Sapwood Moisture Content Research Articles

Xylem porosity, sapwood characteristics, and uncertainties in temperate and boreal forest water use

Sapwood characteristics, such as sapwood area as well as thermal and hydraulic conductivity, are linked to species-specific hydraulic function and resource allocation to water transport tissues (xylem). These characteristics are often unknown and thus a major source of uncertainty in sap flow data processing and transpiration estimates because bulk rather than species-specific values are usually applied. Here, we analyzed the sapwood characteristics of fifteen common tree species in eastern North America from different taxonomic (i.e., angiosperms and gymnosperms) and xylem porosity groups (i.e., tracheid-bearing, diffuse- or ring-porous species) and we assessed how uncertainties in sapwood characteristics involved in sap flow calculations are propagated in tree water use estimates. We quantified their sapwood area changes with stem diameter (allometric scaling) and thermal conductivity. We combined these measurements with species-specific values of wood density and hydraulic conductivity found in the literature and assessed the role of wood anatomy in orchestrating their covariation. Using an example sap flow dataset from tree species with different xylem porosity, we assessed the sensitivity of tree water use estimates to sapwood characteristics and their interactions. Angiosperms (ring- and diffuse-porous species), with specialized vessels for water transport, showed a steeper relationship (scaling) between tree stem diameter and sapwood area in comparison to gymnosperms (tracheid-bearing species). Gymnosperms (angiosperms) were characterized by lower (higher) wood density and higher (lower) sapwood moisture content, resulting in non-significant differences in sapwood thermal conductivity between taxonomic and xylem porosity groups. Clustering of species sapwood characteristics based on taxonomic or xylem porosity groups and constraining these parameters could facilitate more accurate sap flow calculations and tree water use estimates. When combined with an increasing number of sap flow observations, these findings should improve tree- and landscape-level transpiration estimates, leading to more robust partitioning of terrestrial water fluxes.

The Effect of Crown Social Class on Bark Thickness and Sapwood Moisture Content in Norway Spruce

The research study examined the effect of tree properties (crown social class, diameter at breast height (DBH), and tree height) on bark thickness (BT) and sapwood moisture content (SMC) in Norway spruce (Picea abies (L.) H. Karst.). Both examined variables were shown to be positively affected by DBH and tree height. The relationship between DBH and SMC varied among crown social classes, while the relationship between DBH and BT was relatively constant across crown social classes. Crown social class had a relatively small effect on BT and SMC, having a more pronounced effect on SMC than on BT. The relationship between tree height and BT did not vary across crown social classes, while the relationship between SMC and tree height was found to change slightly across crown social classes. Measurements of BT and SMC in the field are affordable, fast, and easy to use. Both variables could potentially be used to improve predictions of bark beetle attacks, as they reflect the physiological state of an individual tree.

Mapping quantitative trait loci for growth and wood property traits in Cryptomeria japonica across multiple environments

Genomic regions which affected tree growth and wood property traits were investigated in the major plantation tree of Japan, Cryptomeria japonica, in three replicated common garden experiments planted in contrasting environments in Kyushu and Honshu, Japan. Phenotypic traits measured were stem diameter at breast height, tree height, wood strength (Young’s modulus), heartwood density, sapwood density, heartwood moisture content, and sapwood moisture content. Quantitative trait locus (QTL) analysis identified an average of 53 QTLs across the three environments. There were two QTLs which affected the same traits across all three environments. These stable QTLs were identified as being associated with sapwood density and Young’s modulus and explained 3.5–11.3% and 2.1–18.7% of the total genotypic variation, respectively. In contrast, the majority of QTLs detected were unique to only one environment, a finding which is consistent with QTL mapping studies of other forest trees, indicating a substantial contribution of environmental effects on the mapping progenies. Nonetheless, the two stable QTLs identified in this study could be important genomic regions to target for further research aimed at maximizing breeding efficiency and wood quality of C. japonica across wide environmental gradients.

Field Measurements of Moisture Content in Black Spruce Logs with Unilateral Magnetic Resonance

Abstract The development of portable unilateral magnetic resonance (UMR) devices permits nondestructive characterization of wood moisture content (MC) in the field. In this study, six Picea mariana Mill. logs were measured. UMR measurements of MC were taken in four different spots displaced 15 cm from the end of each log. UMR measurements were also taken at the midpoint longitudinally for three of the six logs. The end goal of this study was to demonstrate a viable approach to estimating the whole-sample MC in the field. In the case of the species studied, there is a significant difference in MC between sapwood and heartwood regions. The sapwood MC is approximately three times greater than the heartwood MC. However, the volume of heartwood is greater than sapwood in wood logs. The sapwood region contains most of the water; therefore a measurement in the sapwood, coupled with sapwood-to-heartwood volume proportions and an estimate of heartwood MC, provide a viable estimate of bulk MC of logs. Results indicate that both measurement spots (15 cm displaced from the end and at the midpoint longitudinally) give good predictions of log MC. The UMR measurement signal-to-noise ratio decreases and variability in the total sapwood signal of the four spots, displaced 15 cm from the end, increases as drying progresses. The increase in variability is because of the appearance of a drying front at some measurement spots. The UMR device and technique provide a good tool to measure MC of logs in the field.

兴安落叶松中水分、多糖和单宁的动态分布

采用超声辅助提法从兴安落叶松原料中提取糖类和单宁，考察了兴安落叶松树木的不同部位中糖类和单宁的含量差异。进而得出糖类和单宁等成分在兴安落叶松中的分布情况。结果表明：横向含水率边材较少，树皮的含水率其次，而心材的含水率较多，尤其是靠近髓的部位含水率最多；纵向含水率由树木的根部至上依次减少(8%~13%)。横向糖类物质的含量心材的外侧靠近边材的部位最多，边材其次，心材靠近髓的部位含量更少。纵向糖类物质的含量随高度的增加而增多，在6米处达到最高，之后随高度的增加含量变化不明显。单宁物质多集中分布于树皮和边材中，树皮中含量大约为边材含量的4~5倍，纵向单宁的含量随高度的增加而增多，在10~12米处达到最高，之后随高度的增加含量略有降低。 Ultrasonic-assisted extraction technology was applied for extracting saccharides and tannin from Larix gmelinii. The content differences of saccharides and tannins in different parts of Larix gmelinii were simultaneously investigated and then the detailed distribution of saccharides and tannin was obtained. Results showed that the transverse moisture content of sapwood is the lowest, followed by bark, and the heartwood is very high, especially the part nearby the pith which is the most abundant. The longitudinal moisture content of Larix gmelinii decreased in turn from the roots to trunk (8% - 13%). The transverse saccharides content in Larix gmelinii in the outside heartwood nearby the sapwood is the highest, followed by the sapwood and that of the heartwood close to the pith is the lowest. The longitudinal saccharides content increased with the increase of the height and reached the highest at 6 meters high; after that it changed not significantly with the increasing of the height. The content of tannins mainly distributed in the bark and sapwood and the content in bark was about 4 - 5 times that of the sapwood. The longitudinal tannins content increased with the increase of the height and reached the highest at 10 - 12 meters, and then it slightly reduced with the further increasing of height.

Submersion as a tactic to prevent emergence of emerald ash borer Agrilus planipennis from black ash logs

Abstract Black ash (Fraxinus nigra Marshall) trees are an important cultural resource and provide the wood used for traditional contemporary basketry by numerous Native American and First Nation tribes in the U.S.A. and Canada. The invasion and subsequent spread of emerald ash borer Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) threatens the ash resource in North America and the basketry tradition. Submersion of infested ash logs has been proposed as a potential tactic to control A. planipennis emergence, although the duration of submergence required to prevent adult beetle emergence is unknown. We assessed the survivorship of A. planipennis prepupae through adult beetle emergence in green ash (F. pennsylvanica Marshall) bolts submerged at weekly intervals for up to 6 weeks and in black ash bolts submerged at 4‐week intervals for up to 24 weeks. The moisture content of sapwood at depths where prepupal chambers are commonly found was quantified in the black ash bolts after 0, 12 and 24 weeks of submergence. Mortality of A. planipennis from prepupa to adult was low (5.7 ± 2.3%) for the first 6 weeks of submersion but rapidly increased to 100% in green ash and black ash bolts submerged for 8 weeks or longer. In black ash, the outer 1.3 cm of wood became highly saturated after submersion for 12 weeks (81.0 ± 4.5%) and moisture increased only slightly after 24 weeks (83.9 ± 2.8%). The results obtained in the present study indicate that A. planipennis prepupae in green ash and black ash bolts can survive complete submersion for extended periods of time (i.e. at least 6 weeks) and successfully emerge as adults afterwards. Logs submerged for at least 8 weeks, however, produced no live A. planipennis beetles, indicating that submersion represents an efficacious control option.

Predicting sapstain and degrade in fallen trees following storm damage in a Pinus radiata forest

Storm damage in production forests constitutes a major source of economic loss world wide, yet the retrieval of salvageable timber remains problematic. In particular, an inability to anticipate when sapstain and degrade will appear hampers the planning of log recovery operations. A study was conducted to monitor the deterioration of fallen trees following two winter storms causing wind and snow damage in a Pinus radiata plantation forest in the upper South Island of New Zealand. Percentage sapstain, incidence of basidiomycete decay fungi, and frequency of bark beetle infestation increased, while percentage sapwood moisture content decreased, over a period of 1 year. These changes proceeded more rapidly in fallen trees that were severed at stump height, to simulate breakage, than in those that were left partially rooted. There was little beetle activity at the time of the storms, but Arhopalus ferus (Coleoptera: Cerambycidae), and Hylastes ater, Hylurgus ligniperda and Pachycotes peregrinus (Coleoptera: Curculionidae: Scolytinae), were collected in flight traps during the following spring and summer. The predominant fungal species associated with sapstain was Diplodia pinea, while Ophiostoma piceae and Grosmannia huntii were isolated near the end of the period. The main decay fungi obtained were Phlebiopsis gigantea, Stereum sanguinolentum, and Schizophyllum commune. A generalized linear mixed model was constructed to predict the development of sapstain in fallen trees for conditions prevailing during the study after a storm at the same time of year. According to the model, a 10m long butt log of 22cm mid length diameter will have minimal stain (<10% of the cross sectional area affected) when cut from severed stems up to 4 months after the storm; if taken from still-rooted trees this period will extend to 1 year. However, because of large between-tree variation, economically productive log recovery will also depend on the proportion of trees that lie below an acceptable sapstain threshold. Further research is needed to determine regional and seasonal influences on the development of sapstain in fallen trees.

Sapwood moisture-content measurements in Pinus sylvestris sawlogs combining X-ray and three-dimensional scanning

Because today's sawmill processes are not fully adapted to the variability of the raw material, it is crucial to sort sawlogs according to material properties in order to process the wood efficiently and to obtain high-quality end-products. One material property that could be used for sorting is the moisture content (MC) of the sapwood, an important parameter for both the processing and the end-products. Most sawmills use three-dimensional (3D) scanners to sort logs and some have also invested in X-ray scanners. Previous studies have shown that, by combining raw data from 3D and X-ray log scanners, green sapwood density and dry heartwood density in Scots pine sawlogs can be estimated. In this study, the method was used to estimate sapwood MC in green logs. It was found that the MC estimate could be used to separate the logs into groups with high and low MC, correctly classifying all logs with MC below 100% as low MC logs. Out of all logs, 70% were correctly classified. The MC estimate could also be compared to the dry density-dependent maximum MC and used to identify logs that have actually started to dry.

Variation in pathogenicity of a mountain pine beetle–associated blue-stain fungus, Grosmannia clavigera, on young lodgepole pine in British Columbia

Grosmannia clavigera is the most pathogenic blue-staining fungal associate of the mountain pine beetle (Dendroctonus ponderosae). In contrast to its importance as a primary invader of lodgepole pine (Pinus contorta) sapwood, intraspecific variability in pathogenicity of G. clavigera on lodgepole pine, the predominant host of mountain pine beetles in British Columbia, has not been investigated in detail. The present work reports on pathogenicity indicators induced by five G. clavigera isolates inoculated into lodgepole pines and growth characteristics of the isolates on artificial media. Fungi were inoculated at 200 inoculations/m2 into young lodgepole pine trees. Phloem lesion length, sapwood occlusion area, and sapwood moisture content were measured after 7 or 48 weeks. Three isolates produced long lesions, occluded larger areas, and reduced more the moisture content after 48 weeks compared with the remaining two isolates. Isolate ATCC 18086 induced the strongest pathogenic symptoms after 7 weeks and grew the fastest up to 22.5 °C but grew the slowest at 27.5 °C. In a low-oxygen environment, most isolates grew faster than under ambient conditions. Significant intraspecific variation was observed among G. clavigera isolates for all parameters tested. Key words: Grosmannia clavigera, Ophiostoma clavigerum, mountain pine beetle, blue-stain fungus, intraspecific variation, pathogenicity. Grosmannia clavigera est le plus pathogénique des champignons du bleuissement associés au dendroctone du pin ponderosa (Dendroctonus ponderosae). Contrairement à son importance en tant qu’envahisseur primaire de l’aubier du pin tordu latifolié (Pinus contorta), la variabilité intraspécifique de la pathogénicité de G. clavigera envers ce dernier, hôte principal du dendroctone du pin ponderosa en Colombie-Britannique, n’a pas été étudiée en détail. Les présents travaux font état d’indicateurs de pathogénicité produits par cinq isolats de G. clavigera appliqués sur des pins tordus latifoliés ainsi que des caractéristiques de croissance de ces isolats cultivés en milieu artificiel. De jeunes pins tordus latifoliés ont été inoculés avec le champignon à raison de 200 inoculations/m2. Au bout de 7 ou 48 semaines, la longueur des lésions subies par le phloème, la surface d’occlusion de l’aubier ainsi que son degré d’humidité ont été mesurés. Au bout de 48 semaines, comparativement aux deux autres, trois des cinq isolats avaient produit de longues lésions, occlus de plus larges surfaces et avaient davantage réduit le degré d’humidité. Au bout de 7 semaines, l’isolat ATCC 18086 avait provoqué les symptômes pathogènes les plus aigus. Son taux de croissance avait également été le plus rapide, et ce, jusqu’à 22,5 °C, pour devenir le plus lent à 27,5 °C. La plupart des isolats ont crû plus rapidement dans un environnement faible en oxygène que dans les conditions de milieu ambiant. Une variation intraspécifique significative a été observée chez les isolats de G. clavigera, et ce, relativement à tous les paramètres analysés. Mots-clés : Grosmannia clavigera, Ophiostoma clavigerum, dendroctone du pin ponderosa, champignon du bleuissement, variation intraspécifique, pathogénicité.

Temporal change in wood quality attributes in standing dead beetle-killed lodgepole pine

The number and size of checks, wood moisture content, extent of blue-stain, rot and decay was examined by stem analysis in 360 mature standing beetle-killed lodgepole pines. Trees came from three areas (Burns Lake, Quesnel, and Vanderhoof) in Central British Columbia. Each area was represented by 14 to 16 sampling areas (stands) distributed evenly across three soil moisture regimes (dry, mesic, wet). Year of death was estimated from tree ring-analysis, local knowledge and insect and disease survey maps. An approximately equal number of trees had been dead for one or two years, three or four years, or for five or more years. During the first five years since death by beetle attack the number of checks per tree increased from 2.5 to 10.2 and the average depth of checks increased from 4.3 cm to 5.1 cm. Checks were deeper, wider, and longer on the drier sites than on mesic and wet sites. Moisture content of sapwood and heartwood was near the fibre saturation point (ca 30%) one year after death and continued to decrease at a rate of approximately 1.7% per year. Both the incidence and the extent (relative to basal area) of rot and decay increased significantly with time since death. All trees had an extensive blue-stain discoloration. Deterioration of wood quality was fastest during the first two years after a beetle attack. Key words: wood checks, moisture content, blue-stain, wood quality, spiral grain, bark beetle

White Pine Blister Rust Severity and Selection of Individual Whitebark Pine by the Mountain Pine Beetle (Coleoptera: Curculionidae, Scolytinae)

We investigated whether white pine blister rust (Cronartium ribicola) (J.C. Fischer in Rabenh.) severity, tree diameter at breast height (DBH), bark and phloem thickness, and sapwood moisture content influence the preference of the mountain pine beetle (Dendroctonus ponderosae Hopkins) for individual trees of whitebark (Pinus albicaulis Engelm.) and lodgepole pine (P. contorta Loud.). We measured these variables at 5 sites in Montana and Idaho and found a significant relationship between blister rust severity and attack of trees by D. ponderosae, with trees exhibiting greater blister rust severity being more likely to be attacked by the beetle. Sapwood moisture content was negatively correlated (P = 0.0004) with blister rust severity indicating that as severity increases there is an increasingly negative effect on water relations within the tree. Sapwood moisture content was significantly lower in P. albicaulis than in P. contorta at sites with beetle activity suggesting that there may be an interaction between blister rust severity and drought stress that, in turn, may affect beetle preference. DBH and bark and phloem thickness did not appear to influence beetle preference for individual trees. As blister rust spreads in P. albicaulis stands across the western U.S., this may translate to increasing levels of beetle-caused mortality in these areas.

Moisture and blue stain distribution in mountain pine beetle infested lodgepole pine trees and industrial implications

Healthy lodgepole pine trees and trees at three stages (green, red and grey) of infestation by mountain pine beetles (MPB) were examined for moisture and blue-stain distribution in the radial and longitudinal directions. The sapwood moisture content of trees dropped about 100% from the healthy stage while the heartwood moisture dropped about 10%, regardless of green, red or grey attack stages. Moisture content variation with tree height was unique up to the time since beetle attack. The volume of blue stain increased with increasing time since beetle attack. Maximum discolouration in wood occurred at about 3 m above ground level and expanded rapidly upward. Lumber sawn and tracked from the MPB attacked logs showed a decrease in moisture content with increasing time since beetle attack, indicating the need for specific drying schedules employing lower energy levels. The economic implication of the effect of blue stain was evaluated by the percentage of Japanese grade (J-grade) lumber produced. The J-grade lumber yield decreased with increasing time since beetle attack. Early harvest and conversion of MPB infected trees will positively impact product value and recovery.

Wet Heartwood Distribution in the Stem, Stump, and Root Wood of Black Spruce in the Quebec Boreal Forest, Canada

Abstract Wet heartwood has been studied since the beginning of the 20th century. The present work focused on wet heartwood of 44 black spruces (Picea mariana (Mill.) B.S.P.) from boreal forest swampy sites Quebec, Canada. Trees were studied to characterize their tree crown shape, quickly identify them in the field, measure their moisture content, establish their moisture content distribution pattern, evaluate the wet heartwood volume inside their stem, and find the possibility of water entrance in this species. Black spruces with wet heartwood were characterized by a typical tree shape with a small number of living branches, short branches, and a clump of green needles at the top of the tree. The wet heartwood was characterized by high moisture content at the stem base and decreased with stem height. Wet heartwood was observed as high as 5 m above stem base for trees around 10.5 m in height. Moisture content of sapwood along the stem varied from 81 to 161%, whereas in dry heartwood, it was around 43% but reached more than 100% in the wet heartwood. Wet heartwood volume in the first 3.25 m of black spruce stems averaged 13% with variations between 2 and 35% per study site. Twelve stumps had wet heartwood moisture contents reaching 143% or higher. Moisture content of wet heartwood in root sections closest to the stump varied along a gradient: lower or absent at ground level and increasing with depth up to a maximum value before decreasing again. North. J. Appl. For. 22(1):12–18.

Impact of the foliar pathogen Swiss needle cast on wood quality of Douglas-fir

Many stands of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) near coastal areas of Oregon and Washington are heavily infected with the foliar pathogen causing Swiss needle cast (SNC) disease, and yet there is very little research on the resulting wood quality. Modulus of elasticity (MOE), modulus of rupture (MOR), microfibril angle (MFA), wood density, latewood proportion, and sapwood moisture content were examined in 20- to 28-year-old trees from 15 stands that were infected with varying intensities of SNC. SNC severity was quantified by measuring needle retention, the number of needle cohorts retained at three crown levels. Correlations between disease severity and wood properties were examined at both the stand and within-stand levels. Trees from heavily infected stands (needle retention &lt;2 years) had higher MOE, wood density, and latewood proportion and lower sapwood moisture content than trees from healthier stands. Breast-height age (BHage) was also correlated with these properties, but age alone did not explain all of the increases. MFA was not associated with SNC severity. Within stands, needle retention was not associated with MOE or MOR. The increase in latewood proportion in diseased stands appears to be the driving factor behind their increase in stiffness (MOE). Ring width decreased with decreased needle retention, and the examined wood properties generally showed stronger correlations with ring width than with needle retention.

Ophiostomatoid and basidiomycetous fungi associated with green, red, and grey lodgepole pines after mountain pine beetle (Dendroctonus ponderosae) infestation

The mountain pine beetle (MPB) is a major concern for lodgepole pine (Pinus contorta var. latifolia Engelm.) forests in British Columbia, Canada. MPB and the ophiostomatoid staining fungi for which they serve as vector have a close, mutualistic relationship. In this work, we determined which fungi colonized MPB-killed standing trees with green, red, and grey crowns and quantified how rapidly the fungi stained and reduced the moisture content of sapwood. Green trees were mainly colonized by Ophiostoma clavigerum (Robinson-Jeffrey &amp; Davidson) Harrington, Ophiostoma montium (Rumbold) von Arx, Ophiostoma nigrocarpum (Davidson) De Hoog, Ophiostoma minutum (Olchow. &amp; Reid) Hausner, and unknown Leptographium species. In red and grey pines (2 and 3 years after the original MPB attack, respectively), the frequency of the original fungal colonizers decreased, and other sapstaining fungal species were encountered. Among basidiomycetous fungi, decay fungi were rarely present in green trees but were isolated more frequently in red and grey trees. The frequency and the type of decay fungi isolated varied between harvesting sites.

Influence of Bravo fungicide applications on wood density and moisture content of Swiss needle cast affected Douglas-fir trees

Wood density, moisture content, tracheid width and cell wall size were examined in trees from plots that were sprayed for 5 years with chlorothalonil (Bravo ®) fungicide to reduce the impact of Swiss needle cast (SNC) and from trees in adjacent unsprayed plots. The unsprayed (more heavily diseased) trees had significantly narrower sapwood, narrower growth rings, lower sapwood moisture content, and narrower tracheid cell wall thickness than did the sprayed (less heavily diseased) trees. Moreover, unsprayed trees had altered earlywood density—earlywood width relationships, higher latewood proportion, and higher overall wood density than the sprayed trees. We hypothesize: (1) that the decreased moisture content of diseased trees results from their poor carbon economy resulting in insufficient energy (photosynthate) to reverse sapwood embolisms, and (2) SNC decreases wood density relative to growth rate.

Drying of sapwood, heartwood and mixed sapwood and heartwood boards of Pinus radiata

boards in stacks of all sapwood, all heartwood and mixed sapwood and heartwood, using a tunnel dryer. Drying temperatures were 90/60 °C and airflow was reversed every three hours, with an average air velocity of 5.0 m/s. For stacks of all sapwood and all heartwood boards, the influence of board thickness and position of thicker and thinner boards in the stack was also examined. Boards with thicknesses of 37 and 45 mm were placed within a stack of 40 mm boards, and individual drying curves during drying were compared. Due to the higher initial moisture content of sapwood, the drying time for the all sapwood stack was almost twice as long as that for the all heartwood stack. In the mixed stack, the initial drying rate for sapwood was faster and that for heartwood slower than in segregated stacks, so that the difference in the drying time between sapwood and heartwood was less. To dry to an overall average moisture content of 10%, the all heartwood stack needed 20 hours, the sapwood stack 35 hours and the mixed sapwood/heartwood stack (55% sapwood) 30 hours. The drying rate for individual boards in the sapwood and heartwood stacks was related to thickness, but the differences were negligible once the overall moisture content fell below 10%.

Effects of clear-cutting, thinning, and wood moisture content on the susceptibility of Norway spruce stumps to Heterobasidion annosum

The effects of clear-cutting and thinning as well as heartwood and sapwood moisture content on spore infection by Heterobasidion annosum (Fr.) Bref. were investigated in summer cuttings in southern and central Sweden. At five sites, 20-100 stumps in clear-cut, thinned, and precommercially thinned stands of Norway spruce (Picea abies (L.) Karst.) were created and left for natural spore infection. An additional 20 stumps per stump type and site were artificially inoculated with conidiospores of H. annosum. The probability of natural infection was 0.73 and 0.53 for stumps in thinned and clear-cut stands, respectively. Almost all (95%) of the artificially inoculated stumps in thinned and clear-cut stands became colonized, and no differences due to stump type were found. The probability of infection of stumps in precommercially thinned stands was lower than for the other stump types of both naturally and artificially inoculated stumps. The proportion of colonized sapwood was reduced with increasing moisture content. Stump colonization seemed unaffected by temperature, even though stump temperatures exceeded 40°C for 2 h at one site.

Wood moisture content variation in white spruce defoliated by spruce budworm

Mature and over mature white spruce [Picea glauca (Moench) Voss] repeatedly defoliated by spruce budworm (Choristoneura fumiferana Clem.) in eastern Manitoba, were investigated for variation in moisture content (MC) which is known to influence pulping quality. In the fall of 1991, 100 trees in the Abitibi-Price Inc. Forest Management Licence area were selected randomly in two size classes and four defoliation classes. Heartwood and sapwood MC (% dry weight) was measured in 5-cm thick disks cut at 2.5 to 5.0 m intervals for small and large trees, respectively. Living trees with more sapwood than heartwood had a mean MC of 117%, and those with more heartwood than sapwood had a mean MC of 77%. Both of these groups contained sufficient overall moisture (&gt; 45%) for pulping. The repeated defoliation did not affect the overall MC in live trees. Mean MC of trees killed by spruce budworm defoliation was 42% but this level varied with diameter and height above ground: &gt; 45% in stems greater than 36 cm diameter inside bark, 30–60% in sections 17–36 cm, and &lt; 45% in sections less than 17 cm. A minimum DBH of 30 cm is suggested as a criterion for accepting dead trees. Key words: insect defoliation impact, wood moisture content, sapwood, heartwood, dead tree fibre, Manitoba

A comparison of sampling methods for determining the sapwood moisture content of Norway Spruce

Aus aktuellem Anlas werden einige methodische Schwierigkeiten bei der Bestimmung der Feuchte von Stammholz beschrieben. Eine vergleichende Untersuchung von mit verschiedenen Entnahmewerkzeugen gewonnenen Proben aus im Fruhjahr 1990 angefallenen Fichten-Windbruch-Stumpfen zeigt, das die gravimetrisch ermittelte Feuchte der Probekorper in Abhangigkeit vom jeweiligen Entnahmeverfahren ganz erheblich variiert. Die Vorteile einer verfeinerten Methode zur Bestimmung des Wasserzustandes im Holz werden gegenuber der ublicherweise verwendeten darrgewichtsbezogenen Holzfeuchte erlautert.