Aksel Granhus
Head of Department/Head of Research
Authors
Aksel GranhusAbstract
No abstract has been registered
Authors
Inger Martinussen Mathias Amundsen Aksel Granhus Antje Gonera Marius Hauglin Anne Linn Hykkerud Laura Jaakola Mikko Kurttila Jari Miina Rainer Peltola Gesine Schmidt Josefine Skaret Baoru Yang Kjersti AabyAbstract
Almost 95% of the area in Norway is wilderness and 38% of the land area is covered by woods. These areas are abundant in valuable renewable resources, including wild berries. In our neighbouring countries, Sweden and Finland, wild berries are already a big industry. At the same time, on the market the Norwegian wild berries are almost non-existent and berries are left unexploited. Lingonberry (Vaccinium vitis-idaea) is one of the most abundant and economically important wild berries in the Nordic countries. Nevertheless, lingonberry has a large untapped potential due to its unique health effects and potential for increased value creation. It is estimated that 111,500 t of lingonberry are produced in the Norwegian woods. Norway is a long and diverse country with a range of climatic conditions. Adaptations to different conditions can give differences in both yield and quality of wild berries. Yields vary enormously from year to year and among different locations. A steady supply, predictable volumes and high quality are vital for successful commercialization of wild berries. To increase the utilization of berries, there is a need for increased knowledge regarding availability and quality variation of the berries. In addition, the Norwegian market suffers from high labour costs and cannot compete in product price. Innovative solutions and new knowledge on quality aspects can open possibilities for value creation. Toward achieving this goal, we have created a project called “WildBerries”, the main objective of which is to produce research-based knowledge that will create the basis for increased commercial utilization of Norwegian wild berries.
Abstract
Using periodic measurements from permanent plots in non-thinned and thinned Norway spruce (Picea abies (L.) H. Karst.) stands in Norway, individual-tree growth models were developed to predict annual diameter increment, height increment, and height to crown base increment. Based on long-term data across a range of thinning regimes and stand conditions, alternative approaches for modeling response to treatment were assessed. Dynamic thinning response functions in the form of multiplicative modifiers that predict no effect at the time of thinning, a rapid increase followed by an early maximum before the effect gradually declines to zero could not be fitted to initially derived baseline models without thinning related predictors. However, alternative approaches were used and found to perform well. Specifically, indicator variables representing varying time periods after thinning were statistically significant and behaved in a robust manner as well as consistent with general expectations. In addition, they improved overall prediction accuracy when incorporated as fixed effects into the baseline models for diameter and height to crown base increment. Further, more simply, including exponentially decreasing multiplicative thinning response functions improved prediction accuracy for height increment and height to crown base increment. Irrespective of studied attribute and modelling approach, improvement in performance of these extended models was relatively limited when compared to the corresponding baseline models and more pronounced in trees from thinned stands. We conclude that the largely varying and often multi-year measurement intervals of the periodic data used in this study likely prevented the development of more sophisticated thinning response functions. However, based on the evaluation of the final models’ overall performance such complex response functions may not to be necessary to reliably predict individual tree growth after thinning for certain conditions or species, which should be further considered in future analyses of similar nature.
Authors
Anne Catriona Mehlhoop Bram Van Moorter Christer Moe Rolandsen Dagmar Hagen Aksel Granhus Rune Eriksen Thor Harald Ringsby Erling Johan SolbergAbstract
Like large carnivores, hunters both kill and scare ungulates, and thus might indirectly affect plant performance through trophic cascades. In this study, we hypothesized that intensive hunting and enduring fear of humans have caused moose and other forest ungulates to partly avoid areas near human infrastructure (perceived hunting risk), with positive cascading effects on recruitment of trees. Using data from the Norwegian forest inventory, we found decreasing browsing pressure and increasing tree recruitment in areas close to roads and houses, where ungulates are more likely to encounter humans. However, although browsing and recruitment were negatively related, reduced browsing was only responsible for a small proportion of the higher tree recruitment near human infrastructure. We suggest that the apparently weak cascading effect occurs because the recorded browsing pressure only partly reflects the long-term browsing intensity close to humans. Accordingly, tree recruitment was also related to the density of small trees 5–10 years earlier, which was higher close to human infrastructure. Hence, if small tree density is a product of the browsing pressure in the past, the cascading effect is probably stronger than our estimates suggest. Reduced browsing near roads and houses is most in line with risk avoidance driven by fear of humans (behaviorally mediated), and not because of excessive hunting and local reduction in ungulate density (density mediated).
Authors
Ricardo Ruiz-Peinado Hans Pretzsch Magnus Löf Michael Heym Kamil Bielak Jorge Aldea Ignacio Barbeito Gediminas Brazaitis Lars Drössler Kšištof Godvod Aksel Granhus Stig-Olof Holm Aris Jansons Ekaterina Makrickienė Marek Metslaid Sandra Metslaid Arne Nothdurft Ditlev Otto Juel Reventlow Roman Sitko Gintarė Stankevičienė Miren del RíoAbstract
Mixed-species stands have been found to be more productive than would be expected from the performance of their component species in monocultures due to facilitation and complementarity between species, although these interactions depend on the combination of species present. Our study focuses on monospecific and mixed-species stands of Scots pine and Norway spruce using 20 triplets established in nine countries along a climatic gradient across Europe. Differences in mean tree and stand characteristics, productivity and stand structure were assessed. Basal area increment in mixed stands was 8% higher than expected while volume increment was only 2% greater. Scots pine trees growing in mixed-species stands showed 11% larger quadratic mean diameter, 7% larger dominant diameter, 17% higher basal area and 25% higher stand volume than trees growing in monospecific stands. Norway spruce showed only a non-significant tendency to lower mean values of diameters, heights, basal area, as well standing volume in mixtures than monocultures. Stand structure indices differed between mixed stands and monocultures of Scots pine showing a greater stratification in mixed-species stands. Furthermore, the studied morphological traits showed little variability for trees growing in monospecific stands, except for diameter at breast height, crown length and crown length ratio. For trees growing in mixed stands, all the morphological traits of the trees were identified as different. Some of these morphological traits were associated with relative productivity. Nevertheless, relative productivity in mixed-species stands was not related to site conditions.
Abstract
Field-based monitoring of deer food availability and browsing on recruiting forest trees is a necessary but labour-intensive task. We explored how such estimates from a low-resolution multipurpose national forest inventory (NFI) (plot density 0.3 km−2) corresponded with estimates from local inventories that specifically and in greater detail monitor the availability of deer food and browsing intensity (LFI) (plot density 2–3 km−2). We used NFI and LFI data from 16 moose Alces alces ranges (mean area 276 ± SE 69 km2) in southern Norway. Only the height segment 30–130 cm of browsable trees could be obtained from the NFI data, while moose can browse trees from 30 to 300 cm in height. According to the LFI, the browse species did not have similar proportions of their browsable stems below 130 cm. Using only the stems from heights of 30–130 cm overestimated the availability of RAS (rowan, aspen and sallow) relative to birch (silver birch and downy birch) and Scots pine. The browsable biomass per stem of each species also varied between ranges, which introduces uncertainty to the food availability estimates that are based on stems only. Nevertheless, the NFI density of stems at 30–130 cm heights can be a useful index for species-specific comparisons of browse availability across ranges, because the variations between ranges in stem densities outweighed the biomass variations per stem. The NFI and LFI estimates of the species-specific densities of stems at 30–130 cm heights were significantly related and close to isometric (1:1), especially for RAS and pine. We did not find strong relationships between NFI and LFI in the browsing intensity (i.e. proportion of shoots that were browsed during the winter). The explained variation was only 11% (R2) for RAS (p = 0.281) and 32% for pine (p = 0.028). This was likely due to the small sample sizes of browsed trees in the NFI and methodological differences between the NFI and LFI in how browsing intensity is estimated. Conclusions Using data from national forest inventories can be an efficient but low-resolution way to monitor browse availability for deer, provided that the monitoring includes the full range of tree heights reachable for the deer (e.g., 30–300 cm for moose). It is also a prerequisite that the number of NFI plots is sufficient to cover the spatial variability of the area. Regarding browsing intensities, adjustments in both the NFI and LFI approaches are needed to make the two monitoring schemes more comparable.
Authors
Jorge Aldea Ricardo Ruiz-Peinado Miren del Río Hans Pretzsch Michael Heym Gediminas Brazaitis Aris Jansons Marek Metslaid Ignacio Barbeito Kamil Bielak Aksel Granhus Stig-Olof Holm Arne Nothdurft Roman Sitko Magnus LöfAbstract
Mixed forests are suggested as a strategic adaptation of forest management to climate change. Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) are tree species of high economic and ecological value for European forestry. Both species coexist naturally in a large part of their distributions but there is a lack of knowledge on the ecological functioning of mixtures of these species and how to manage such stands. This paper analyses these species' intra-and inter-specific competition, including size-symmetric vs. size-asymmetric competition, and explore the effect of weather conditions on tree growth and competition. We studied basal area growth at tree level for Scots pine and Norway spruce in mixed versus pure stands in 22 triplets of fully-stocked plots along a broad range of ecological conditions across Europe. Stand inventory and increment cores provided insights into how species mixing modifies tree growth compared with neighbouring pure stands. Five different competition indices, weather variables and their interactions were included and checked in basal area growth models using a linear mixed model approach. Interspecific size-asymmetric competition strongly influenced growth for both tree species, and was modulated by weather conditions. However, species height stratification in mixed stands resulted in a greater tree basal area growth of Scots pine (10.5 cm 2 year − 1) than in pure stands (9.3 cm 2 year − 1), as this species occupies the upper canopy layer. Scots pine growth depended on temperature and drought, whereas Norway spruce growth was influenced only by drought. Interspecific site-asymmetric competition increased in cold winters for Scots pine, and decreased after a drought year for Nor-way spruce. Although mixtures of these species may reduce tree size for Norway spruce, our results suggest that this could be offset by faster growth in Scots pine. How inter-specific competition and weather conditions alter tree growth may have strong implications for the management of Scots pine-Norway spruce mixtures along the rotation period into the ongoing climate change scenario.
Abstract
Spondylosis deformans is a spinal disease common to several dog breeds, and several treatments including veterinary chiropractic may be used to treat affected dogs. Little is known, however, about the efficacy of chiropractic treatment as precautionary measure, aiming to reduce the probability of spondylosis development. We performed a randomized study where one half of the Boxer puppies from 17 litters were given veterinary chiropractic treatment at monthly intervals from eight weeks of age until they were one year old, while the other half were given no treatment (treated: n = 44, controls: n = 43). At an age of one year, spondylosis occurrence was recorded based on a scoring of X-ray images of the spine. The frequency of occurrence was significantly lower (p = 0.0478) in the treated dogs (25.0%) than in the controls (46.5%). We also tested if spondylosis occurrence in the treated dogs correlated with the average number of spinal joints with decreased mobility found per chiropractic treatment. No such effect was found, however. In summary, our results suggest that veterinary chiropractic treatment may be successfully used to reduce the probability of early development of spondylosis in young Boxers.
Abstract
Past: In the early twentieth century, forestry was one of the most important sectors in Norway and an agitated discussion about the perceived decline of forest resources due to over-exploitation was ongoing. To base the discussion on facts, the young state of Norway established Landsskogtakseringen – the world’s first National Forest Inventory (NFI). Field work started in 1919 and was carried out by county. Trees were recorded on 10 m wide strips with 1–5 km interspaces. Site quality and land cover categories were recorded along each strip. Results for the first county were published in 1920, and by 1930 most forests below the coniferous tree line were inventoried. The 2nd to 5th inventories followed in the years 1937–1986. As of 1954, temporary sample plot clusters on a 3 km × 3 km grid were used as sampling units. Present: The current NFI grid was implemented in the 6th NFI from 1986 to 1993, when permanent plots on a 3 km × 3 km grid were established below the coniferous tree line. As of the 7th inventory in 1994, the NFI is continuous, and 1/5 of the plots are measured annually. All trees with a diameter ≥ 5 cm are recorded on circular, 250 m2 plots. The NFI grid was expanded in 2005 to cover alpine regions with 3 km × 9 km and 9 km × 9 km grids. In 2012, the NFI grid within forest reserves was doubled along the cardinal directions. Clustered temporary plots are used periodically to facilitate county-level estimates. As of today, more than 120 variables are recorded in the NFI including bilberry cover, drainage status, deadwood, and forest health. Landuse changes are monitored and trees outside forests are recorded. Future: Considerable research efforts towards the integration of remote sensing technologies enable the publication of the Norwegian Forest Resource Map since 2015, which is also used for small area estimation at the municipality level. On the analysis side, capacity and software for long term growth and yield prognosis are being developed. Furthermore, we foresee the inclusion of further variables for monitoring ecosystem services, and an increasing demand for mapped information. The relatively simple NFI design has proven to be a robust choice for satisfying steadily increasing information needs and concurrently providing consistent time series.
Abstract
In this study, we aim at developing ways to directly translate raw drone data into actionable insights, thus enabling us to make management decisions directly from drone data. Drone photogrammetric data and data analytics were used to model stand-level immediate tending need and cost in regeneration forests. Field reference data were used to train and validate a logistic model for the binary classification of immediate tending need and a multiple linear regression model to predict the cost to perform the tending operation. The performance of the models derived from drone data was compared to models utilizing the following alternative data sources: airborne laser scanning data (ALS), prior information from forest management plans (Prior) and the combination of drone +Prior and ALS +Prior. The use of drone data and prior information outperformed the remaining alternatives in terms of classification of tending needs, whereas drone data alone resulted in the most accurate cost models. Our results are encouraging for further use of drones in the operational management of regeneration forests and show that drone data and data analytics are useful for deriving actionable insights. Key words: UAV, DAP, forest inventory, photogrammetry, precommercial thinning, airborne laser scanning.
Abstract
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.
Abstract
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Abstract
Short-day (SD) treatment is used by forest nurseries to induce growth cessation in Picea abies seedlings. SD treatment may however increase the risk of reflushing in autumn and earlier bud break the following spring. When the start of the SD treatment is early in order to control seedling height, the duration of the SD treatment should be longer in order to prevent reflushing in autumn. However, due to the amount of manual work involved in the short-day treatment, increasing the number of days is undesirable from a practical point of view. Splitting the SD treatment could be a way to achieve both early height control and at the same time avoid autumn bud break with less workload. We tested how different starting dates and durations of SD treatment influenced on morphological and phenological traits. Regardless of timing and duration of the SD treatment, height growth was reduced compared to the untreated controls. Seedlings given split SD (7+7 days interrupted with two weeks in long days) had less height growth than all other treatments. Root collar diameter growth was significantly less in control seedlings than in seedlings exposed to early (7 or 14 days) or split (7+7 days) SD treatment. There were also differences in the frequency of reflushing and bud break timing among the SD treated seedlings, dependent on duration and starting date. If the SD treatment started early, a continuous 14-day SD treatment was not sufficient to avoid high frequencies of reflushing. However, by splitting the SD treatment into two periods of 7+7 days these negative effects were largely avoided, although spring bud break occurred earlier than in the controls.
Abstract
The objective of this study was to assess the use of unmanned aerial vehicle (UAV) data for modelling tree density and canopy height in young boreal forests stands. The use of UAV data for such tasks can be beneficial thanks to the high resolution and reduction of the time spent in the field. This study included 29 forest stands, within which 580 clustered plots were measured in the field. An area-based approach was adopted to which random forest models were fitted using the plot data and the corresponding UAV data and then applied and validated at plot and stand level. The results were compared to those of models based on airborne laser scanning (ALS) data and those from a traditional field-assessment. The models based on UAV data showed the smallest stand-level RMSE values for mean height (0.56 m) and tree density (1175 trees ha−1 ). The RMSE of the tree density using UAV data was 50% smaller than what was obtained using ALS data (2355 trees ha−1 ). Overall, this study highlighted that the use of UAVs for the inventory of forest stands under regeneration can be beneficial both because of the high accuracy of the derived data analytics and the time saving compared to traditional field assessments.
Abstract
Root rot in Norway spruce (Picea abies (L.) Karst.) causes substantial economic losses to the forestry sector. In this study, we developed a probability model for decay at breast height utilizing 18,141 increment cores sampled on temporary plots of the Norwegian National Forest Inventory. The final model showed a good fit to the data and retained significant relationships between decay and a suite of tree, stand and site variables, including diameter at breast height, stand age, altitude, growing season temperature sum (threshold 5°C), and vegetation type. By comparing model predictions with recorded decay at stump height in an independent data set, we estimated a proportionality function to adjust for the inherent underestimation of total rot that will be obtained by applying a probability model derived from increment cores sampled at breast height. We conclude that the developed model is appropriate for national and regional scenario analyses in Norway, and could also be useful as a tool for operational forestry planning. This would however require further testing on independent data, to assess how well the new model predicts decay at local scales.
Authors
Aksel GranhusAbstract
No abstract has been registered
Abstract
The ericaceous shrub bilberry (Vaccinium myrtillus L.) is a keystone species of the Eurasian boreal forest. The most optimal light condition for this plant is partial shading. Shade from the forest canopy depends on the stand density, a forest attribute that can be manipulated by forest managers. Most previous studies of the relationship between bilberry abundance and forest density have not explored the potentially modifying impacts of factors like stand age, tree species composition, and the solar irradiation at the site, as determined by location and topography. Using data from the Norwegian National Forest Inventory, we developed a generalized linear model applicable to estimate local bilberry cover across a wide range of environmental conditions in Norway. The explanatory terms in the final model were stand density (basal area per ha), solar irradiation, stand age, percentages of deciduous, pine, and spruce trees, summer (June-August) mean temperature and precipitation sum, mean temperature in January, site index, and soil category, in addition to the two-way interactions between stand density and the following: solar irradiation, stand age, percentage of deciduous trees, and percentage of Norway spruce (Picea abies). The final model explained ca. 21% of the total variation in bilberry cover. We conclude that a stand density of c. 30 m2 ha−1 in general will create favourable conditions for bilberry. If the forest is younger than 80 years old, or dominated by Norway spruce or deciduous trees, the optimal stand density is reduced to around 20 m2 ha−1. In a forest dominated by Scots pine (Pinus sylvestris), basal areas up to 40 m2 ha−1 would be beneficial to bilberry abundance. Our results demonstrate the importance of considering interactions between stand density and other stand and site characteristics.
Abstract
In the Nordic-Baltic region, there has been a growing concern about an increasing occurrence of multiple tops in young stands of Norway spruce. There is however a lack of documentation on the amount of such damages, and the causal agents involved. In two separate studies in SE Norway, we assessed the frequency of multiple tops in young sapling-sized stands, and studied the relationship between the occurrence of multiple tops and lammas growth the previous growing season on the sample trees. Study 1 included 44 planted and 10 naturally regenerated stands, while Study 2 included 68 planted stands with information on seed source. Among sample trees with multiple tops, 57% (Study 1) and 32% (Study 2) had signs of lammas growth the previous autumn, either in the form of an extended leading shoot or swollen bud. Site index as well as sample tree height were positively correlated to the occurrence of both lammas growth and multiple tops in both studies. In Study 1 we show that the probability of lammas growth was significantly higher in planted than in naturally regenerated stands. In Study 2 we show that it was higher in stands planted with seedlings grown from stand-origin seeds compared with improved seed material. Furthermore, the results of both studies show that lammas growth occurs most frequently among the dominant trees in the stand.
Abstract
Natural regeneration of Norway spruce (Picea abies (L.) Karst.) is a relatively common practice in Norway on medium to low site indices. However, seedling establishment is often hampered by rapid regrowth of competing vegetation in scarified patches. The aim of our study was to examine the effect of coordinating scarification towards an expected seed-fall, by studying germination and seedling establishment in scarified patches of different age (fresh, one- and two-year-old). The experiment was conducted in two stands in southeast Norway that were clear-cut in 2007. Scarification was applied to subplots in autumn 2008–2010. To simulate seed-fall, seeds were sown in fresh scarification patches in spring 2009–2011, in one-year-old patches in 2010 and 2011, and in twoyear- old patches in 2011. Both germination and seedling survival were negatively affected by the age of the scarified patches. Germination was higher, and mortality lower, at the small fern woodland site, compared with the bilberry woodland site. Sowing in fresh patches also resulted in increased height and root collar diameter of the seedlings compared with sowing in older patches. It is likely that the competing vegetation both on the site and in the scarification patches affected the growth of the seedlings. In conclusion, the age of the scarified patches affected both germination and mortality, as well as early growth of the seedlings.
Abstract
Removal of logging residues causes significant nutrient losses from the harvesting site. Furthermore,collection of residues into piles could lead to small-scale differences in establishment conditions for seedlings. We studied the effects of stem-only (SOH) and aboveground whole-tree harvesting (WTH) on Norway spruce (Picea abies) seedling growth and pine weevil (Hylobius abietis) damage at two sites (SE and W Norway). We also compared two planting environments within the WTH plots (WTH-0: areas with no residues, WTH-1: areas where residue piles had been placed and removed before planting). In practice, one-third of the residues were left on site after WTH. After three growing seasons there were no differences for height or diameter increment between SOH and WTH (WTH-1 and WTH-0 combined) treatments. However, relative diameter increment was largest for WTH-1 seedlings and lowest for WTH-0 seedlings. Few seedlings sustained pine weevil attacks at the W Norway site, with no differences among treatments. At the SE Norway site, the percent of seedlings damaged by pine weevils and average debarked area were significantly higher after WTH (82% and 3.3 cm2) compared to SOH (62% and 1.7 cm2). We conclude that WTH may lead to spatial differences in establishment conditions.
Abstract
The goal of this study was to assess the long-term effects of partial harvesting and supplementary soil scarification on the frequency of root and butt rot in managed uneven-sized Norway spruce stands. Frequency of rot and the population structure of the rot fungi were assessed on 1353 stumps after clear-cutting 21 years after a selection harvesting experiment. The initial experiment was comprised of three harvest strength (low, intermediate and high) of single-tree selection, removing approximately 25, 45 and 65% of the stand basal area. Uncut control plots were established at the same time. Supplementary soil scarification was applied in subplots within the single-tree selection plots, using a medium-sized excavator. After clear-cutting the stumps were analyzed with respect to rot caused by Heterobasidion parviporum, Armillaria spp., Stereum sanguinolentum as well as other rot fungi. Rot caused by Armillaria spp. was most common (8.6% of the stumps), while infection by H. parviporum (2.9%) or S. sanguinolentum (3.0%) was less frequent. The group “other rot” (5.4%) comprised 21 identified taxa, each occurring in 1–15 stumps. Significantly lower rot frequencies were found for the uncut control (16.3%) and intermediate harvest strength (15.7%), compared with low harvest strength (23.6%). A rot frequency of 21.0% was found in the high harvest strength. In two of three harvest strengths, the rot frequency was higher than for the uncut control. As the observed rot frequencies did not increase consistently with increasing harvest strength, the results do not completely support the initial expectations of increased rot after single-tree selection compared with the uncut control. However, since the probability of rot in individual stumps on plots treated with single-tree selection was significantly affected by the distance to the nearest strip road (H. parviporum) as well as dependent on the size of and distance to the nearest stump of trees cut during the experimental harvest (H. parviporum, S. sanguinolentum and total rot), it is evident that the single-tree selection harvesting was partially responsible for some of the observed rot. One of the selection criteria in the initial harvest was a sanitary removal of trees of poor vitality. Varying degrees of sanitation felling may therefore have offset the effects of new infections in wounds or spread of rot fungi through adjacent stumps. Supplementary soil scarification in small gaps of the residual stand had no significant effect on the frequency of rot, suggesting that such treatment may be used to facilitate regeneration in uneven-sized spruce stands on similar sites.
Abstract
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Authors
Signe Nybø Bård Pedersen Olav Skarpaas Iulie Aslaksen Jarle W. Bjerke Gregoire Certain Hanne Edvardsen Erik Framstad Per Arild Garnåsjordet Aksel Granhus Hege Gundersen Snorre Henriksen Knut Anders Hovstad Anders Jelmert Margaret McBride Ann Norderhaug Geir Ottersen Eivind Oug Hans-Christian Pedersen Ann Kristin Schartau Ken Olaf Storaunet Gro Ingleid van der MeerenAbstract
No abstract has been registered
Authors
Signe Nybø Bård Pedersen Olav Skarpaas Iulie Aslaksen Jarle W. Bjerke Gregoire Certain Hanne Edvardsen Erik Framstad Per Arild Garnåsjordet Aksel Granhus Hege Gundersen Snorre Henriksen Knut Anders Hovstad Anders Jelmert Margaret McBride Ann Norderhaug Geir Ottersen Eivind Oug Hans-Christian Pedersen Ann Kristin Schartau Ken Olaf Storaunet Gro Ingleid van der MeerenAbstract
No abstract has been registered
Abstract
Norway spruce (Picea abies (L.) Karst.) understory seedlings, growing in partially harvested plots with different canopy cover in a boreal spruce stand, were spot fertilized (Hydro 15-4-12) 9 years after planting. The principal aimwasto test the hypothesis that nitrogen (N)availability influences growthof understory seedlings at intermediate but not at lowlevels of irradiance. In addition, we tested the combined influences of N and light availability on selected morphological and phenological traits, covering a 2-year period after treatment. Diffuse radiation (DIFR) at the seedling level was estimated from hemispherical photographs and ranged from 19 to 46 per cent of DIFR in openconditions. Fertilizer applicationwasassociatedwithamarkedincreasein foliarNconcentration.Thefertilized seedlings grew better in height and root collar diameter compared with unfertilized controls. While the absolute growth in both diameterand height increased with increasing DIFR, seedlings also responded to improved nutrient availability across the rangeof light conditions studied. Fertilizer treatment did not affect thenumberof nodal buds, but we observed a higher apical dominance ratio and advanced bud burst in fertilized seedlings. In conclusion, nutrient availability influenced growth and bud phenology of understory Norway spruce seedlings at least down to 20 per cent DIFR.
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No abstract has been registered
Authors
Aksel GranhusAbstract
No abstract has been registered
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No abstract has been registered
Authors
Gunnhild Søgaard Aksel Granhus Belachew Gizachew Zeleke Nicholas Clarke Kjell Andreassen Rune EriksenAbstract
Miljødirektoratet utarbeidet i 2014 et kunnskapsgrunnlag for hvordan vi kan omstille Norge til et lavutslippssamfunn (Miljødirektoratet 2014). I rapporten ble en rekke tiltak i skog beskrevet. Denne rapporten er en del av neste fase av dette arbeidet, som er å utdype analysen av mulige tiltak og virkemidler. Her beskriver vi, på oppdrag fra Miljødirektoratet, et utvalg klimatiltak i skog. Det er på ingen måte noen uttømmende oversikt over klimatiltak, men dekker et utvalg som det var ønske om å belyse nærmere. Disse er belyst nærmere med hovedvekt på karbonopptak og –lagring. Betydning for andre økosystemtjenester, som for eksempel biodiversitet og friluftsliv, er ikke belyst. Hovedkonklusjonene fra dette arbeidet kan kort oppsummeres slik: Fra 1990 og frem til 2012 har et bruttoareal på 1,4 mill. daa blitt avskoget (NIR 2014). Basert på data fra Landsskogtakseringen ser vi at den viktigste årsaken er nedbygging av skogareal til ulike formål (73 % av arealet), etterfulgt av omdisponering til beite (16 %). Om lag 29 % av skogen som avvirkes, hogges før hogstmodenhetsalder. Av dette arealet utgjør hogstklasse IV 25 %, mens hogstklasse III eller yngre utgjør 4 %. Skog definert som ”yngre skog” etter forslag til revidert PEFC skogstandard utgjør 9 %. Generelt benyttes relativt skånsomme metoder for markberedning i Norge i dag, og disse er vurdert til sannsynligvis å ha liten eller ingen effekt på karbonmengder i jorda over tid og over det totale areal. Tettere planting gir høyere volumproduksjon tidlig i bestandets liv. I følge resultatkontrollen i 2013 hadde 29 % av det totale foryngelsesarealet et plantetall under anbefalt nivå i bærekraftforskriften. Framskrivningene av skogbestokningen viser at en fortsettelse av dagens praksis på årlig foryngelsesareal fra 2015 og frem til 2100 akkumulert gir 83,5 millioner tonn CO2 lavere opptak enn om arealet hadde vært plantet med anbefalt tetthet. Høyere plantetetthet gir også økt mulighet for å ta ut virke gjennom tynning. Vi mener det er potensial for økt tynningsaktivitet, uten at dette vil redusere produksjon (opptak) på lenger sikt. Tynning kan øke potensialet for mer bruk av GROT (heltretynning). Ved tynning og gjødsling kan andelen sagtømmer i det hogstmodne bestandet øke, og samtidig kan tynning være ønskelig for å lage stabile bestand som kan overholdes utover normal hogstmodenhetsalder. Uttak av hogstrester (GROT) gir råstoff til bioenergi, som kan brukes til å erstatte fossile brensler. Forutsatt høstet på en bærekraftig måte, kan uttaket av GROT sannsynligvis økes uten redusert fremtidig produksjon (opptak). En lavskjerm med bjørk over granforyngelse vil, dersom den skjøttes riktig, gi en høyere total volumproduksjon på arealet over ett omløp sammenlignet med et renbestand med gran.
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Aksel GranhusAbstract
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Heleen de Wit Aksel Granhus Markus Lindholm Martin J. Kainz Yan Lin Hans Fredrik Veiteberg Braaten Joanna BlaszczakAbstract
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Ragnar Johnson Mika Mustonen Tomas Lundmark Annika Nordin Yuri Gerasimov Aksel Granhus Eugene Hendrick Jari Hyninen Vivian Kvist Johannesen Adam Kaliszewski Virginijus Miksis Thomas Nord-Larsen Heino Polley Liana Sadauskiene Pat Snowdon Birger Solberg Erik Sollander Arnor Snorrason Mati Valgepea Sheila Ward Toms ZalitisAbstract
Forests will play a crucial role in the transformation from an economy based on fossil fuels to one relying on renewable resources. Hence, besides being a source of raw material for the forest industry, in the future, forests are expected to increasingly contribute to the production of energy as well as providing a wide range of environmental and social services. Thus, the objective of the present study is to assess the short-term and long-term potential for increasing sustainable wood supply in the EFINORD countries. Present practices and prospects for intensive forest management have been assessed using information from a questionnaire complemented by compilation and evaluating of national forest inventory (NFI) data and other forest sector relevant information. The study indicates a striking variation in the intensity of utilisation of the wood resources within the EFINORD region. For the region as a whole, there seems to be a substantial unused (biophysical) potential. However, recent NFI data from some countries indicate that annual felling rates can be underestimated. If felling rates are higher than currently recognised then, given the increased demand for wood-based energy, there appears to be a need to discuss strategies for large-scale implementation of more intensive forestry practices to ensure that the availability of wood resources in the future can meet an increasing demand in the EFINORD countries.
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In this report, the oral and poster contributions of the scientific conference “Forest Management and Silviculture in the North – Balancing Future Needs” have been compiled. The conference was arranged 6-8 September 2011 in Stjørdal, Norway, gathering more than 50 delegates from seven countries. The conference was hosted by the Norwegian Forest and Landscape Institute and was initiated jointly by IUFRO WP 1.01.01 Boreal forest silviculture and management and the SNS network group Sustainable forest management in northern Fennoscandia (NORFOR).
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Four Norway spruce stands treated with single tree selection were studied 11 years after the cuttings. In each of the stands we performed four strengths of cuttings in 0.2 ha plots, with removals ranging from zero to 70 % of the basal area. We investigated accumulated and annual growth, changes in stand structure, tree age and tree damage. 10-20 % of the living trees were still damaged 11 years after the cutting. The diameter distribution displayed a reverse J-curve in all plots both before and after the cuttings. Eleven years later, the curve is only slightly changed. Annual ring widths from 300 increment cores were analysed. Most trees started to increase the growth two or three years after the cutting. This improved growth accelerated the following six or seven years with 20-80 % increase. Both small and large trees reacted, including severely suppressed trees. The initial crown volume and crown vitality after cutting is essential for the increased growth since several years are necessary to build up a larger and better crown. A reduced volume per hectare provided an increased growth for each of the remaining trees and indicates less competition for nutrients and light after cutting. The observed growth during the 11-year post-harvest period was about 10 % less than the estimated yield capacity for even-aged stands.
Authors
Gunnhild Søgaard Inger Sundheim Fløistad Aksel Granhus Kjersti Holt Hanssen Harald Kvaalen Tore Skrøppa Arne SteffenremAbstract
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Le gel printanier peut etre dommageable pour les semis de Picea abies (L.) Karst. nouvellement plantes si leur rythme de croissance n'est pas suffisamment adapte aux conditions climatiques de la station forestiere. Les objectifs de cette etude consistaient a determiner de quelle facon le debourrement et la resistance au gel printanier sont influences par un traitement de jours courts (JC) appliques a differents moments et avec differents regimes de temperature durant la periode de formation des bourgeons. A la suite d'un entreposage hivernal, la resistance au gel a ete evaluee apres une, trois et cinq semaines dans des conditions de forcage. Le traitement JC a avance le debourrement comparativement aux semis temoins. Par comparaison, le moment du traitement et les differentes temperatures ont eu peu d'effet sur le debourrement. Le traitement JC a augmente la resistance au gel des aiguilles d'un an pendant la periode de desendurcissement. Applique tot, le traitement JC a augmente la resistance au gel des aiguilles d'un an et le diametre au collet comparativement a une application plus tardive. Il est important que la periode de noirceur atteigne une duree critique lorsque le traitement JC prend fin pour eviter une deuxieme eclosion des bourgeons. Des temperatures basses a la suite du traitement JC ont augmente la resistance au gel des aiguilles et diminue celle de la tige. Les effets contraires de la temperature sur differents tissus vegetaux demontrent l'importance d'examiner differents tissus apres des essais de gel-degel. Spring frost may result in detrimental damage in newly planted Picea abies (L.) Karst. seedlings if their growth rhythm is not sufficiently adapted to the climatic conditions on the forest site. The aims of this study were to evaluate how bud break and spring frost hardiness were influenced by short-day (SD) treatments with different timing and different temperature regimes during bud formation. Following winter storage, frost hardiness was tested after 1, 3 and 5 weeks in forcing conditions. The SD treatment advanced bud break compared with the control seedlings. In comparison, the effects of timing and the different temperatures on bud break were small. The SD treatment improved frost hardiness in first-year needles during dehardening. The early SD treatment resulted in improved frost hardiness in first-year needles and greater root collar diameter compared with later SD treatment. To avoid a second bud flush, it is important that a critical night length is attained when the SD treatment terminates. Low temperatures following the SD treatment resulted in increased hardiness of the needles and decreased hardiness of the stems. The contrasting effect of temperature in different plant tissues demonstrates the importance of examining different tissues following freezing tests.
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In trees adapted to cold climates, conditions during autumn and winter may influence the subsequent timing of bud burst and hence tree survival during early spring frosts. We tested the effects of two temperatures during, dormancy induction Mid mild spells (MS) during chilling, on the timing of bud burst in three Picea abies (L.) Karst. provenances (58-66 degrees N). One-year-old seedlings were induced to become dormant at temperatures of 12 or 21 degrees C applied during 9 weeks of short days (12-h photoperiod). The seedlings were then moved to cold storage and given either continuous chilling at 0.7 degrees C (control), or chilling interrupted by one 14-day MS it either 8 or 12 degrees C. Interruptions with MS were staggered throughout the 175-day chilling period, resulting in 10 MS differing in date of onset. Subsets of seedlings were moved to forcing conditions (12-h photoperiod, 12 degrees C) throughout the chilling period, to assess dormancy status different timings of the MS treatment. Finally, after 175 days of chilling, timing of bud burst was assessed in a 24-h photoperiod at 12 degrees C (control and MS-treated seedlings). The MS treatment did not significantly affect days to bud burst when given early (after 7-35 chilling days). When MS was given after 49 chilling days or later, the seedlings burst bud earlier than the controls, and the difference increased with increasing length of the chilling period given before the MS. The 12 degrees C MS treatment was more effective than the 8 degrees C MS treatment, and the difference remained constant after the seedlings had received 66 or more chilling days before the MS treatment was applied. In all provenances, a constant temperature of 21 degrees C during dormancy induction resulted in more dormant seedlings (delayed bud burst) than a constant temperature of 12 degrees C, but this did not delay the response to the MS treatment.
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Manipulation of the canopy cover and site preparation are the most important silvicultural measures to enhance the conditions for natural regeneration of Norway spruce (Picea abies (L.) Karst.). During the early regeneration phase however, seedling mortality may be high, so it is important to study how different combinations of stand-level treatments and site preparation methods affect seedling establishment. We studied emergence, 1st winter and 2nd summer mortality for naturally regenerated spruce seedlings in a field experiment that combined four harvest treatments (shelterwoods of high (SH), medium (SM) and low (SL) residual basal area, and a 50 x 50 m clear-cut (CC)) and two site preparation methods (patch scarification and inverting). The CC had significantly fewer seedlings the 1st fall than the SL and SH (p = 0.0377), and in all harvest treatments, fewer seedlings emerged in inverted than in patch scarified spots (p = 0.0351). Mortality was also lower with patch scarification than inverting (1st winter: p = 0.0565, 2nd summer: p = 0.0377), but was not affected by harvest treatment (1st winter: p = 0.9211, 2nd summer: p = 0.1896). On average, mortality from 1st to 2nd fall reached 38% and 27% after inverting and patch scarification, respectively. First winter mortality accounted for approximately two thirds of the accumulated mortality, regardless of the harvest treatment and site preparation method.
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Michelle de Chantal Kjersti Holt Hanssen Aksel Granhus Urban Bergsten Mikaell Ottosson-Löfvenius Harald GripAbstract
We studied first winter frost-heaving damage to one-year-old Picea abies (L.) Karst. seedlings planted in gaps made by group fellings (large circular gaps, ca. 500 m(2)) and single-tree selection cuttings (small irregularly shaped gaps, ca. 175 m 2), as well as in uncut forest. One-month-old seedlings were planted on manually exposed LF, Ae, and B horizons that emulated various intensities and depths of scarification. The three experimental sites were located in multistoried Pinus sylvestris L. or P. abies forests on sandy loam or silt loam in southeastern Norway. Altogether, 5% of seedlings sustained frost heaving damage on the LF horizon, compared with 20% on the Ae horizon and 45% on the B horizon. On average, 31% of the seedlings in large gaps incurred frost-heaving damage compared with 20% in small gaps and 19% in uncut forest. Exposed roots and poorly anchored or uplifted seedlings were recurring classes of damage, especially on the B horizon and in large gaps. The above- versus below-ground biomass ratio of seedlings was higher on the B than on the Ae horizon in uncut forest and large gaps, inferring broken roots. Therefore, to reduce the risk of frost-heaving damage, shallow soil preparation and smaller gap sizes should be used.
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According to previous studies, short day (SD) treatment may increase frost hardiness in Picea abies (L.) Karst. seedlings during shoot elongation the next year. The purpose of this study was to examine how timing of the SD treatment affects spring frost hardiness. The following four treatments were applied in the first growth period: natural photoperiod (Nat), or SD treatment (8/16 h, day/night) either from 14-28 July (SD1), 28 July-11 August (SD2), or 11 20 August (SD3). After 125 days in the cold store (October-January), the seedlings were transferred to forcing conditions (20-25oC, 24 h photoperiod) followed by freezing tests at 3, -5, -7 and 9oC when most seedlings had reached bud break stage 7 (Krutzsch index). Seedling height measurements and analyses of carbohydrate status, nitrogen concentration and dry weight of needles after cold storage were done to examine the treatments` impact on seedling quality. SD treatment reduced visual freezing injury to current- and first-year shoots. Mortality occurred at –7 and –9oC and was significantly higher in treatments Nat and SD1 (43% in both) than in the SD2 (23%) and SD3 (15%) treatments. Seedlings from the late SD treatments also showed better height growth and developed more shoots from dormant buds after freezing to –3 and –5oC. Collectively, these findings demonstrate the importance of proper timing of the SD treatment in relation to the seedlings’ natural growth rhythm.
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Michelle de Chantal Kjersti Holt Hanssen Aksel Granhus Urban Bergsten Mikaell Ottosson-Löfvenius Harald GripAbstract
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Aksel GranhusAbstract
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Aksel GranhusAbstract
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In this study, forest treated with different strengths of selective cutting (2570 % of volume removed) was remeasured after twelve years in 2005. At each of the sixteen 0.2 ha plots, including four repeats of each treatment, all trees larger than dbh 2.5 cm were calipered. We investigated growth, changes in stand structure, tree age, tree damage and crown condition.The diameter distribution displayed a reverse J-curve at all plots both before and after the cuttings. Twelve years later the curve is only slightly changed. Increment cores from 300 trees were taken to analyse annual growth reactions in different diameter classes. Most trees reacted with increased growth from the second or third year after the cutting.This improved growth accelerated the following six or seven years with 20-80% increase. Both small and large trees reacted, including severely suppressed trees. The initial crown volume and crown vitality after cutting is essential for the increased growth since several years are necessary to build up a larger and better crown. The relationship between increased growth and reduced volume per hectare indicates less competition between trees regarding nutrients and light after the cutting.
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Päivi Rinne Carl Gunnar Fossdal Sissel Torre Heather Danforth Aksel Granhus Gunnhild Søgaard John Einset Harald Kvaalen Øystein Johnsen Chris Van der SchootAbstract
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Paivi L.H. Rinne Carl Gunnar Fossdal Sissel Torre Heather Danforth Aksel Granhus Gunnhild Søgaard John Einset Harald Kvaalen Øystein Johnsen Christiaan van der SchootAbstract
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Lars Sandved Dalen Heather Danforth John Einset Carl Gunnar Fossdal Aksel Granhus Harald Kvaalen Nina Elisabeth Nagy Paivi Liisa Rinne Linda Ripel Sissel Torre Gunnhild Søgaard Christiaan van der SchootAbstract
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Lars Sandved Dalen H. Danforth J. Einset Carl Gunnar Fossdal Aksel Granhus Øystein Johnsen Harald Kvaalen Nina Elisabeth Nagy P. Rinne Linda Ripel S. Torre Gunnhild Søgaard C. van der SchootAbstract
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Paivi Liisa Rinne Carl Gunnar Fossdal Sissel Torre Heather Danforth Aksel Granhus Gunnhild Søgaard John Einset Harald Kvaalen Øystein Johnsen Christiaan van der SchootAbstract
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Mortality, injury and height growth of planted Picea abies (L.) Karst. were examined in a six-year period in eight stands in southeast Norway. There were four residual stand densities (shelterwoods of high, medium and low density, 25 x 25 m patch cut) combined with three scarification treatments (unscarified, patch scarification, inverting) in a split-plot design. Mortality was generally low during the experimental period, and did not differ significantly between the residual density treatments (mean=11.1%). Both survival and plant height after 6 years were improved by inverting, while patch scarification was intermediate but not significantly different from the unscarified alternative. The patch-cutting resulted in the tallest plants, while only minor differences in height growth were found between the shelterwood treatments. The frequency of injured plants after six years was not significantly affected by the treatments (mean=10.6%). The improved plant establishment with inverting in this study is in agreement with previous studies on clear-cuts.
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Establishment, survival and height growth of sown and naturally regenerated Picea abies (L.) Karst. seedlings were examined in a 6 yr period in eight stands on bilberry woodland in south- east Norway. Five harvesting treatments (shelterwoods of high, medium and low density, 253/25 m patch-cut, 503/50 m clear-cut) and three scarification alternatives (unscarified, patch scarification, inverting) were combined in a split-plot design. Establishment, survival and plant height after 6 yrs were positively affected by scarification. Significant differences between patch scarification and inverting were not observed, although mortality tended to be lower, and seedlings slightly taller, after patch scarification. Establishment after natural seedfall was least successful on the clear-cut, but more or less equal at the other stand treatments. Height growth increased with decreasing overstorey retention, while there was a tendency towards lower survival on the clear-cuts and patch-cuts. Natural regeneration in the unscarified plots was unsuccessful after 6 yrs, while the different combinations of harvesting and scarification treatments usually gave sufficient regeneration.
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Foliage nutrient concentrations of overstorey and understorey Norway spruce (Picea abies (L.) Karst.), and height growth and needle weights of understorey saplings, were studied in a seven-year period after harvest. The following treatments were applied on each of three sites five years prior to needle sampling: control with no cutting, partial cutting with 50-60 % removal of basal area, and patch cut (25 x 25 m - 0.063 ha clear-cut). Saplings on control plots had higher concentrations of K and Cu in current-year needles (C) than overstorey trees. Increased harvest intensity led to a reduction of K in C- needles and Mg in (C+1)-needles of saplings, and of B in both saplings (C, C+1) and overstorey trees (C+1). Sapling needle weights generally increased with harvest intensity, whereas no effect of foliage N status on needle weights could be detected. The growth response of saplings was explained by the interaction between foliage N status, quantified as average N concentration in C- and (C+1)-needles, and harvest intensity. The results illustrate that sufficient N supply is a key factor for the ability of advance regeneration to utilize the improved light condition associated with overstorey removal.
Authors
Aksel GranhusAbstract
The risk of logging damage to residual trees (height >3.0 m) and advance regeneration saplings (height 0.5–3.0 m) was evaluated after mechanized (single-grip harvesters + forwarders) and motor-manual (chain saw + skidding) selection harvesting in studies I and II. Harvesting took place during the winter season. Mechanized harvesting caused the highest injury rates, and the difference was highest at high cutting intensity in densely stocked stands. Another important difference between the two operating methods was the spatial distribution of the injury risk relative to striproads. The most important injuries on the larger (>3.0 m) trees were stem- and root wounds, and loss of branches. Wounds tended to be larger, and crown injuries more serious, after mechanized harvesting, but differences were not statistically significant. The most frequent injuries on saplings were crown injuries (loss of branches, stem breakage) and stem lean. In motor-manually harvested stands saplings without pre-harvest deformities in the form of top- or leader defects were more prone to damage than saplings with such defects. A similar difference was not found in stands subjected to mechanized harvesting. This result was attributed to the different work patterns during felling and processing with the two operating methods, in combination with the spatial distribution of saplings of different quality relative to larger trees and stand openings. In study III sapling mortality, and recovery from logging damage in a five-year period after selection harvesting, was investigated. Mortality on the different plots (n=11) was highly variable. For saplings without previous logging damage mortality was related to pre-harvest vigour, and increased with increasing cutting intensity in the immediate surrounding of the sapling. Unspecified site factors also contributed to explain the probability of mortality. Saplings that had been pushed over during harvesting often survived and recovered, while injuries to the crown led to poor survival. Crown injuries were most common on plots subjected to mechanized harvesting, while stem lean was correspondingly important on motor-manually harvested plots. Whether this pattern was attributed to differences in temperature at the time of harvesting (winter), or operating method, is uncertain. In study IV advance regeneration responses in terms of height growth, needle dry weights, and foliar nutrient concentrations were compared after three different release treatments: untouched control, selection harvesting with 50-60 % removal of basal area (BA50-60), and patch cut (25x25 m - 0.063 ha clear-cut). The foliar analyses were carried out five years after treatment, and included dominant and co-dominant (overstorey) trees on control and BA50-60 plots. Height growth and needle dry weights of saplings generally increased with increasing overstorey removal. The growth response was explained by an interaction of foliar nitrogen concentration in current (C) and one-year-old (C+1) needles, and degree of overstorey removal. The foliar analyses did, however, not confirm improved N status after cutting. Increasing overstorey removal led to a reduction of K (C), Mg (C+1) and B (C, C+1) in saplings. A parallel decline of B (C+1) occurred in the overstorey trees (BA50-60). Saplings on control plots had higher concentrations of K and Cu in C-needles, relative to overstorey trees. The influence of neighbour tree basal area on sapling height growth and presence of natural defects (top- and leader damage) was examined in study V. The three stands selected for the study had not been subjected to cutting for several decades, and basal areas ranged from 25–33 m2 ha-1. The relationship between growth and four basal area variables was evaluated: basal area (m2 ha-1) of taller (>3.0 m) neighbour trees within 2.82, 3.99 and 5.64 m radius from the sapling (25, 50 and 100 m2 circular plots), and basal area (m2) of trees within 5.64 m radius weighted according to distance from the sapling. A reduction of growth attributed to increasing basal area of neighbour trees was only observed for the tallest saplings (2.1-3.0 m). Between 33 and 42 % of the saplings had leader- or top defects, and damage frequencies increased with declining distance to the nearest taller neighbour tree.
Abstract
Injuries and mortality to advance growth (saplings) after selection harvesting was studied in 17 multi-storied Norway spruce (Picea abies (L.) Karst.) stands. Harvest removals ranged from 33 to 67 % of initial basal area. Four of the stands were harvested motor-manually (chain saw + skidding with farm tractors; M-FT). The remaining stands were harvested with single-grip harvesters and forwarders (H-FW). In each stand, injury rates were evaluated on a 24x48 m plot, located between the centrelines of two parallel striproads that were spaced 24 m apart. All logging teams had at least five years of experience in clear-cutting and thinning operations. The trees to be removed, and striproad centrelines, were marked prior to harvest. Mortality varied between 5 and 51 %, whereas total injury (injured + dead saplings) varied between 17 and 76 %. Mortality- and injury levels were generally highest on H-FW plots. Crown reduction and leaning stems were the most frequent types of injury, regardless of operating method. Injury rates increased with sapling height with the H-FW method, whereas the opposite was found on M-FT plots. Saplings without pre-harvest damage in the form of top- or leader defects had a higher probability of being injured than saplings with such damage in stands harvested with the M-FT method. A similar difference was not found on H-FW plots. A logistic regression model show that the spatial risk for injury depends on the interaction between forest condition factors and operational characteristics. Forest condition factors influencing the risk of injury are sapling height and the location of saplings relative to larger residual trees and striproads. Corresponding operational characteristics are operating method and harvest intensity.
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Aksel GranhusAbstract
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