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Publications

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

2025

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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.

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Norwegian forests cover 12 million hectares and are vital for carbon uptake and biodiversity, yet CO2 absorption has declined since 2010 due to increased harvesting, mortality and reduced growth as more forests surpass harvest maturity. With 45% now economically mature and 20% older than 120 years, the future carbon uptake of these stands is uncertain, particularly if they develop towards old-growth. Old-growth forests form without stand-replacing disturbances and have diverse structures and deadwood. Norwegian mature forests mostly originate from clear-cutting, so insights from primary old-growth must be applied with caution. After maturity, forests continue to sequester carbon but more slowly, with increasing storage in deadwood and soil. Soil carbon trajectories remain uncertain: disturbance often causes short-term losses followed by decades of accumulation. Microbial communities, especially fungi, influence long-term soil carbon, but data are limited. Norway uses the Yasso soil carbon model, which predicts continued soil carbon increases with age though at slowing rates; however, it simplifies key processes, and more advanced models are in development. Biodiversity supports carbon cycling, resilience and soil health, yet knowledge gaps persist. Climate change is expected to increase disturbances, raising long-term risks for older stands. The report highlights the need for improved monitoring, research and modelling to better understand carbon dynamics and resilience as forests age.

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Key messages: Multifunctionality should serve as a guiding principle for forest governance and investment, complementing production and conservation objectives. To operationalise this vision, three guiding principles should inform EU and national policies: • Plan and manage at the landscape level balancing production, biodiversity, climate adaptation and social needs in complementary ways. Policies should support a diversity of management practices. • Align sectoral policies to ensure coherence between forestry, energy, biodiversity, climate and social objectives. • Reward and support multifunctionality explicitly through advisory programmes, certification systems, and financial mechanisms that recognise and support diverse management practices.

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As the EU intensifies its climate ambitions with the upcoming 2040 targets, it is crucial to understand how implementation of existing EU climate policies is going. How well are current policies working on the ground? Are we on track – or are there gaps that need urgent attention? As the debate around the 2040 targets heats up, this policy brief provides a timely assessment of how existing policies play out in practice and to what extent and how implementation varies across countries. Looking at Norway and Denmark, we compare the implementation of three EU regulations, which were revised in 2023: the EU Emission Trading Scheme (ETS), the Effort-Sharing Regulation (ESR) and the Land Use, Land-Use Change, and Forestry (LULUCF) sector.

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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

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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.