Live storage and drying of storm-felled Norway spruce (Picea abies,L. Karst.) and Scots pine (Pinus sylvestris L.) trees

Storm-felled trees left in the forest for a shorter or longer period, affect the quality of the logs. The change in quality is mainly because of attack of fungi and insects, which in turn depends on the moisture content (MC) of the sapwood. The purpose of this study was to receive more knowledge about drying of storm-felled trees by investigating how fast winter storm-felled Norway spruce and Scots pine dried when left in the forest. Sixteen storm-felled spruces with part of the roots still in ground contact were selected from three stands and in addition to 10 pines from one of the stands. The trees were examined for MC in the sapwood until 21 months after the storm. This study indicates that wind-thrown trees with roots still connected to the soil can survive one summer without any value loss caused by draught, fungi and insects. The stand conditions can be of importance as the storm-felled trees in the stand, with scattered windthrow, were in best condition after one year, as they were shadowed by the trees still standing. Comparing spruces and pines with the stand with scattered windthrow, pines were more sensitive to drought and reached critical MC earlier.     

Outdoor exposure of untreated Scots pine (Pinus sylvestris L.) and Norway spruce [Picea abies (L.) Karst.] wood samples

Abstract

Untreated Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) samples were exposed above ground in a durability test for 6 years. The samples consisted of three pieces of wood, 22×95×500 mm, screwed together; two pieces lengthwise with a third piece overlapping. Weight was measured, to calculate moisture content (MC), and samples checked regularly for cracks and fungal growth. Parameters investigated were heartwood/sapwood (pine), annual ring orientation (spruce), stand site, annual ring width and density. Stand site, annual ring width and density had no influence on MC or fungal growth for either pine or spruce. Spruce samples with vertical annual rings had fewer cracks than samples with horizontal annual rings. Pine sapwood samples had a high MC and a large amount of rot fungi, while heartwood had a lower MC and no rot. Most spruce samples were similar to pine heartwood, except from a few samples that had high MC and fungal growth. Those were all sawn from the outer part of the log. Therefore, it can be stated that spruce sawn from the inner part has almost the same properties as pine heartwood, while spruce from the outer part of the log has similar properties to pine sapwood.     

Superoxide dismutase (SOD) activity in Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies L. Karst.) needles in northern Finland

The superoxide dismutase (SOD EC 1.15.1.1) activity in Scots pine (Pinus sylvestris) and Norway spruce (Picea abies L. Karst.) needles in urban and rural trees of northern Finnish populations was studied. Enzyme activity was higher in pine than in spruce needles. Two pine clones from eastern Finland and Lapland revealed great differences in specific SOD enzyme activity.     

Estimating foliage biomass in Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) plots

Dynamic decomposition models are needed to estimate changes in the carbon stock of boreal soil because these changes are difficult to measure directly. An important aboveground carbon flux to the soil is foliage litterfall. To estimate this flux, both the amount and the turnover rate of the foliage biomass component must be known. Several methods for estimating foliage biomass of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.), including biomass equations and biomass expansion factors (BEFs), were compared with predicted foliage biomass based on forest inventory plot-level measurements. Measured foliage biomass was up-scaled from the branch-level to the plot-level by combining forest inventory variables (diameter, height, height at the crown base and crown base diameter) based on the assumptions of pipe model theory. Combining the foliage biomass: cross-sectional area ratio with the forest inventory variables provided accurate estimates of foliage biomass at the plot-level for plots in southern Finland. The results emphasize the need to test biomass equations with independent data, especially when the equations applied are based on neighboring regions.     

Presence of longitudinal cracks in planks from storm-felled pine (Pinus sylvestris L.) and spruce (Picea abies (L.) Karst.)

Abstract

After the severe storm Gudrun in southern Sweden in 2005, a quantitative study was done in order to investigate the presence of lengthwise crack on planks taken from storm-felled trees in southern Sweden, compared to planks from standing trees not subjected to this storm (central Sweden). The main yield from each log was examined. In total, 1087 pine (Pinus sylvestris) planks and 3626 spruce (Picea abies) planks from the storm-struck area were investigated and compared to 1953 spruce and 2000 pine planks from trees outside the storm-struck area. The examination of cracks was done visually on dried planks. For pine, 51.7% of the planks from storm-felled trees had a total length longer than 0.5 m, compared to 7.3% for the reference material. As for spruce, 11.0% of the planks from storm-felled trees had a total crack length of more than 0.5 m, compared to the reference material where 2.2% had cracks longer than 0.5 m. The results show that the storm-felled trees had more longitudinal cracks than the reference material and that pine was more likely to develop storm-related cracks than spruce.     

Some factors influencing susceptibility to discoloring fungi and water uptake of Scots pine (Pinus sylvestris), Norway spruce (Picea abies) and Oriental spruce (Picea orientalis)

Abstract

The heartwood and sapwood from Scots pine (PS), Norway spruce (PA), and Oriental spruce (PO) were tested for susceptibility to discoloring fungi and water uptake. In addition, annual ring width and density were measured. The methods used were Mycologg for testing growth of fungi and a modified version of EN 927-5 to investigate water uptake. For pine, the heartwood showed a lower water uptake and no discoloring fungi growing in the tests. The heartwood had a significantly higher density and smaller annual ring width than the sapwood. In PA the heartwood had significantly lower discoloration than sapwood. The total water uptake in g/m² was significantly higher in sapwood, but not the calculated moisture content. As for wood properties, the density was significantly higher in sapwood compared to heartwood, although there were no differences in annual ring width. Regarding PO, differences in water uptake could be seen between sapwood and heartwood although the densities were similar. These results show that susceptibility to discoloring fungi and water uptake is hard to correlate to a single inherent property when looking at different wood species.     

Cadmium uptake in Norway spruce (Picea abies (L.) Karst.) seedlings

Root elongation of Norway spruce (Picea abies (L.) Karst.) seedlings was inhibited in the presence of 5 microM Cd, but was unaffected by a Cd concentration at 0.05 microM. Nutrient solutions labeled with (109)Cd were used to investigate the influence of pH, cations and the metabolic inhibitor 2,4-dinitrophenol (DNP) on the uptake of Cd by roots of intact spruce seedlings. Extracellular Cd was removed by washing the roots, and the relative amounts of Cd in the root apoplast and symplast estimated. In the presence of DNP, Cd uptake was reduced at 0.05 microM (non-toxic) but not at 5 microM Cd (toxic). At 0.05 microM Cd, the uptake of Cd into both the apoplast and symplast was dependent on the pH of the nutrient solution. Lower pH decreased Cd accumulation. Aluminum supplied at 100 or 500 microM lowered the Cd concentrations of both the apoplast and symplast. An increase in Ca or Mg supply reduced the Cd concentration of the apoplast but not of the symplast. In the presence of 5 microM Mn, the concentration of Cd in the symplast decreased by 44% compared to the control (1 microM Mn). High concentrations of Zn or Hg did not affect the Cd concentration of the roots.     

Crown architecture and stemwood production in Norway spruce (Picea abies (L.) Karst.)

The morphological data for Norway spruce (Picea abies (L.) Karst.) trees published by Burger (1953) were reanalyzed to examine the relationships between crown shape, needle and branch mass density of crown volume, needle efficiency in stemwood production, harvest index and stemwood production efficiency per unit of crown projected area. Production of stemwood per unit of crown projected area was higher in narrow-crowned trees than in broad-crowned trees because the narrow-crowned trees had (i) smaller horizontal space requirements for equal crown volumes, (ii) higher leaf area index due to both the geometrical crown shape and higher needle density per unit of crown volume, and (iii) higher harvest index indicating high allocation of dry matter production to stem.     

Cupping of wooden cladding boards in cyclic conditions—a study of boards made of Norway spruce (Picea abies) and Scots pine sapwood (Pinus sylvestris)

The aim of the study was to examine how the thickness and species of softwood influence cupping during cyclic conditions. The study was conducted with full-scale test walls in laboratory conditions. On the basis of the results, the thickness and species of softwood both have a significant influence on cupping of the cladding board. The boards made of Norway spruce were considerably more resistant to cupping than those made of Scots pine sapwood. Boards made of Scots pine sapwood were more likely to remain curved after each drying period. It appears probable that the cupping sensitivity of Scots pine sapwood affects the durability of the cladding, e.g., causing cracking formation on the surface and peeling of the coating. From the curving results, it is possible to estimate surface elongation and durability of the wood surface and of the coating in cyclic conditions.     

Current growth differences of Norway spruce (Picea abies), Scots pine (Pinus sylvestris) and birch (Betula pendula and Betula pubescens) in different regions in Sweden

Abstract

The choice of species in forestry is important, and a real issue as large areas of wind-damaged forest land in southern Sweden need to be regenerated. To compare the growth potential between the most common tree species in Sweden, ratios between site quality derived from site index values determined with site properties were used. A regression function to determine site index for birch from site properties was used to complement the known relationships between site properties and site index for spruce and pine. In large regions of Sweden the distribution of site quality classes was calculated to compare the special characteristics and demands of the three species. On average, the growth difference for pine compared to spruce was about 60% in southern Sweden and 95% in northern Sweden. Corresponding figures between birch and spruce were 40% and 60%. Birch was expected to produce around 60% of pine in northern Sweden and about 70% in southern Sweden. However, it must be stressed that the comparison is based on survey data encompassing mainly naturally regenerated birch, whereas spruce and pine are mainly planted.     

A model describing natural regeneration recruitment of Norway spruce (Picea abies (L.) Karst.) in Austria

In the absence of reliable and representative data on the frequency of seed years, seed amounts, germination and survival of seeds, the data of the observation period 1992–1996 of the permanent national forest inventory of Austria are used to develop a model describing the probability for the occurrence, density and height of Norway spruce (Picea abies (L.) Karst) natural regeneration in the forests of Austria. The forest inventory provided data on natural regeneration (saplings between 10 and 130 cm height) on clusters within a 3.89 km square sampling grid. A logistic equation is used to predict the probability for natural regeneration occurrence. Input parameters for this equation are the variables that describe the site, with slope and azimuth as continuous variables, and growth districts and vegetation types as discrete variables; the crown competition factor describes density and the quadratic mean diameter describes the stage of development of the stand. The same equation type is used to predict the probability for the occurrence of Norway spruce, conditional on the occurrence of some regeneration. An additional variable in this species specific model is a dummy variable which is set to 1 if Norway spruce occurs in the overstory and otherwise zero. Additional site variables entering this model are elevation and vegetation types characterizing soil fertility and moisture. Because the density and height of spruce regeneration depends on the stand's susceptibility to browsing, the probability for browsing is also modelled as a logistic equation depending on elevation, vegetation type, and stand density. Finally the probability distribution for height and density of the regeneration is described by two bivariate Weibull-distributions, each one describing browsed and unbrowsed Norway spruce regeneration respectively.     

Moisture sorption and swelling of Norway spruce [Picea abies (L.) Karst.] impregnated with linseed oil

Abstract

The moisture sorption and swelling of spruce specimens impregnated with linseed oil and unimpregnated controls were studied in two sorption experiments: from 0 to 55% relative humidity (RH) and from 55% RH to water saturation. Sorption isotherms were also determined using a sorption balance. The impregnated specimens had lower rates of both moisture sorption and swelling than the unimpregnated controls; however, there was no significant difference in final moisture contents. In addition, the linseed oil impregnation did not improve the dimensional stability of the wood; in most cases the specimens impregnated with linseed oil swelled more than the unimpregnated controls. For the impregnated specimens, reductions in swelling rates were in most cases seen without corresponding reductions in final swelling. The moisture sorption rate was reduced for the impregnated specimens but there were generally no reductions in equilibrium moisture content.     

Microclimate and moisture content profile measurements in rain exposed Norway spruce (Picea abies (L.) Karst.) joints

In order to perform service life predictions of rain exposed wood structures, the moisture and temperature conditions in the structure need to be known as well as which degradation that occurs under those exposure conditions. The microclimate (the moisture conditions at the surface) is the boundary condition for moisture transport into the wood and depends on the detail design; joints between two pieces of wood can act as a water trap which give long durations of surface moisture after rain events and hinders drying. This study presents moisture content and microclimate measurements in three types of Norway spruce joints exposed to artificial rain in the laboratory. Both the microclimate (the duration of water on surfaces and in gaps) and the moisture content profiles were monitored. The microclimate was changed by changing the size of the gap between the two boards. The duration of water in the gap depended both on the gap size and on the permeability of the wood (sapwood/heartwood, end grain surface/side grain surface). In many cases, a larger gap width gave shorter durations of high moisture contents since a larger gap gave more favourable drying conditions, but the magnitude of this reduction varied between joint types.     

Climate-sensitive modelling of site-productivity relationships for Norway spruce (Picea abies (L.) Karst.) and common beech (Fagus sylvatica L.)

The aim of the presented research project is to fit a site index model capable for predicting changes in site-productivity in a changing climate. A generalized additive model is used to predict site index as a function of soil and climate variables. The climate parameter values are estimated using the regional climate model WETTREG, based on global climate simulations with the global circulation model ECHAM5/MPI-OM for the reference period from 1961 to 1990. The climate values are further regionalized on a 200 m × 200 m grid. The generalized additive model quantifies the partial linear and non-linear effects of the predictor variables on site index. The model is parameterized for Norway spruce (Picea abies (L.) Karst.) and common beech (Fagus sylvatica L.) in Lower Saxony, Germany. Two case studies investigate the model's ability to generate information in order to support forest management planning decisions under a changing climate. One example analyzes the possible shift in site index of spruce along a precipitation gradient under the International Panel on Climate Change (IPCC) emission scenario A1B in the period from 2041 to 2050. The other case study shows possible future changes in site index of beech along a temperature gradient.     

Bioenergy production and soil conservation from Norway spruce (Picea abies L. Karst) plantations in Denmark

This study analyses the trade-off between bioenergy production and soil conservation through thinning operations in Norway spruce (Picea abies L. Karst) plantations in Denmark. Thinning operations were evaluated under different regimes and intensities for a complete rotation period of sixty years and for different site qualities (site-classes I–VI). Applying a dynamic forest growth modeling tool, evolution of forest structure was predicted to observe the potentials for biomass production and inevitable soil degradation. Results showed thinning from below, with a higher utilization (maintenance of a minimum basal area of 25 m² ha^?1) could produce more bioenergy. However, these operations require simultaneous severe forest soil degradation. Therefore, the optimum thinning for bioenergy production under preservation constraints was thinning from above with a lower intensity (maintenance of a minimum basal area of 45 m² ha^?1). The ratio of bioenergy win (kWh) to soil-loss (m³ ha^?1) was calculated for this regime varying between 74,894 kWh m^?3 in a high quality site (site-class I) and 6,516 kWh m^?3 in a low quality site (site-class VI) with an average of 44,282 kWh m^?3. However, this could not always preserve the highest amount of growing stock essential for natural dynamics of forest ecosystem with an exception of the low quality sites (site-class VI). Thus, when aiming at bioenergy production through thinning operations, trade-offs with soil conservation and growing stock preservation should be regarded to prevent environmental degradation.     

Impregnation of Norway spruce (Picea abies L. Karst.) wood by hydrophobic oil and dispersion patterns in different tissues

Wood from Norway spruce (Picea abies L. Karst.) is biologicallydegraded in exposed conditions. It also has anatomical featuresthat make it difficult to impregnate with preservatives by currentlyavailable industrial processes. In the study reported here,we used the new Linotech process to impregnate Norway sprucewood with hydrophobic linseed oil and then quantified its uptakeand dispersal in anatomically distinct wood tissues. We alsoinvestigated the effects of the wood moisture content on theresults of the impregnation. Samples (500 x 25 x 25 mm) weretaken from 15 trees in a coniferous forest in northern Sweden(64° 10' N, 160–320 m a.s.l.). The parameters forthe Linotech process were 2–3 h treatment time at 0.8–1.4MPa and 60–140°C. To determine the level of uptake,the linseed oil was extracted from the impregnated wood usingmethyl-tertiary-butyl-ether. The uptake was quantitatively analysedby comparing X-ray microdensitometry values obtained followingimpregnation both before and after oil removal. In earlywood,initial moisture content had an obvious effect on the impregnationresult. Six times more oil was taken up when the moisture contentwas greater than ~150 per cent than when it was less than 30per cent. Theoretical calculations, based on density levels,suggest that the water-filled porosity of the wood (water volumedivided by porosity volume) was positively correlated with thelinseed oil uptake, and more strongly correlated in earlywoodthan in latewood. There were also significant differences inuptake between different wood tissues; heartwood/mature woodand heartwood/juvenile wood showed 10–20 per cent weightincreases due to linseed oil uptake, compared with 30–50per cent in sapwood/mature wood. Examination by scanning electronmicroscopy confirmed these uptake patterns. The moisture contentafter impregnation was about 5 per cent, irrespective of theLinotech process parameters, tissue type and initial moisturecontent. In conclusion, the impregnation process used here resultsin high levels of well-dispersed linseed oil uptake and shouldfacilitate drying.     

End grain water absorption and redistribution in slow-grown and fast-grown Norway spruce (Picea abies (L.) Karst.) heartwood and sapwood

Abstract

Wood is susceptible to decay by rot fungi if it is exposed to high-moisture contents during long periods of time and it is therefore important to limit the duration of such periods. Critical points in outdoor wood structures are, for example, end grain surfaces in joints where water can get trapped after a rain. It is therefore of interest to study both absorption and redistribution of moisture in wood. This paper presents moisture content profiles during end grain water absorption and redistribution in Norway spruce (Picea abies (L.) Karst.) measured by computed tomography with the specimens in individual climate boxes. Heartwood and sapwood of two provenances (slow-grown and fast-grown wood) were included. No major differences were seen between the water uptake of the slow-grown and the fast-grown wood since the densities were similar despite of the large difference in growth ring width. However, for the sapwood specimens, the moisture content was higher further into the specimens than for the heartwood specimens in agreement with previous studies. For the slow-grown wood, the redistribution was also generally more rapid for the sapwood specimens than for the heartwood specimens.     

Recovery of photosynthesis in 1-year-old needles of unfertilized and fertilized Norway spruce (Picea abies (L.) Karst.) during spring

Photosynthetic O(2) evolution and chlorophyll a fluorescence were measured in 1-year-old needles of unfertilized and fertilized trees of Norway spruce (Picea abies (L.) Karst.) during recovery of photosynthesis from winter inhibition in northern Sweden. Measurements were made under laboratory conditions at 20 degrees C. In general, the CO(2)-saturated rate of O(2) evolution was higher in needles of fertilized trees than in needles of unfertilized trees over a wide range of incident photon flux densities. Furthermore, the maximum photochemical efficiency of photosystem (PS) II, as indicated by the ratio of variable to maximum fluorescence (F(V)/F(M)) was higher in needles of fertilized trees than in needles of unfertilized trees. The largest differences in F(V)/F(M) between the two treatments occurred before the main recovery of photosynthesis from winter inhibition in late May. The rate of O(2) evolution was higher in needles of north-facing branches than in needles of south-facing branches in the middle of May. Simultaneous measurements of O(2) exchange and chlorophyll fluorescence indicated that differences in the rate of O(2) evolution between the two treatments were paralleled by differences in the rate of PS II electron transport determined by chlorophyll fluorescence. We suggest that, during recovery of photosynthesis from winter inhibition, the balance between carbon assimilation and PS II electron transport was maintained largely by adjustments in the nonphotochemical dissipation of excitation energy within PS II.