus University). Secondly, we compared the influence of 1 mm sieving and found decreased fraction standard deviation and improved repeatability of the PSD determination by laser diffraction on the Coulter LS230. 1 mm sieving should be corrected for if the mass is more than a few percent, but depending on study purpose. Thirdly, the laser diffraction PSD’s were compared with PSD’s obtained by sieving and hydrometer analysis showing well-known underestimation of colloids and fine fractions, that increased with colloid content. We conclude that PSD’s obtained by the laser diffraction method are repeatable and mostly reproducible given standardised pretreatment. Translation to texture class using traditional separates does not work well, and more work and new PTF’s for soils are needed that can translate a laser diffraction PSD into a texture class and its associated physical properties for further use in modeling studies.

• Kjønaas, O. Janne; Bárcena, Teresa G. & Hylen, Gro (2017). Effects of tree species change on forest soil carbon in Western Norway (BalanC) - preliminary results. 125th IUFRO Anniversary Congress - Book of Abstracts, 2017. Forstliche Versuchs- und Forschungsanstalt (FVA). ISSN 9783902762887. Fulltekst i vitenarkiv Vis sammendrag

  Changes in forest management have been suggested as a government policy to mitigate climate change in Norway. Tree species change is one of the major strategies considered, with the aim to increase the annual uptake of CO2 as well as the long-term storage of carbon (C) in forests. The strategy includes replacing native, deciduous species with fast-growing species, mainly Norway spruce. Forests in western Norway host some of the largest soil C pools in Scandinavia, and may potentially function as a long-term C reservoir as well as a large source of atmospheric CO2 through decomposition. The project BalanC was initiated in 2016 in order to estimate the C storage potential related to tree species in a total of 15 parallel plots of birch and planted Norway spruce at 5 locations in western Norway. In addition to estimates of C stocks in biomass and soils, we investigate soil C processes, soil fungal and earthworm diversity, albedo, and wood product life-cycles. The current presentation focuses on C stocks in soils relative to trees, soil respiration, and soil climate data. Preliminary results indicate that the soil respiration in spruce was 85 % of the respiration in birch, with a span ranging from 55-151%. The preliminary soil temperature and soil moisture data of the spruce stands were 97 and 73%, respectively, of the birch stands, indicating cooler and drier conditions under spruce which may affect decomposition and C accumulation rates. We expect C allocation in the soil to be affected by tree species, with larger C stocks in the forest floor of spruce stands compared to the mineral soil. Consistent differences in the bulk density of soils under each tree species are likely to be observed, pointing out the need to compare soil C stocks based on equal soil mass. The magnitude of the combined C stock in biomass and soil may increase with planting of spruce, however, we also expect an impact on C stability that will affect the overall mitigation effect of this measure.

• Dalsgaard, Lise; Granhus, Aksel; Søgaard, Gunnhild; Andreassen, Kjell; Børja, Isabella & Clarke, Nicholas [Vis alle 8 forfattere av denne artikkelen] (2015). Karbondynamikk ved ulike hogstformer og avvirkningsstrategier. En litteraturstudie med fokus på Oslo kommuneskog. NIBIO. Fulltekst i vitenarkiv Vis sammendrag

  Basert på en litteraturgjennomgang har vi vurdert konsekvenser av ulike hogstformer (flatehogst og lukket hogst med vekt på bledningshogst og konvertering av ensaldret skog til sjiktet skogstruktur egnet for bledning) samt forlenget omløpstid og vern med hensyn på karbonlagring og -opptak i levende biomasse, død ved og skogsjord. Med grunnlag i produksjonsmodeller og erfaringer fra langsiktige feltforsøk vurderer vi at det ikke er grunnlag for å konkludere med at det er noen vesentlig forskjell i størrelsen på karbonlageret i levende trebiomasse i bledningsskog og skog som avvirkes med flatehogst, når en legger gjennomsnittet over en tidsperiode som svarer til et normalt bestandsomløp til grunn. Det er på den annen side forskningsmessig belegg for at tilveksten over tid, og dermed årlig karbonopptak, er noe lavere i skog som behandles med bledningshogst enn i skog som forynges ved flatehogst og planting. Ved konvertering av ensaldret, ensjiktet skog til flersjiktet skog egnet for bledning vil en måtte påregne et vesentlig tilveksttap fram til fullført konvertering, noe som kan ta lang tid (50 – 100 år), og dermed redusert karbonakkumulering i den levende biomassen. Kunnskapen om hvordan konvertering fra ensjiktet til flersjiktet skogstruktur påvirker produksjonen i bestandet og karbondynamikken generelt er imidlertid mangelfull. Det fremgår av litteraturen vi har gjennomgått at når hogstinngrepet er av en betydelig størrelse, som ved flatehogst, kan det forventes et tap av total jordkarbon i tiden etter hogst i størrelsesorden 7 – 22 prosent. Det er i mange tilfeller ikke mulig å skille effekten av hogst og av markberedning på jordkarbon, men resultatene viser at et tap kan forventes også uten markberedning. Gjennom det påfølgende bestandsforløpet vil det skje en akkumulering av jordkarbon igjen, men det er usikkert hvorvidt det gjennom omløpet frem til hogstmodenhetsalder vil bygges opp igjen mer, mindre eller samme mengde som kan ha blitt tapt etter hogst. Det er sannsynlig at ulike faser av bestandsutviklingen karakteriseres av forskjellig akkumuleringshastighet, men ulike studier viser ulike resultater. Akkumuleringshastigheten kan minke med økende alder, men dette er ikke entydig vist. Det kan imidlertid ventes en fortsatt akkumulering av jordkarbon i skog som overholdes utover et normalt omløp, og i skog som vernes. Litteraturgjennomgangen i denne rapporten viser at endringsrater for jordkarbon er usikre størrelser, og samtidig sterkt påvirket av lokale faktorer. Det empiriske grunnlaget for å beskrive endringer i jordkarbon er spinkelt sett i forhold til endringer beskrevet i den levende biomasse. Dette gjør generaliseringer for jordkarbonendringer vanskelig. Hogstinngrep som tynning og lukkede hogster, inkludert små gruppehogster, gir derimot sjelden signifikante effekter på jordkarbon. Basert på dette kunne en forvente at bledning, sammenliknet med flatehogst, på lengre sikt ville medføre et høyere lager av jordkarbon ved at hogstinngrepene i liten grad påvirker jorda, i motsetning til flatehogst der det kan forventes et tap av jordkarbon i de påfølgende 10-30 år etter avvirkning. Men langsiktige observasjoner er få og gir ikke noen bakgrunn for å konkludere med dette. I den grad ulik skogbehandling vil endre treslagssammensetning og bunnvegetasjon kan det forventes en påvirkning både på akkumulering av karbon i det organiske sjikt og eventuelt også på karbonlageret i mineraljordssjiktet. Både når det gjelder tap av jordkarbon etter flatehogst og mulige effekter gjennom tynning, gruppehogst og lukket hogst kan ulike jordsmonn forventes å reagere forskjellig. En moderat forlengelse av omløpstiden utover normal hogstmodenhetsalder forventes å gi et større karbonlager i levende biomasse og jordsmonn sammenlignet med et behandlingsprogram med avvirkning ved normal hogstmodenhetsalder. Dette må samtidig avveies mot en gradvis redusert tilvekst/karbonopptak ved forlenget omløpstid i forhold til arealets maksimale produksjonsevne. Med tanke på forventet utvikling i gammel granskog kan vi si at det på nasjonal skala gjennom Landsskogtakseringen i gjennomsnitt er dokumentert et økende volum i levende biomasse, i alle fall minst 70-90 år forbi hogstmodenhetsalder på lavere og midlere boniteter (statistisk materiale foreligger ikke for eldre skog enn dette og er generelt spinklere for høye boniteter). Betydningen av forstyrrelser som vil redusere karbonlageret (skogbrann, vindfelling, insektskader med videre), vil avhenge av skala. Det vil si hvor lokal forstyrrelsen er, og om en betrakter karbonlageret i et enkelt bestand eller i all gammel skog over et større område. Per dags dato foreligger det ikke analyser som dokumenterer et totalt karbonbudsjett (inkludert jordsmonn og død ved) for gammel skog og granskog som vernes. Hyppigheten og effekten av naturlige forstyrrelser på karbonbudsjettet er også mangelfullt dokumentert. Det synes imidlertid rimelig å legge til grunn at det foregår et netto karbonopptak i granbestand som har vesentlig høyere alder enn hogstmoden skog. Hvor lenge er fremdeles et åpent spørsmål. Hovedmønsteret for utvikling av død ved i skog som avvirkes ved normal hogstmodenhetsalder er at volumet aldri blir særlig høyt. Død ved vil med andre ord være av marginal betydning for karbonakkumulering i slik forvaltet skog. Skog som får utvikle seg forbi hogstmodenhetsalder vil fortsette å bygge opp volum med levende biomasse, og mengden død ved vil øke tilsvarende gjennom naturlig avgang. I slik skog vil karbonlageret i død ved øke til et nivå som er vesentlig høyere enn i skog som avvirkes ved hogstmodenhetsalder. Dette betyr at død ved har mye større betydning for oppbygning av karbonlager i skog som får stå urørt i lang tid etter normal hogstmodenhetsalder, sammenlignet med skog som avvirkes ved hogstmodenhetsalder eller ved moderat forlenget omløpstid. Dersom et høyt karbonlager i skog prioriteres, og en samtidig ønsker å kombinere dette med høsting av virke, viser modellberegninger at disse målsetningene best kan kombineres ved å drive skogbruk med flatehogst der en øker omløpstiden noe utover normal hogstmodenhetsalder. Forlengelsen av omløpet må avveies mot noe lavere tilvekst per arealenhet, som gir et redusert opptak sett over et helt omløp, og også opp mot jordkarbonlageret som kan forventes å øke med forlenget omløpstid. I en fullstendig vurdering av den samlede klimaeffekten av ulike hogstformer og forvaltningsstrategier må en ta hensyn til tiltakets effekt på den potensielle langsiktige stabiliteten av karbonlager i biomasse og i jord. I tillegg må også hensyn til andre klimapådrivere, slik som albedo, evapotranspirasjon og BVOCs, samt effekten av substitusjon ved at trevirke kan erstatte fossile energibærere og materialer med større klimaavtrykk, inngå i vurderingen. Litteraturgjennomgangen avdekker også vesentlige kunnskapsutfordringer i forhold til å kvantifisere betydningen av de tiltakene som er vurdert på opptak og lagring av karbon i skog. Behovet for framtidig kunnskapsutvikling knyttet til karbondynamikk ved ulike hogstformer og forvaltningsstrategier er søkt belyst og oppsummeres i diskusjonskapitlet.

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