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Bark beetle (Ips typographus) outbreaks have the potential to damage large areas of spruce-dominated forests in Scandinavia. To define forest management strategies that will minimize the risk of bark beetle attacks, we need robust models that link forest structure and composition to the risk and potential damage of bark beetle attacks. Since data on bark beetle infestation rates and corresponding damages does not exist in Norway, we implement a previously published meta-model for estimating I. typographus damage probability and intensity. Using both current and projected climatic conditions we used the model to estimate damage inflicted by I. typographus in Norwegian spruce stands. The model produces feasible results for most of Norway’s climate and forest conditions, but a revised model tailored to Norway should be fitted to a dataset that includes older stands and lower temperatures. Based on current climate and forest conditions, the model predicts that approximately nine percent of productive forests within Norway’s main spruce-growing region will experience a loss ranging from 1.7 to 11 m3/ha of spruce over a span of five years. However, climate change is predicted to exacerbate the annual damage caused by I. typographus, potentially leading to a doubling of its detrimental effects.

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Accurate estimation of site productivity is essential for forest projections and scenario modelling. We present and evaluate models to predict site index (SI) and whether a site is productive (potential total stem volume production ≥ 1 m3·ha−1·year−1) in a wall-to-wall high-resolution (16 m × 16 m) SI map for Norway. We investigate whether remotely sensed data improve predictions. We also study the advantages and disadvantages of using boosted regression trees (BRT), a machine-learning algorithm, to create high-accuracy SI maps. We use climatic and topographical data, soil parent material, a land resource map, and depth to water, together with Sentinel-2 satellite images and airborne laser scanning metrics, as predictor variables. We use the SI observed at more than 10 000 National Forest Inventory (NFI) sample plots throughout Norway to fit BRT models and validate the models using 5822 independent temporary plots from the NFI. We benchmark our results against SI estimates from forest monitoring inventories. We find that the SI from BRT has root mean squared error (RMSE) ranging from 2.3 m (hardwoods) to 3.6 m (spruce) when tested against independent validation data from the NFI temporary plots. These RMSEs are similar or marginally better than an evaluation of SI estimates from operational forest management plans where SI normally stems from manual photo interpretation.

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The European Union (EU) set clear climate change mitigation targets to reach climate neutrality, accounting for forests and their woody biomass resources. We investigated the consequences of increased harvest demands resulting from EU climate targets. We analysed the impacts on national policy objectives for forest ecosystem services and biodiversity through empirical forest simulation and multi-objective optimization methods. We show that key European timber-producing countries – Finland, Sweden, Germany (Bavaria) – cannot fulfil the increased harvest demands linked to the ambitious 1.5°C target. Potentials for harvest increase only exists in the studied region Norway. However, focusing on EU climate targets conflicts with several national policies and causes adverse effects on multiple ecosystem services and biodiversity. We argue that the role of forests and their timber resources in achieving climate targets and societal decarbonization should not be overstated. Our study provides insight for other European countries challenged by conflicting policies and supports policymakers.

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1. Biodiversity is an important component of natural ecosystems, with higher species richness often correlating with an increase in ecosystem productivity. Yet, this relationship varies substantially across environments, typically becoming less pronounced at high levels of species richness. However, species richness alone cannot reflect all important properties of a community, including community evenness, which may mediate the relationship between biodiversity and productivity. If the evenness of a community correlates negatively with richness across forests globally, then a greater number of species may not always increase overall diversity and productivity of the system. Theoretical work and local empirical studies have shown that the effect of evenness on ecosystem functioning may be especially strong at high richness levels, yet the consistency of this remains untested at a global scale. 2. Here, we used a dataset of forests from across the globe, which includes composition, biomass accumulation and net primary productivity, to explore whether productivity correlates with community evenness and richness in a way that evenness appears to buffer the effect of richness. Specifically, we evaluated whether low levels of evenness in speciose communities correlate with the attenuation of the richness–productivity relationship. 3. We found that tree species richness and evenness are negatively correlated across forests globally, with highly speciose forests typically comprising a few dominant and many rare species. Furthermore, we found that the correlation between diversity and productivity changes with evenness: at low richness, uneven communities are more productive, while at high richness, even communities are more productive. 4. Synthesis. Collectively, these results demonstrate that evenness is an integral component of the relationship between biodiversity and productivity, and that the attenuating effect of richness on forest productivity might be partly explained by low evenness in speciose communities. Productivity generally increases with species richness, until reduced evenness limits the overall increases in community diversity. Our research suggests that evenness is a fundamental component of biodiversity–ecosystem function relationships, and is of critical importance for guiding conservation and sustainable ecosystem management decisions.

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Denne rapporten er skrevet på oppdrag fra Teknisk beregningsutvalg for klima (TBU klima). TBU klima skal ifølge mandatet gi råd om forbedringer i metoder for tiltaks- og virkemiddelanalyser på klimaområdet. I årsrapporten for 2021 har utvalget redegjort for hvilke metoder som er vurdert hittil og hvilke temaer som gjenstår. Et tema som foreløpig ikke har vært dekket av utvalget, er metoder som brukes til framskrivninger og til analyser av tiltak og virkemidler som påvirker utslipp og opptak av klimagasser fra skog, arealbruk og arealbruksendringer. Disse opptakene og utslippene rapporteres i det nasjonale klimagassregnskapet under arealbrukssektoren (eng. Land Use, Land-Use Change and Forestry, LULUCF). Formålet med denne rapporten er å gi et kunnskapsgrunnlag for utvalgets videre arbeid med vurdering av metodeapparatet som brukes til utslippsframskrivinger og analyser av tiltak og virkemidler rettet mot arealbrukssektoren, samt metode for å beregne klimaeffekt av poster på statsbudsjettet som påvirker arealbrukssektoren.

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Forests are a substantial terrestrial carbon sink, but anthropogenic changes in land use and climate have considerably reduced the scale of this system1. Remote-sensing estimates to quantify carbon losses from global forests2,3,4,5 are characterized by considerable uncertainty and we lack a comprehensive ground-sourced evaluation to benchmark these estimates. Here we combine several ground-sourced6 and satellite-derived approaches2,7,8 to evaluate the scale of the global forest carbon potential outside agricultural and urban lands. Despite regional variation, the predictions demonstrated remarkable consistency at a global scale, with only a 12% difference between the ground-sourced and satellite-derived estimates. At present, global forest carbon storage is markedly under the natural potential, with a total deficit of 226 Gt (model range = 151–363 Gt) in areas with low human footprint. Most (61%, 139 Gt C) of this potential is in areas with existing forests, in which ecosystem protection can allow forests to recover to maturity. The remaining 39% (87 Gt C) of potential lies in regions in which forests have been removed or fragmented. Although forests cannot be a substitute for emissions reductions, our results support the idea2,3,9 that the conservation, restoration and sustainable management of diverse forests offer valuable contributions to meeting global climate and biodiversity targets.

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Determining the drivers of non-native plant invasions is critical for managing native ecosystems and limiting the spread of invasive species1,2. Tree invasions in particular have been relatively overlooked, even though they have the potential to transform ecosystems and economies3,4. Here, leveraging global tree databases5,6,7, we explore how the phylogenetic and functional diversity of native tree communities, human pressure and the environment influence the establishment of non-native tree species and the subsequent invasion severity. We find that anthropogenic factors are key to predicting whether a location is invaded, but that invasion severity is underpinned by native diversity, with higher diversity predicting lower invasion severity. Temperature and precipitation emerge as strong predictors of invasion strategy, with non-native species invading successfully when they are similar to the native community in cold or dry extremes. Yet, despite the influence of these ecological forces in determining invasion strategy, we find evidence that these patterns can be obscured by human activity, with lower ecological signal in areas with higher proximity to shipping ports. Our global perspective of non-native tree invasion highlights that human drivers influence non-native tree presence, and that native phylogenetic and functional diversity have a critical role in the establishment and spread of subsequent invasions.

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Denne rapporten er del 2 av: Skogressurser i Norge - Status og framtidsscenarier. I foreliggende rapport “Skogressurser i Norge, status og framtidsscenarier for 6 regioner” presenterer vi først status for skogressursene pr. 2017 (kapittel 3-5) og historisk utvikling av ressursene (kapittel 6 og 7). Vi har undersøkt hvordan arealfordeling av bonitet og skogtyper og skogvolum og tilvekst fordeler seg på hogstklasser. I tillegg viser vi hvordan skogarealet, tilvekst og skogvolum fordeler seg på arealer der skoglovgivningen og sertifiseringsordninger krever at det må tas særskilte hensyn ved hogst (hensynsarealer, kapittel 3.2). Historisk utvikling av skogressursene er presentert for arealutviklingen for hogstklasser tilbake til år 1990, skogvolum og tilvekst tilbake til år 1925 og skogavvirkning tilbake til år 2000. I kapittel 9 og 10 presenterer vi 9 framtidsscenarier (prognoser) for mulig avvirkning/balansekvantum, tilvekst- og volumutvikling 100 år frem i tid gitt ulike forutsetninger for skogens alder ved hogst, foryngelse og ungskogpleie. I kapittel 11 vises en sammenligning av de ulike scenariene som er estimert for hver region. Oversiktene for skogressursene (referanseår 2017) og framtidsscenariene er basert på takseringer av Landsskogtakseringens permanente prøveflater for perioden 2015-2019. Prognoseverktøyet SiTree er benyttet til å estimere balansekvantum for de 9 framtidsscenariene. Vi fant at prognoser med like driftskostnader, men med varierende skogkulturinnsats, hadde relativt liten effekt på balansekvantum, men hadde effekt på treslagssammensetningen i tilgjengelig skogvolum, tilvekst og volumutvikling i produktiv skog. Varierende forutsetning om hogstalder hadde også effekt på utviklingen av skogressursene og på balansekvantumet.

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Understanding what controls global leaf type variation in trees is crucial for comprehending their role in terrestrial ecosystems, including carbon, water and nutrient dynamics. Yet our understanding of the factors influencing forest leaf types remains incomplete, leaving us uncertain about the global proportions of needle-leaved, broadleaved, evergreen and deciduous trees. To address these gaps, we conducted a global, ground-sourced assessment of forest leaf-type variation by integrating forest inventory data with comprehensive leaf form (broadleaf vs needle-leaf) and habit (evergreen vs deciduous) records. We found that global variation in leaf habit is primarily driven by isothermality and soil characteristics, while leaf form is predominantly driven by temperature. Given these relationships, we estimate that 38% of global tree individuals are needle-leaved evergreen, 29% are broadleaved evergreen, 27% are broadleaved deciduous and 5% are needle-leaved deciduous. The aboveground biomass distribution among these tree types is approximately 21% (126.4 Gt), 54% (335.7 Gt), 22% (136.2 Gt) and 3% (18.7 Gt), respectively. We further project that, depending on future emissions pathways, 17–34% of forested areas will experience climate conditions by the end of the century that currently support a different forest type, highlighting the intensification of climatic stress on existing forests. By quantifying the distribution of tree leaf types and their corresponding biomass, and identifying regions where climate change will exert greatest pressure on current leaf types, our results can help improve predictions of future terrestrial ecosystem functioning and carbon cycling.

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Forests provide a range of vital services to society and are critical habitats for biodiversity, holding inherent multifunctionality. While traditionally viewed as a byproduct of production-focused forestry, today's forest ecosystem services and biodiversity (FESB) play an essential role in several sectoral policies’ needs. Achieving policy objectives requires careful management considering the interplay of services, influenced by regional aspects and climate. Here, we examined the multifunctionality gap caused by these factors through simulation of forest management and multi-objective optimization methods across different regions - Finland, Norway, Sweden and Germany (Bavaria). To accomplish this, we tested diverse management regimes (productivity-oriented silviculture, several continuous cover forestry regimes and set asides), two climate scenarios (current and RCP 4.5) and three policy strategies (National Forest, Biodiversity and Bioeconomy Strategies). For each combination we calculated a multifunctionality metric at the landscape scale based on 5 FESB classes (biodiversity conservation, bioenergy, climate regulation, wood, water and recreation). In Germany and Norway, maximum multifunctionality was achieved by increasing the proportion of set-asides and proportionally decreasing the rest of management regimes. In Finland, maximum MF would instead require that policies address greater diversity in management, while in Sweden, the pattern was slightly different but similar to Finland. Regarding the climate scenarios, we observed that only for Sweden the difference in the provision of FESB was significant. Finally, the highest overall potential multifunctionality was observed for Sweden (National Forest scenario, with a value of 0.94 for the normalized multifunctionality metric), followed by Germany (National Forest scenario, 0.83), Finland (Bioeconomy scenario, 0.81) and Norway (National Forest scenario, 0.71). The results highlight the challenges of maximizing multifunctionality and underscore the significant influence of country-specific policies and climate change on forest management. To achieve the highest multifunctionality, strategies must be tailored to specific national landscapes, acknowledging both synergistic and conflicting FESB.

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Forests provide a range of vital services to society and are critical habitats for biodiversity, holding inherent multifunctionality. While traditionally viewed as a byproduct of production-focused forestry, today's forest ecosystem services and biodiversity (FESB) play an essential role in several sectoral policies’ needs. Achieving policy objectives requires careful management considering the interplay of services, influenced by regional aspects and climate. Here, we examined the multifunctionality gap caused by these factors through simulation of forest management and multi-objective optimization methods across different regions - Finland, Norway, Sweden and Germany (Bavaria). To accomplish this, we tested diverse management regimes (productivity-oriented silviculture, several continuous cover forestry regimes and set asides), two climate scenarios (current and RCP 4.5) and three policy strategies (National Forest, Biodiversity and Bioeconomy Strategies). For each combination we calculated a multifunctionality metric at the landscape scale based on 5 FESB classes (biodiversity conservation, bioenergy, climate regulation, wood, water and recreation). In Germany and Norway, maximum multifunctionality was achieved by increasing the proportion of set-asides and proportionally decreasing the rest of management regimes. In Finland, maximum MF would instead require that policies address greater diversity in management, while in Sweden, the pattern was slightly different but similar to Finland. Regarding the climate scenarios, we observed that only for Sweden the difference in the provision of FESB was significant. Finally, the highest overall potential multifunctionality was observed for Sweden (National Forest scenario, with a value of 0.94 for the normalized multifunctionality metric), followed by Germany (National Forest scenario, 0.83), Finland (Bioeconomy scenario, 0.81) and Norway (National Forest scenario, 0.71). The results highlight the challenges of maximizing multifunctionality and underscore the significant influence of country-specific policies and climate change on forest management. To achieve the highest multifunctionality, strategies must be tailored to specific national landscapes, acknowledging both synergistic and conflicting FESB.

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Management of Scots pine (Pinus sylvestris L.) in Norway requires a forest growth and yield model suitable for describing stand dynamics of even-aged forests under contemporary climatic conditions with and without the effects of silvicultural thinning. A system of equations forming such a stand-level growth and yield model fitted to long-term experimental data is presented here. The growth and yield model consists of component equations for (i) dominant height, (ii) stem density (number of stems per hectare), (iii) total basal area, (iv) and total stem volume fitted simultaneously using seemingly unrelated regression. The component equations for stem density, basal area, and volume include a thinning modifier to forecast stand dynamics in thinned stands. It was shown that thinning significantly increased basal area and volume growth while reducing competition related mortality. No significant effect of thinning was found on dominant height. Model examination by means of various fit statistics indicated no obvious bias and improvement in prediction accuracy in comparison to existing models in general. An application of the developed stand-level model comparing different management scenarios exhibited plausible long-term behavior and we propose this is therefore suitable for national deployment.

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The latitudinal diversity gradient (LDG) is one of the most recognized global patterns of species richness exhibited across a wide range of taxa. Numerous hypotheses have been proposed in the past two centuries to explain LDG, but rigorous tests of the drivers of LDGs have been limited by a lack of high-quality global species richness data. Here we produce a high-resolution (0.025° × 0.025°) map of local tree species richness using a global forest inventory database with individual tree information and local biophysical characteristics from ~1.3 million sample plots. We then quantify drivers of local tree species richness patterns across latitudes. Generally, annual mean temperature was a dominant predictor of tree species richness, which is most consistent with the metabolic theory of biodiversity (MTB). However, MTB underestimated LDG in the tropics, where high species richness was also moderated by topographic, soil and anthropogenic factors operating at local scales. Given that local landscape variables operate synergistically with bioclimatic factors in shaping the global LDG pattern, we suggest that MTB be extended to account for co-limitation by subordinate drivers.

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The preservation of the functionality of forest soil is a key aspect in planning mechanized harvesting operations. Therefore, knowledge and information about stand and soil characteristics are vital to the planning process. In this respect, depth-to-water (DTW) maps were reviewed with regard to their potential use as a prediction tool for wheel ruts. To test the applicability of open source DTW maps for prediction of rutting, the ground surface conditions of 20 clear-cut sites were recorded post harvesting, using an unmanned aerial vehicle (UAV). In total, 80 km of machine tracks were categorized by the severity of occurring rut-formations to investigate whether: i) operators intuitively avoid areas with low DTW values, ii) a correlation exists between decreasing DTW values and increasing rut severity, and iii) DTW maps can serve as reliable decision-making tool in minimizing the environmental effects of big machinery deployment. While the machine operators did not have access to these predictions (DTW maps) during the operations, there was no visual evidence that driving through these areas was actively avoided, resulting in a higher density of severe rutting within areas with DTW values <1 m. A logistic regression analysis confirmed that the probability of severe rutting rapidly increases with decreasing DTW values. However, significant differences between sites exist which might be attributed to a series of other factors such as soil type, weather conditions, number of passes and load capacity. Monitoring these factors is hence highly recommended in any further follow-up studies on soil trafficability.

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Arealbrukssektoren (engelsk: Land Use, Land-Use Change and Forestry, LULUCF) omfatter arealbruk og arealbruksendringer, med tilhørende utslipp og opptak av CO2, CH4 og N2O, og er en del av det nasjonale klimagassregnskapet under FNs klimakonvensjon. Framskrivningene presentert her er basert på data og metodikk fra Norges siste rapportering til FNs klimakonvensjon (IPCC), Norges National Inventory Report (NIR), innsendt 8. april 2022 (Miljødirektoratet mfl. 2022). Perioden 2006 – 2020 har vært lagt til grunn som referanseperiode, og framskrivning av arealutvikling og utslipp er i all hovedsak basert på rapporterte data for denne tidsperioden. Utviklingen i gjenværende skog er framskrevet ved hjelp av simuleringsverktøyet SiTree og Yasso07. Klimaendringer under klimascenariet i RCP 4.5 er lagt til grunn. Framskrivingen er framstilt på to ulike formater: Både i henhold til FNs klimakonvensjon sitt regelverk (alle arealbrukskategorier og kilder) og basert på EUs regelverk under LULUCF-forordningen (2018/841) (European Union 2018).

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To mitigate climate change, several European countries have launched policies to promote the development of a renewable resource-based bioeconomy. These bioeconomy strategies plan to use renewable biological resources, which will increase timber and biomass demands and will potentially conflict with multiple other ecosystem services provided by forests. In addition, these forest ecosystem services (FES) are also influenced by other, different, policy strategies, causing a potential mismatch in proposed management solutions for achieving the different policy goals. We evaluated how Norwegian forests can meet the projected wood and biomass demands from the international market for achieving mitigation targets and at the same time meet nationally determined targets for other FES. Using data from the Norwegian national forest inventory (NFI) we simulated the development of Norwegian forests under different management regimes and defined different forest policy scenarios, according to the most relevant forest policies in Norway: national forest policy (NFS), biodiversity policy (BIOS), and bioeconomy policy (BIES). Finally, through multi-objective optimization, we identified the combination of management regimes matching best with each policy scenario. The results for all scenarios indicated that Norway will be able to satisfy wood demands of up to 17 million m3 in 2093. However, the policy objectives for FES under each scenario caused substantial differences in terms of the management regimes selected. We observed that BIES and NFS resulted in very similar forest management programs in Norway, with a dominance of extensive management regimes. In BIOS there was an increase of set aside areas and continuous cover forestry, which made it more compatible with biodiversity indicators. We also found multiple synergies and trade-offs between the FES, likely influenced by the definition of the policy targets at the national scale.

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It is expected that European Boreal and Temperate forests will be greatly affected by climate change, causing natural disturbances to increase in frequency and severity. To detangle how, through forest management, we can make forests less vulnerable to the impact of natural disturbances, we need to include the risks of such disturbances in our decision-making tools. The present review investigates: i) how the most important forestry-related natural disturbances are linked to climate change, and ii) different modelling approaches that assess the risks of natural disturbances and their applicability for large-scale forest management planning. Global warming will decrease frozen soil periods, which increases root rot, snow, ice and wind damage, cascading into an increment of bark beetle damage. Central Europe will experience a decrease in precipitation and increase in temperature, which lowers tree defenses against bark beetles and increases root rot infestations. Ice and wet snow damages are expected to increase in Northern Boreal forests, and to reduce in Temperate and Southern Boreal forests. However, lack of snow cover may increase cases of frost-damaged seedlings. The increased temperatures and drought periods, together with a fuel increment from other disturbances, likely enhance wildfire risk, especially for Temperate forests. For the review of European modelling approaches, thirty-nine disturbance models were assessed and categorized according to their required input variables and to the models’ outputs. Probability models are usually common for all disturbance model approaches, however, models that predict disturbance effects seem to be scarce.

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SiTree is a flexible, cross-platform, open-source framework for individual-tree simulators intended to facilitate accurate and flexible analyses of forest growth and yield, or more generally forest dynamics simulations. SiTree provides generic functionality to build customized individual-tree simulators using additional user-written code. In the forestry literature there are a wide variety of individual models that describe the different parts of forest growth and dynamics and new models are continuously developed and published. The aim of SiTree is to provide a broad community of R-users within forestry with an easily adaptable individual-tree simulator framework and an easily accessible tool for testing and combining new and existing models describing parts of forest growth dynamics.

Sammendrag

Vi gir i den første delen av denne rapporten en oversikt over dagens skogressurser i Norge og den historiske utviklingen tilbake til 1990. Oversiktene er basert på data fra Landsskogtakseringens permanente prøveflater. Vi presenterer arealfordeling av bonitet og skogtyper i ulike hogstklasser, skogvolum og tilvekst, aldersutviklingen i skog, historisk avvirkning, samt omfang av sluttavvirkning i yngre skog de senere årene, her definert som skog som er yngre enn nedre aldersgrense for hogstklasse 5. Vi dokumenterer også hvor stor andel av skogressursene som står på arealer der det etter sertifiseringsordninger og skoglovgivningen må tas særskilte hensyn ved hogst. I tillegg har vi analysert omfanget av hogst i yngre skog, og som her er definert som avvirkning i skog som er yngre enn nedre aldersgrense for hogstklasse 5. I andre halvdel av rapporten presenterer vi 14 forskjellige prognoser for balansekvantum, med ulike forutsetninger med hensyn til økonomisk drivverdig areal (basert på driftskostnad), skogkulturinnsats, nedre alder ved sluttavvirkning, og for alternative scenarier for prioritering av arealer ved økning av vern av skog. Varierende skogkulturinnsats hadde relativt liten effekt på balansekvantum, men større effekt på tilvekst og volumutvikling samt sammensetningen av framtidig hogstkvantum og skogvolum per treslagsgruppe (gran, furu, lauvtrær). Varierende forutsetninger om nedre aldersgrense for sluttavvirkning hadde også effekt på utviklingen av ressursene og på balansekvantumet. Prognosene der inntil 25 prosent av hogstkvantumet fra sluttavvirkning kan hentes i hogstklasse 4 og resten i hogstklasse 5 gav et høyere balansekvantum enn i prognosene der sluttavvirkning tidligst kan gjennomføres når skogen når nedre aldersgrense for hogstklasse 5. Prognosene uten hogst i hogstklasse 4 gav imidlertid som resultat en større oppbygning av stående volum og tilvekst over tid....

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Stand-level growth and yield models are important tools that support forest managers and policymakers. We used recent data from the Norwegian National Forest Inventory to develop stand-level models, with components for dominant height, survival (number of survived trees), ingrowth (number of recruited trees), basal area, and total volume, that can predict long-term stand dynamics (i.e. 150 years) for the main species in Norway, namely Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.), and birch (Betula pubescens Ehrh. and Betula pendula Roth). The data used represent the structurally heterogeneous forests found throughout Norway with a wide range of ages, tree size mixtures, and management intensities. This represents an important alternative to the use of dedicated and closely monitored long-term experiments established in single species even-aged forests for the purpose of building these stand-level models. Model examination by means of various fit statistics indicated that the models were unbiased, performed well within the data range and extrapolated to biologically plausible patterns. The proposed models have great potential to form the foundation for more sophisticated models, in which the influence of other factors such as natural disturbances, stand structure including species mixtures, and management practices can be included.

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Forest harvest residue is a low-competitive biomass feedstock that is usually left to decay on site after forestry operations. Its removal and pyrolytic conversion to biochar is seen as an opportunity to reduce terrestrial CO2 emissions and mitigate climate change. The mitigation effect of biochar is, however, ultimately dependent on the availability of the biomass feedstock, thus CO2 removal of biochar needs to be assessed in relation to the capacity to supply biochar systems with biomass feedstocks over prolonged time scales, relevant for climate mitigation. In the present study we used an assembly of empirical models to forecast the effects of harvest residue removal on soil C storage and the technical capacity of biochar to mitigate national-scale emissions over the century, using Norway as a case study for boreal conditions. We estimate the mitigation potential to vary between 0.41 and 0.78 Tg CO2 equivalents yr−1, of which 79% could be attributed to increased soil C stock, and 21% to the coproduction of bioenergy. These values correspond to 9–17% of the emissions of the Norwegian agricultural sector and to 0.8–1.5% of the total national emission. This illustrates that deployment of biochar from forest harvest residues in countries with a large forestry sector, relative to economy and population size, is likely to have a relatively small contribution to national emission reduction targets but may have a large effect on agricultural emission and commitments. Strategies for biochar deployment need to consider that biochar's mitigation effect is limited by the feedstock supply which needs to be critically assessed.

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Statskog eier om lag 8% av Norges produktive skogareal. Skogen er dominert av en stor andel hogstmoden skog og en overvekt av skog på lavere boniteter. Tilveksten i skogen er svakt avtagende noe som sannsynligvis skyldes skjev aldersklasse fordeling med mye eldre skog. Hogsten i skogen er kun om lag en tredjedel av tilveksten og fører til en sterk oppbygging av det stående volum på Statskog sine eiendommer. Når tilveksten er høyere enn avvirking vil man vanligvis forvente et opptak av karbon i skogen. Dette er også tilfellet for Statskog hvor det er estimert et karbonopptak på om lag 1,5 mill. ton CO2 per år. Karbon opptaket er litt mindre nå enn det var tidligere ettersom tilveksten er fallende og hogsten har vært svakt økende. Når man driver hogst er det fossile utslipp knyttet til hogst, terrengtransport, og tømmerbil transport. Mellom 2010 og 2019 har utslippene fra hogst og transport variert mellom 1 600 tonn CO2 og 4 900 tonn CO2 avhengig av hogstkvantum. Det er viktig å fremheve at utslippene fra transport og hogst er minimale sammenlignet med opptaket av CO2 i skogen til Statskog. Når man avvirker skog produseres det materialer som kan erstatte fossil intensive materialer til andre sektorer slik som bygg og energi. Det er vanskelig å direkte kvantifisere substitusjonen av fossil intensive materialer da effekten er avhengig av de spesifikke materialene som erstattes og effektiviteten i hele verdikjeden. På den andre siden er substitusjon en viktig del av klimaeffekten ved hogst og bør inkluderes når man vurderer klimaeffekter av skogsdrift. Hvis vi antar at skurlast produsert fra avvirkningen til Statskog benyttes til å erstatte stål er det estimert at substitusjonen mellom 2010 og 2019 har variert mellom 32 000 og 99 000 tonn CO2 per år. Substitusjonseffekten er dermed mye høyere enn utslippene fra hogst og transport, men likevel små i forhold til opptaket av karbon i skogen til Statskog. Gjennom skogbehandlingen kan man kraftig påvirke opptaket av karbon i skogen. På lang sikt, er det muligheter for å øke opptaket av karbon gjennom økt plantetetthet og økt bruk av foredlet plantemateriale. Ved å gjødsle skogen kan man oppnå raskt økende opptak av karbon, men den samlede effekten er ikke nødvendigvis så stor da det er begrenset med arealer som er egnet til økt gjødslingsintensitet. Andre tiltak slik som forlenget omløpstid kan også vurderes, men må ses i sammenheng med skogens helsetilstand og effekter på det tilgjengelige hogstkvantum.

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I denne rapporten gis en oversikt over skogressursene i Innlandet basert på Landsskogtakseringens takseringer av permanente prøveflater i fylket i perioden 2015-2019 (referanseår 2017), og utviklingstrekk for skogressursene i fylket siste 10 år (2007-2017). Etter ønske fra oppdragsgiver har vi også utarbeidet oversikter over skogressursene i vernskog, omfanget av hogst i yngre skog (her definert som avvirkning i hogstklasse 4 eller yngre), og beregnet hvor stor produksjonsøkning (årlig middeltilvekst) en kan forvente ved treslagskifte på lauvtredominerte arealer i fjellskogen. Videre er det beregnet hvor mye areal i hogstklasse 2 som har behov for ungskogpleie. I siste del av rapporten presenteres prognoser for balansekvantum med ulike forutsetninger med hensyn på tellende areal (basert på driftskostnad), skogkulturinnsats og nedre alder ved sluttavvirkning. I de fleste prognosene har vi forutsatt at inntil 25 prosent av hogstuttaket (volum) fra sluttavvirkning av gran tas ut i hogstklasse 4, en fordeling som ligger tett opptil dagens praksis. For å kunne si noe om de langsiktige konsekvensene av tidlig hogst er det også utviklet et sett prognoser der nedre alder for sluttavirkning er satt lik nedre aldersgrense for hogstklasse 5.....

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Forest structural properties largely govern surface fluxes of moisture, energy, and momentum that strongly affect regional climate and hydrology. Forest structural properties are greatly shaped by forest management activities, especially in the Fennoscandia (Norway, Sweden, and Finland). Insight into transient developments in forest structure in response to management intervention is therefore essential to understanding the role of forest management in mitigating regional climate change. The aim of this study is to present a simple grid-based framework – the Fennoscandic Forest State Simulator (F2S2) -- for predicting time-dependent forest structural trajectories in a manner compatible with land models employed in offline or asynchronously coupled climate and hydrological research. F2S2 enables the prescription of future regional forest structure as a function of: i) exogenously defined scenarios of forest harvest intensity; ii) forest management intensity; iii) climate forcing. We demonstrate its application when applied as a stand-alone tool for forecasting three alternative future forest states in Norway that differ with respect to background climate forcing, forest harvest intensity (linked to two Shared Socio-economic Pathways (SSPs)), and forest management intensity. F2S2 captures impacts of climate forcing and forest management on general trends in forest structural development over time, and while climate is the main driver of longer-term forest structural dynamics, the role of harvests and other management-driven effects cannot be overlooked. To our knowledge this is the first paper presenting a method to map forest structure in space and time in a way that is compatible with land surface or hydrological models employing sub-grid tiling.

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A new stand-level growth and yield model, consisting of component equations for stand volume, basal area, survival, and dominant stand height, was developed from a dataset of long-term trials for managed thinned and unthinned even-aged Norway spruce (Picea abies (L.) Karst.) forests in Norway. The developed models predict considerably faster growth rates than the existing Norwegian models. Further, it was found that the existing Norwegian stand-level models do not match the data from the thinning trails. The significance of thinning response functions indicated that thinning increases basal area growth while reducing competition related mortality. No significant effects of thinning were found in the dominant stand height growth. Model examination by means of cross-validation indicated that the models were unbiased and performed well within the data range. An application of the developed stand-level model highlights the potential use for these models in comparing different management scenarios.

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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.

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Skogen i Norge har et årlig netto opptak i underkant av 30 mill. tonn CO2. Størrelsen på opptaket påvirkes av forvaltningen av skogarealene, både gjennom endringer i totalarealet (avskoging og påskoging), og forvaltningen av de eksisterende skogarealene. I denne rapporten presenteres en første vurdering av syv klimatiltak som ikke tidligere er utredet, en kunnskapsoppdatering av noen tidligere utredede klimatiltak, og en framskrivning av mulige effekter på netto CO2-opptak av ulike nivå på implementerte tiltak. Rapporten er skrevet på bestilling fra Landbruksdirektoratet og Miljødirektoratet, og det er direktoratene som har gjort utvalget av tiltak....

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Det årlige netto opptaket i skogen i Norge økte frem til 2009 (over 35 mill. tonn), og har etter det vist en avtakende trend. I 2018 var det et netto opptak på i underkant av 28 millioner tonn CO2- ekvivalenter. Størrelsen på opptaket påvirkes av forvaltningen av skogarealene, både gjennom endringer i totalarealet (avskoging og påskoging), og forvaltningen av de eksisterende skogarealene. I en første rapport til Klimakur 2030 – skrevet på oppdrag fra Miljødirektorat og Landbruksdirektoratet - ble det presentert en første vurdering av syv klimatiltak som ikke tidligere var utredet, samt en kunnskapsoppdatering for noen tidligere utredede klimatiltak. I denne rapporten presenteres ytterligere vurderinger av fire av disse tiltakene; ungskogpleie, grøfterensk, stubbebehandling mot råte og gjødsling med treaske. Rapporten er skrevet på bestilling fra Landbruks- og matdepartementet (LMD) og Klima- og miljødepartementet (KLD), og det er departementene som har gjort utvalget av tiltak som skulle vurderes videre...

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Late-spring frosts (LSFs) affect the performance of plants and animals across the world’s temperate and boreal zones, but despite their ecological and economic impact on agriculture and forestry, the geographic distribution and evolutionary impact of these frost events are poorly understood. Here, we analyze LSFs between 1959 and 2017 and the resistance strategies of Northern Hemisphere woody species to infer trees’ adaptations for minimizing frost damage to their leaves and to forecast forest vulnerability under the ongoing changes in frost frequencies. Trait values on leaf-out and leaf-freezing resistance come from up to 1,500 temperate and boreal woody species cultivated in common gardens. We find that areas in which LSFs are common, such as eastern North America, harbor tree species with cautious (late-leafing) leaf-out strategies. Areas in which LSFs used to be unlikely, such as broad-leaved forests and shrublands in Europe and Asia, instead harbor opportunistic tree species (quickly reacting to warming air temperatures). LSFs in the latter regions are currently increasing, and given species’ innate resistance strategies, we estimate that ∼35% of the European and ∼26% of the Asian temperate forest area, but only ∼10% of the North American, will experience increasing late-frost damage in the future. Our findings reveal region-specific changes in the spring-frost risk that can inform decision-making in land management, forestry, agriculture, and insurance policy.

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New mortality models were developed for the purpose of improving long-term growth and yield simulations in Finland, Norway, and Sweden and were based on permanent national forest inventory plots from Sweden and Norway. Mortality was modelled in two steps. The first model predicts the probability of survival, while the second model predicts the proportion of basal area in surviving trees for plots where mortality has occurred. In both models, the logistic function was used. The models incorporate the variation in prediction period length and in plot size. Validation of both models indicated unbiased mortality rates with respect to various stand characteristics such as stand density, average tree diameter, stand age, and the proportion of different tree species, Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) Karst.), and broadleaves. When testing against an independent dataset of unmanaged spruce-dominated stands in Finland, the models provided unbiased prediction with respect to stand age.

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An understanding of the relationship between volume increment and stand density (basal area, stand density index, etc.) is of utmost importance for properly managing stand density to achieve specific management objectives. There are two main approaches to analyse growth–density relationships. The first relates volume increment to stand density through a basic relationship, which can vary with site productivity, age, and potentially incorporates treatment effects. The second is to relate the volume increment and density of thinned experimental plots relative to that of an unthinned experimental plot on the same site. Using a dataset of 229 thinned and unthinned experimental plots of Norway spruce, a growth model is developed describing the relationship between gross or net volume increment and basal area. The models indicate that gross volume increases with increasing basal area up to 50 m2 and thereafter becomes constant out to the maximum basal area. Alternatively, net volume increment was maximized at a basal area of 43 m2 and decreased with further increases in basal area. However, the models indicated a wide range where net volume increment was essentially constant, varying by less than 1 m3 ha−1 year−1. An analysis of different thinning scenarios indicated that the relative relationship between volume increment and stand density was dynamic and changed over the course of a rotation.

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I denne rapporten presenteres resultater fra prognosekjøringer der vi har beregnet poensiell virkestilgang for et område avgrenset til fylkene Rogaland, Hordaland og Sogn og Fjordane, med utgangspunkt i data registrert på Landsskogtakseringens permanente prøvflater i perioden 2013-2017. Prognosene er kjørt for en periode på 100 år og omfatter gran- og furudominert skog på bonitet 11 og høyere. Prognoser er utarbeidet for seks alternativ (Alt. 1-6) der det er lagt til grunn varierende forutsetninger med hensyn til hogsttidspunkt og skogkultur: Alt. 1: Avvirkning ved nedre alderssgrense for hogstklasse V. Tilplanting med gran på 100 % av granskogarealene som avvirkes. Ikke treslagsskifte i furuskog. Alt. 2: Avvirkning 10 år før nedre aldersgrense for hogstklasse V. Tilplanting med gran på 100 % av granskogarealene som avvirkes. Ikke treslagsskifte i furuskog. Alt. 3: Avvirkning 10 år etter nedre aldersgrense for hogstklasse V. Tilplanting med gran på 100 % av granskogarealene som avvirkes. Ikke treslagsskifte i furuskog. Alt. 4: Avvirkning ved nedre alderssgrense for hogstklasse V. Tilplanting med gran på 100 % av granskogarealene som avvirkes. Treslagskifte til gran på 50 % av hogstarealet i furuskog. Alt. 5: Avvirkning ved nedre alderssgrense for hogstklasse V. Tilplanting med gran på 70 % av granskogarealene som avvirkes. Treslagskifte til gran på 50 % av hogstarealet i furuskog. Alt. 6: Avvirkning ved nedre alderssgrense for hogstklasse V. Tilplanting med gran på 50 % av granskogarealene som avvirkes. Treslagskifte til gran på 10 % av hogstarealet i furuskog...

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The identity of the dominant root-associated microbial symbionts in a forest determines the ability of trees to access limiting nutrients from atmospheric or soil pools1,2, sequester carbon3,4 and withstand the effects of climate change5,6. Characterizing the global distribution of these symbioses and identifying the factors that control this distribution are thus integral to understanding the present and future functioning of forest ecosystems. Here we generate a spatially explicit global map of the symbiotic status of forests, using a database of over 1.1 million forest inventory plots that collectively contain over 28,000 tree species. Our analyses indicate that climate variables—in particular, climatically controlled variation in the rate of decomposition—are the primary drivers of the global distribution of major symbioses. We estimate that ectomycorrhizal trees, which represent only 2% of all plant species7, constitute approximately 60% of tree stems on Earth. Ectomycorrhizal symbiosis dominates forests in which seasonally cold and dry climates inhibit decomposition, and is the predominant form of symbiosis at high latitudes and elevation. By contrast, arbuscular mycorrhizal trees dominate in aseasonal, warm tropical forests, and occur with ectomycorrhizal trees in temperate biomes in which seasonally warm-and-wet climates enhance decomposition. Continental transitions between forests dominated by ectomycorrhizal or arbuscular mycorrhizal trees occur relatively abruptly along climate-driven decomposition gradients; these transitions are probably caused by positive feedback effects between plants and microorganisms. Symbiotic nitrogen fixers—which are insensitive to climatic controls on decomposition (compared with mycorrhizal fungi)—are most abundant in arid biomes with alkaline soils and high maximum temperatures. The climatically driven global symbiosis gradient that we document provides a spatially explicit quantitative understanding of microbial symbioses at the global scale, and demonstrates the critical role of microbial mutualisms in shaping the distribution of plant species.

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I denne rapporten presenteres framskrivninger for opptak og utslipp fra arealbrukssektoren (eng. Land Use, Land-Use Change and Forestry; LULUCF) frem til 2100. Framskrivninger av opptak og utslipp av CO2 og andre klimagasser fra arealbrukssektoren er utført i tråd med metodikken brukt i klimagassregnskapet for Norge i 2019 (Miljødirektoratet mfl. 2019), og basert på data rapportert for 2010 – 2017 som referanseperiode. Framskrivningen for opptak og utslipp i skog er basert på tilsvarende metodikk som i referansebanen for forvaltede skogarealer (eng. Forest Reference Level, FRL), som publisert i National Forest Accounting Plan (Klima- og miljødepartementet 2019), men basert på nyeste tilgjengelige data og med implementert politikk. Framskrivningene er utført basert på rapporteringen under FNs klimakonvensjon og Kyotoprotokollen, samt EUs LULUCF-forordning.

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• Key message A dataset of forest resource projections in 23 European countries to 2040 has been prepared for forest-related policy analysis and decision-making. Due to applying harmonised definitions, while maintaining country-specific forestry practices, the projections should be usable from national to international levels. The dataset can be accessed at https://doi.org/10.5061/dryad.4t880qh . The associated metadata are available at https://metadata-afs.nancy.inra.fr/geonetwork/srv/eng/catalog.search#/metadata/8f93e0d6-b524-43bd-bdb8-621ad5ae6fa9 .

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The present study aims to develop biologically sound and parsimonious site index models for Norway to predict changes in site index (SI) under different climatic conditions. The models are constructed using data from the Norwegian National Forest Inventory and climate data from the Norwegian meteorological institute. Site index was modeled using the potential modifier functional form, with a potential component (POT) depending on site quality classes and two modifier components (MOD): temperature and moisture. Each of these modifiers was based on a portfolio of candidate variables. The best model for spruce-dominated stands included temperature as modifier (R2 = 0.56). In the case of pine- and deciduous-dominated stands, the best models included both modifiers (R2 = 0.40 and 0.54 for temperature and moisture, respectively). We illustrate the use of the models by analyzing the possible shift in SI for year 2100 under one (RCP4.5) of the benchmark scenarios adopted by the Intergovernmental Panel on Climate Change for its fifth assessment report. The models presented can be valuable for evaluating the effect of climate change scenarios in Norwegian forests.

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Boreal forests contain 30% of the global forest carbon with the majority residing in soils. While challenging to quantify, soil carbon changes comprise a significant, and potentially increasing, part of the terrestrial carbon cycle. Thus, their estimation is important when designing forest-based climate change mitigation strategies and soil carbon change estimates are required for the reporting of greenhouse gas emissions. Organic matter decomposition varies with climate in complex nonlinear ways, rendering data aggregation nontrivial. Here, we explored the effects of temporal and spatial aggregation of climatic and litter input data on regional estimates of soil organic carbon stocks and changes for upland forests. We used the soil carbon and decomposition model Yasso07 with input from the Norwegian National Forest Inventory (11275 plots, 1960–2012). Estimates were produced at three spatial and three temporal scales. Results showed that a national level average soil carbon stock estimate varied by 10% depending on the applied spatial and temporal scale of aggregation. Higher stocks were found when applying plot-level input compared to country-level input and when long-term climate was used as compared to annual or 5-year mean values. A national level estimate for soil carbon change was similar across spatial scales, but was considerably (60–70%) lower when applying annual or 5-year mean climate compared to long-term mean climate reflecting the recent climatic changes in Norway. This was particularly evident for the forest-dominated districts in the southeastern and central parts of Norway and in the far north. We concluded that the sensitivity of model estimates to spatial aggregation will depend on the region of interest. Further, that using long-term climate averages during periods with strong climatic trends results in large differences in soil carbon estimates. The largest differences in this study were observed in central and northern regions with strongly increasing temperatures.

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Key Message. This analysis of the tools and methods currently in use for reporting woody biomass availability in 21 European countries has shown that most countries use, or are developing, National Forest Inventory-oriented models whereas the others use standwise forest inventory--oriented methods. Context. Knowledge of realistic and sustainable wood availability in Europe is highly relevant to define climate change mitigation strategies at national and European level, to support the development of realistic targets for increased use of renewable energy sources and of industry wood. Future scenarios at European level highlight a deficit of domestic wood supply compared to wood consumption, and some European countries state they are harvesting above the increment. Aims. Several country-level studies on wood availability have been performed for international reporting. However, it remains essential to improve the knowledge on the projection methods used across Europe to better evaluate forecasts. Methods. Analysis was based on descriptions supplied by the national correspondentsinvolved in USEWOOD COST Action (FP1001), and further enriched with additionaldata from international reports that allowedcharacterisation of the forests in these countries for the same base year. Results. Methods currently used for projecting wood availability were described for 21 European countries. Projection systems based on National Forest Inventory (NFI) data prevail over methods based on forest management plans. Only a few countries lack nationwide projection tools, still using tools developed for specific areas. Conclusions. A wide range of NFI-based systems for projecting wood availability exists, being under permanent improvement. The validation of projection forecasts and the inclusion of climate sensitive growth models into these tools are common aims for most countries. Cooperation among countries would result in higher efficiency when developing and improving projection tools and better comparability among them.

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Framskrivninger av opptak og utslipp av CO2 og andre klimagasser fra skog og andre landarealer (LULUCF-sektoren) fram til 2120, utført i tråd med metodikken brukt i klimagassregnskapet for Norge i 2014 (Miljødirektoratet mfl. 2014), presenteres i denne rapporten. Framskrivingene er basert på tre ulike scenarier for fremtidig klima: • Dagens klima. • 2-gradersmålet, det vil si en global temperaturøkning som flater ut på to grader i 2100 (”oppfyller” 2-gradersmålet). Her er RCP 2.6 lagt til grunn. • Business-as-usual, det vil si forventet klimaendring dersom nye tiltak ikke gjennomføres. Her er RCP 8.5 lagt til grunn. iii En videreføring av dagens politikk og virkemiddelbruk er lagt til grunn for framskrivningene. Videre legges til grunn en sannsynlig utvikling for avvirkning ut fra hogstmodenhet og tilgjengelighet av tømmer i norske skoger (Antón Fernández og Astrup 2012). Skog er den viktigste arealkategorien for opptak av klimagasser, med et netto opptak på 30 741 Gg CO2-ekvivalenter i 2012 (Miljødirektoratet mfl. 2014). Framskrivningene viser at skog også i fremtiden vil være den viktigste arealkategorien for opptak av klimagasser, men opptaket vil reduseres betydelig over de nærmeste 100 år. Dette vil skje uavhengig av klimascenario, og skyldes en kombinasjon av økende avvirkning og endring av skogens alderssammensetning. Den skogen som ble plantet i tiårene etter 2. verdenskrig begynner nå å bli hogstmoden, og det vil være et betydelig volum i skog som vil bli hogstmoden de kommende 30 år (Granhus mfl. 2014). Det gir større arealer med hogstmoden skog nær vei, og denne skogen har også større volum per arealenhet enn eldre hogstmoden skog. Dette vil gi økt avvirkning, og dermed høyere utslipp (ettersom all avvirkning regnes som utslipp ved avvirkningstidspunktet i klimagassregnskapet). Skogen i Norge har i dag en ujevn alderssammensetning, med en stor andel av arealet i de mest produktive faser (høy tilvekst, som gir høyt opptak). Med fortsatt forvaltning som i dag vil alderssammensetningen langsomt bli mer jevn, og vi vil få en større andel av gammel skog. Dette resulterer i redusert tilvekst. Lageret av karbon i levende biomasse i skog har økt gjennom hele rapporteringsperioden (1990 – 2012), og fortsetter å øke i framskrivningene. Økningen i rapporteringsperioden skyldes blant annet en aktiv skogforvaltning de siste 60 – 70 årene. Den fremtidige økningen forutsetter at skogen som avvirkes re-etableres med samme treslag og produktivitet som skogen har i dag. Utslippsendringer for de øvrige arealkategoriene vil i større grad være betinget av arealendringer, hvor den totale størrelsen på opptak og utslipp påvirkes av størrelsen på arealet. Gitt en fortsettelse av trenden for perioden 2006 – 2010, vil den største endringen være i arealkategorien bebyggelse, som øker mest både i areal og prosent. Arealet med vann og myr og annen utmark vil være noenlunde stabilt, arealet skog og dyrket mark reduseres, mens arealet beite øker noe. Arealkategorien vann og myr bidrar til netto opptak. Dette skyldes karbonopptak i trær på tresatt myr (myrarealer med trær, men som ikke når skogdefinisjonen). Arealkategoriene dyrket mark, beite, bebyggelse og annen utmark har alle netto utslipp. Dyrket mark vil ha en reduksjon i netto utslipp gjennom de nærmeste 100 år, grunnet reduksjon i areal, mens utslippene fra beite kun vil ha små endringer.

Sammendrag

Formålet med denne rapporten er å gi en oversikt over skogressursene som grunnlag for vurdering av avvirkningsmulighetene, med hensyntaken til miljø og driftskostnader, i de neste 30 år. I rapporten gis en oversikt over dagens stående volum i hogstmoden skog (hogstklasse V), samt volum i skog som vil bli hogstmoden de kommende 30 år. Resultatene vises i form av tabeller og figurer der det er gjort ulike fratrekk for å ta høyde for reduksjoner grunnet miljøhensyn, driftskostnader og svinn. Brutto volum i dagens hogstklasse V utgjør vel 400 millioner kubikkmeter med bark. Vi har med bakgrunn i tilgjengelige data og et sett med forutsetninger estimert at miljøhensyn inkludert vern utgjør en reduksjon av tilgjengelig volum på 14 prosent. Kvantumet som vokser inn i hogstklasse V vil øke gjennom hele 30-årsperioden 2014-2043, fra litt under ni millioner kubikkmeter per år i første tiårsperiode til 13,7 millioner kubikkmeter per år i den tredje perioden (etter fradrag for miljøhensyn). Det er her tatt utgangspunkt i en framskriving av volumet til hogstmodenhetsalder. Dette volumet inkluderer imidlertid topp, bult, småtrær som ikke er nyttbare, og trær som ikke holder tømmerkvalitet (ofte kalt topp og avfall). Vi har med bakgrunn i data fra de permanente flatene i Landsskogtakseringen estimert reduksjonen ved omregning fra stående volum («skogskubikk») til volum som kan omsettes («tømmerkubikk») til 15 prosent. En vesentlig del av skogressursene er lokalisert i områder langt fra vei og/eller i bratt terreng, og gir ikke grunnlag for lønnsom skogsdrift gitt dagens driftskostnader, virkepriser og infrastruktur (skogsveier). Dette gjelder i størst grad den skogen som allerede er hogstmoden, mens den arealmessige fordelingen i forhold til driftsveilengde og terrengbratthet er gunstigere for skog som vokser inn i hogstklasse V de kommende tiår. Gitt at det relative forholdet mellom driftskostnader og virkepriser ikke endres vesentlig, vil vi få en en økt andel areal med positiv driftsnetto, noe som sannsynliggjør økt virketilgang i årene framover. Det er betydelige strukturelle forskjeller mellom den eksisterende hogstmodne skogen og skogen som blir hogstmoden de neste 30 år. En vesentlig forskjell er treslagsfordelingen, der gran utgjør 56 prosent av tilgangen av ny hogstmoden skog de neste 30 år, mens granandelen er kun 41 prosent i dagens hogstmodne skog. En økning av granandelen kan forventes i alle landets regioner og er en logisk følge av de historiske endringer i skogskjøtsel med økt planting av gran. En annen viktig observasjon er at over halvparten av tilgangen av hogstmoden skog de neste 30 år vil komme på det sentrale Østlandet, noe som vil styrke denne regionens rolle som det viktigste området for skogproduksjon. Etter fradrag for miljøhensyn og svinn, og ved kun å inkludere arealer med en estimert driftskostnad på maksimalt 250 kroner per kubikkmeter, synes det fullt forsvarlig ut fra ressursgrunnlaget å øke årlig hogstkvantum til om lag 15 millioner kubikkmeter («tømmerkubikk»). Dette under forutsetning av at tynningsuttaket framover holder seg minst på samme nivå som i dag. For å komme fram til et anslag på hva som er tilgjengelig for industriell bruk må det gjøres et ytterligere fradrag for virke som ikke kommer for salg (hjemmeforbruk, ved).

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Grantørkeprosjektet har fokusert på tørkeproblemer på gran i lavlandet på Østlandet. Toppskranting og avdøing har forekommet på enkelte lokaliteter i veksterlige granbestand i hkl 3-4. Gjentatte befaringer av slike skader gjennom de siste 20-25 år har tydet på at tørke er hovedårsaken, men at det er komplekse årsaksforhold. Det har vært et hovedmål i prosjektet å stille en diagnose på disse skadene. Videre har prosjektet fokusert på klimaendringene og risikoen for at tørkeskader på gran kan øke over tid. Endelig har prosjektet også tilrettelagt for en diskusjon mellom forskning, forvaltning og praktikere om skogbehandling og alternativer til konvensjonell skogbehandling med gran for å møte klimaendringene. Toppskrantingen som ble undersøkt i dette prosjektet hadde de samme symptomer som observert i mange tidligere befaringer, dvs. misfarging og avdøing av topper og gradvis forverring av skadene nedover i krona, etterfulgt av avdøing av hele trær. Resultatene bekrefter at tørkestress om sommeren har vært utløsende faktor for skadene, og at de undersøkte skadene i dette prosjektet ble utløst av moderat tørke i somrene 2004-06. Disse somrene hadde perioder i juni og juli med høy fordampning pga høye temperaturer og vedvarende vind, og lite nedbør. Dette førte til nedbørunderskudd og moderat tørkestress. Flere påfølgende år med moderat tørkestress har ført til kavitasjon i vannledningsbanene i stammen hos en del trær. Deler av yteveden har blitt satt ut av spill som vannledningsbaner. Utviklingen av høyde- og diametervekst, samt funn av tørkeringer og traumatiske harpikskanaler i disse årene understøtter at det har vært et tørkestress.....

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National Forest Inventories (NFIs) provide estimates of forest parameters for national and regional scales. Many key variables of interest, such as biomass and timber volume, cannot be measured directly in the field. Instead, models are used to predict those variables from measurements of other field variables. Therefore, the uncertainty or variability of NFI estimates results not only from selecting a sample of the population but also from uncertainties in the models used to predict the variables of interest. The aim of this study was to quantify the model-related variability of Norway spruce (Picea abies [L.] Karst) biomass stock and change estimates for the Norwegian NFI. The model-related variability of the estimates stems from uncertainty in parameter estimates of biomass models as well as residual variability and was quantified using a Monte Carlo simulation technique. Uncertainties in model parameter estimates, which are often not available for published biomass models, had considerable influence on the model-related variability of biomass stock and change estimates. The assumption that the residual variability is larger than documented for the models and the correlation of within-plot model residuals influenced the model-related variability of biomass stock change estimates much more than estimates of the biomass stock. The larger influence on the stock change resulted from the large influence of harvests on the stock change, although harvests were observed rarely on the NFI sample plots in the 5-year period that was considered. In addition, the temporal correlation between model residuals due to changes in the allometry had considerable influence on the model-related variability of the biomass stock change estimate. The allometry may, however, be assumed to be rather stable over a 5-year period. Because the effects of model-related variability of the biomass stock and change estimates were much smaller than those of the sampling-related variability, efforts to increase the precision of estimates should focus on reducing the sampling variability. If the model-related variability is to be decreased, the focus should be on the tree fractions of living branches as well as stump and roots.

Sammendrag

Harvest activity directly impacts timber supply, forest conditions, and carbon stock. Forecasts of the harvest activity have traditionally relied on the assumption that harvest is carried out according to forest management guidelines or to maximize forest value. However, these rules are, in practice, seldom applied systematically, which may result in large discrepancies between predicted and actual harvest in short-term forecasts. We present empirical harvest models that predict final felling and thinning based on forest attributes such as site index, stand age, volume, slope, and distance to road. The logistic regression models were developed and fit to Norwegian national forest inventory data and predict harvest with high discriminating power. The models were consistent with expected landowners behavior, that is, areas with high timber value and low harvest cost were more likely to be harvested. We illustrate how the harvest models can be used, in combination with a growth model, to develop a national business-as-usual scenario for forest carbon. The business-as-usual scenario shows a slight increase in national harvest levels and a decrease in carbon sequestration in living trees over the next decade.

Sammendrag

Med grunnlag i Landsskogtakseringens prøveflater beskriver denne rapport skogtilstanden på vernet areal samt vurder mulighetene for økt overvåking av vernet areal gjennom Landsskogtakseringen. I henhold til Landsskogtakseringens utvalgskartlegging er 2,3% av den produktive skogen vernet, mens andelen er 5,5% for den uproduktive skogen. Dette betyr at 3,1% (343 000 ha) av det totale skogarealet er vernet. Størsteparten av den vernete produktive skogen er i naturreservater (134 000 ha), mens nasjonalparkene utgjør en relativt liten del av det vernete produktive skogarealet (55 000 ha). Den mest vanlige skogtypen i vernområdene er bjørkedominert skog, det vil si arealer hvor over 70% av det stående volum er bjørk (120 000 ha). Et nesten like stort areal er furudominert (106 000 ha), mens grandominert skog utgjør et noe mindre areal (60 000 ha). Fordelingen av den vernete skogen på produktivitetsklasser viser at høyproduktiv og middels produktiv skog er underrepresentert, mens lavproduktiv og uproduktiv skog er overrepresentert. […]