Wood bark is one of the major feedstocks in bioenergy and bioeconomy scenarios in Finland. Currently it is used mainly for producing heat and power, which make buffer storage essential due to ...seasonal variations in the demand for energy. The storage of bark is associated with problems like the occurrence of self-heating, biomass losses, and the reduction of its quality as fuel. Extraction of valuable extractives from the bark before burning is an interesting option when aiming to increase the value of this side-stream. However, the content of extractives starts to decrease immediately after tree felling and this degradation continues during storage.
This study examined changes in fuel quality and extractive amounts during the storage of Norway spruce (Picea abies) bark from sawmills. The moisture content of the bark decreased five percent during the storage period of eight weeks. The temperature in the storage pile rose within one week to over 50° and there was evidence of appreciable initial biological activity within the bark. The dry matter losses of spruce bark were on average six % per month.
The content of acetone-soluble extractives decreased significantly, being 66.2% of the original amount after eight weeks’ storage. The most significant changes in extractive content occurred within the two first weeks of storage when 30% of the extractives were lost. This means that in order to utilize these valuable compounds, the material should be sent for further processing as soon as possible after debarking.
•The extractives content starts to decrease immediately after tree felling and this degradation continues during storage.•Significant changes in extractive content of spruce bark and the highest dry matter losses occurred within the 2 first weeks of storage.•It is essential to keep the period from the felling and debarking of the tree to the processing as short as possible.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Non-native Norway spruce (NS) shows a limited invasive capacity in Eastern Canada.•Most NS regeneration was found in plantation understory and edges.•Beyond the plantation edge, NS regeneration ...spread the most in open habitats.•Balsam fir could regenerate almost as NS in the understory of NS plantations.
Introduced species are used more and more for timber production throughout the world. This raises much debate about their impact on natural ecosystems. In Quebec, Canada, similar concerns are expressed regarding Norway spruce (Picea abies (L.) H. Karst.), which was introduced in the early 1900s and is currently the main non-native conifer used for planting. The purpose of the present study was to evaluate the current spread of Norway spruce in Quebec and to assess under which circumstances it can regenerate and become established. We studied Norway spruce regeneration dynamics over 5 years in the understory, edge and surroundings of 10thinned Norway spruce plantations aged 36 to 65 years. Most Norway spruce regeneration was found in the understory and near the edge of plantations, and beyond the plantation border on a few sites. Norway spruce seedling density was highly variable in the understory and at the plantation edge (0.6–30.7stems·m−2 and 0–8.5stems·m−2, respectively). Beyond the edge, high densities of Norway spruce regeneration (0.1 to 1.2 seedlings·m−2) were found in 2 recent clearcut areas and in only 2 intolerant hardwood high forests, as far as 28 m from Norway spruce plantations. Overall, Norway spruce regeneration was young (less than 16 years for 98% of seedlings) and relatively slow-growing (on average, 1.1–7.9 cm·year−1, depending on transect location and height class). Balsam fir (Abies balsamea (L.) Mill), a native species, regenerated well (mean density of 3.1stems·m−2) in the understory and the edge of 5 of the 10 studied plantations. When regeneration of both species was present, mean seedling age, growth and height were similar, but balsam fir had a better survival rate than Norway spruce (84% vs.65%). These findings suggest that Norway spruce shows a limited invasive capacity, particularly in the closed canopy of natural forests. Moreover, the presence of native balsam fir in the understory of Norway spruce plantations indicates that the successional pathway could move the stand towards a more natural ecosystem. These results can be useful to target surveys of the most sensitive ecosystems and to develop proactive management strategies.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Microscopic X-ray computed tomography (XµCT) aided finite element (FE) modelling is a popular method in material science to relate material properties to heterogeneous microstructures. Recently, a ...methodology was developed for the XµCT aided FE modelling of wood, which characterises the process from specimen preparation to estimation of material properties. In the current research, this methodology is tested on branches of Norway spruce (Picea abies (L.) Karst.) to estimate the hygroexpansion coefficients of opposite (OW) and compression wood (CW). These properties are largely unknown and have engineering implications. The study is complemented by measurements of density, moisture content (MC) and elastic moduli. Results showed that the methodology assisted in the design of an integrated process and the identification of bottlenecks. It was seen that the level of detail of the numerical model had a strong influence on the obtained hygroexpansion properties. CW from branches showed higher density and longitudinal shrinkage coefficients, and elastic moduli less affected by MC. These differences are unlikely caused by MC, but more likely by the characteristics of the microstructure.
•Dynamics of N cycling was studied under spruce logging residues on a clear cut.•Stimulated N cycling processes increased N losses via leaching and N2O production.•Amount of residues affected soil N ...cycling and losses.
This study aimed to determine the effects of Norway spruce logging residues on the early-stage dynamics of N cycling processes on a clear cut and how this is related to N losses via leaching or nitrous oxide emissions. We compared N cycling processes in soil under spruce logging residues (fresh residues 40 kg m−2) and in corresponding soil without the residues for four growing seasons on a clear-cut in southern Finland. In addition, two other sites were studied in the same region six years after clear-cutting in plots with three different amounts of spruce logging residues (0, 10, 40 kg m−2). Logging residues strongly stimulated net nitrification within the first three months after the residue treatment, and this stimulation continued over the whole study period, although NO3-N concentrations in the soil decreased. Residues increased the pH, rate of net N mineralization and microbial C-to-N ratio. N2O production in the laboratory and fluxes in the field were both studied after four growing seasons. N2O production was higher in the humus layer under the residues and originated from both autotrophic nitrification and denitrification. N2O fluxes in the field were low but were also higher in the residue-containing plots. N concentrations in percolate water were monitored for four years at the same site. Logging residues increased NO3-N and NH4-N concentrations; the highest concentrations were found during the second and third years after clear-cutting. After that the concentrations of dissolved organic N increased. Both the percolate water study at this site and the N cycling studies at the two other sites six years after clear-cutting showed that the largest amount of residues resulted in the highest rates of net N mineralization and net nitrification and the highest concentrations of mineral N forms in the percolate water. The amount and decomposition stage of the logging residues as well as the development of ground vegetation may together determine the dynamics of soil N cycling processes and losses.
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•Cascading biotic disturbances have an increasing impact in forestry.•Outbreaks were potentiated by the increasing amount of spruce.•Outbreaks increased by decreasing slope.•Ice storm affects drivers ...of bark beetle outbreaks.•Removal of dead trees alone is insufficient for preventing bark beetle outbreaks.
Large-scale disturbances in forests are becoming more frequent due to a changing climate. Biotic disturbances can have cascading effects and therefore have a significant economic impact in forestry. It is therefore important to gain an understanding of the drivers of forest pest outbreaks in epidemic situations after large-scale disturbances and the implications for forest management. We investigated the influence of drivers on the bark beetle outbreaks following a large-scale ice storm in 2014 in Slovenia. A country-wide survey was done on the variables affecting ice storm damage to spruce trees. Additionally, the influence of the drivers of bark beetle attacks on outbreak intensity was assessed and compared under epidemic and endemic situations, and the effectiveness of forest management measures was assessed. Spruce trees were either uprooted or snapped, or the crown was lightly to severely damaged. The outbreaks under endemic situations were potentiated by the increasing amount of spruce and reduced by increasing slope. After the ice storm, the amount of sanitary felling because of outbreaks increased in areas with more steeper slopes, where the ice storm took place. An increase in the level of disturbance and a higher availability of dead and weakened trees positively affected bark beetle populations. The removal of dead trees alone in the first year after the ice storm was found to be an insufficient measure for preventing bark beetle outbreaks. The ineffectiveness of current practices suggests that bark beetle management should be reconsidered with regard to large-scale disturbances. When defining measures against bark beetle outbreaks, drivers in epidemic situations should be prioritized over those that are important in endemic situations. The results imply that the known factors that affect bark beetle attacks are not necessarily the same as those that drive bark beetle attacks after extraordinary disturbance events. Mixed stands should be promoted in forests for sustainable management.
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We examined the effect of individual environmental factors on the current spruce tree growth assessed from a repeated country-level statistical landscape (incl. forest) survey in the Czech Republic. ...An extensive set of variables related to tree size, competition, site characteristics including soil texture, chemistry, N deposition and climate was tested within a random-effect model to explain growth in the conditions of dominantly managed forest ecosystems. The current spruce basal area increment was assessed from two consecutive landscape surveys conducted in 2008/2009 and six years later in 2014/2015. Tree size, age and competition within forest stands were found to be the dominant explanatory variables, whereas the expression of site characteristics, environmental and climatic drives was weaker. The significant site variables affecting growth included soil C/N ratio and soil exchangeable acidity (pH KCl; positive response) reflecting soil chemistry, long-term N-deposition (averaged since 1975) in combination with soil texture (clay content) and Standardized Precipitation Index (SPI), a drought index expressing moisture conditions. Sensitivity of growth to N-deposition was positive, although weak. SPI was positively related to and significant in explaining tree growth when expressed for the growth season. Except SPI, no significant relation of growth was determined to altitude-related variables (temperature, growth season length). We identified the current spruce growth optimum at elevations about 800ma.s.l. or higher in the conditions of the country. This suggests that at lower elevations, limitation by a more pronounced water deficit dominates, whereas direct temperature limitation may concern the less frequent higher elevations. The mixed linear model of spruce tree growth explained 55 and 65% of the variability with fixed and random effects included, respectively, and provided new insights on the current spruce tree growth and factors affecting it within the environmental gradients of the country.
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•Promoted artificial spruce distribution makes Central-European forestry vulnerable.•Observed tree growth available from a repeated national survey (2009–2015)•Mixed linear model used to assess significant environmental variables for growth.•Spruce tree growth linked to soil properties, N-deposition and moisture conditions•Altitudinal range reflects indirect and direct limitation to tree growth.
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•Disturbance legacies persist for decades in a temperate forest landscape.•Simulated carbon loss from a disturbance was compensated during 18–29 years.•An enhanced carbon sink following a disturbance ...may support forest recovery in temperate landscapes.•Warmer and drier climate slows down the recovery under climate change.•CO2 fertilization is prominent in the forest carbon recovery under climate change.
Disturbances alter composition, structure, and functioning of forest ecosystems, and their legacies persist for decades to centuries. We investigated how temperate forest landscapes may recover their carbon (C) after severe wind and bark beetle disturbance, while being exposed to climate change. We used the forest landscape and disturbance model iLand to quantify (i) the recovery times of the total ecosystem C, (ii) the effect of climate change on C recovery, and (iii) the differential factors contributing to C recovery. We reconstructed a recent disturbance episode (2008–2016) based on Landsat satellite imagery, which affected 39% of the forest area in the 16,000 ha study landscape. We subsequently simulated forest recovery under a continuation of business-as-usual management until 2100.
Our results indicated that the recovery of the pre-disturbance C stocks (C payback time) was reached 17 years after the end of the disturbance episode. The C stocks of a theoretical undisturbed development trajectory were reached 30 years after the disturbance episode (C sequestration parity). Drier and warmer climates delayed simulated C recovery. Without the fertilizing effect of CO2, C payback times were delayed by 5–9 years, while C parity was not reached within the 21st century. Recovery was accelerated by an enhanced C uptake compared to undisturbed conditions (disturbance legacy sink effect) that persisted for 35 years after the disturbance episode.
Future climate could have negative impacts on forest recovery and thus further amplify climate change through C loss from ecosystems, but the effect is strongly contingent on the magnitude and persistence of alleviating CO2 effects. Our modelling study highlights the need to consider both negative and positive effects of disturbance (i.e., C loss immediately after an event vs. enhanced C uptake of the recovering forest) in order to obtain a comprehensive understanding of disturbance effects on the forest C cycle.
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Climate controls forest biomass production through direct effects on cambial activity and indirectly through interactions with CO2, air pollution, and nutrient availability. The atmospheric ...concentration of CO2, sulfur and nitrogen deposition can also exert a significant indirect control on wood formation since these factors influence the stomatal regulation of transpiration and carbon uptake, that is, intrinsic water use efficiency (iWUE). Here we provide 120-year long tree-ring time series of iWUE, stem growth, climatic and combined sulfur and nitrogen (SN) deposition trends for two common tree species, Pinus sylvestris (PISY) and Picea abies (PCAB), at their lower and upper distribution margins in Central Europe. The main goals were to explain iWUE trends using theoretical scenarios including climatic and SN deposition data, and to assess the contribution of climate and iWUE to the observed growth trends. Our results showed that after a notable increase in iWUE between the 1950s and 1980s, this positive trend subsequently slowed down. The substantial rise of iWUE since the 1950s resulted from a combination of an accelerated increase in atmospheric CO2 concentrations (Ca) and a stable level of leaf intercellular CO2 (Ci). The offset of observed iWUE values above the trajectory of a constant Ci/Ca scenario was explained by trends in SN deposition (all sites) together with the variation of drought conditions (low-elevation sites only). Increasing iWUE over the 20th and 21st centuries improved tree growth at low-elevation drought-sensitive sites. In contrast, at high-elevation PCAB sites, growth was mainly stimulated by recent warming. We propose that SN pollution should be considered in order to explain the steep increase in iWUE of conifers in the 20th century throughout Central Europe and other regions with a significant SN deposition history.
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•Rising CO2 and climate warming triggered increase in water-use efficiency (iWUE).•Interactions between iWUE, N and S deposition, and tree growth were investigated.•iWUE trends were predicted by combined effects of S and N deposition and drought.•Increasing iWUE accelerated tree growth at low-elevation sites.
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•A soil warming experiment in a Norway spruce stand for 476 days was performed.•Warming negatively influenced the stability of the soil organic matter.•Simulated warming increased ...dissolved organic carbon and nitrogen concentrations.•Warming increased soil pH and ammonium nitrogen of the soil organic matter.•The changes may contribute to reduced resilience of Norway spruce stands to warming.
The present-day decline observed in Norway spruce stands in the Western Carpathians is particularly worrying given the large forest area of this species. Relatively little attention has been paid to the contribution of soil chemistry to the Norway spruce decline in the context of global warming. We conducted a field experiment to simulate warming for almost 500 days in the Western Carpathians, in a mature Norway spruce stand. Soil samples were collected approximately every 3 months from the organic and mineral topsoil horizons. Total carbon, total nitrogen, pH, dissolved organic carbon (DOC), total dissolved nitrogen (TDN), nitrate (NO3-N), and ammonium (NH4-N) nitrogen concentrations were estimated. Warming caused increase in DOC, TDN, NH4-N, and pH in organic horizon, as well as increased pH in mineral topsoil. A trend for increasing total carbon and total nitrogen concentrations in the warmed organic horizon was observed. Increased concentrations of DOC and TDN may be associated with decrease in SOM stability or increase in production of biomass of the understory vegetation or soil microbial activity. Increased pH in warmed soil may be associated with the increased NH4-N and may contribute to the decrease in soil ability to adsorb DOC. We conclude that soil warming negatively stimulates soil organic matter stability, resulting in higher concentrations of easy migrating labile forms, mostly organic acid anions. Observed changes may contribute to the deterioration of Norway spruce stands.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
