Proportion Of Bark Research Articles

Assessment of suitability of tree species for the production of biomass on trace element contaminated soils

To alleviate the demand on fertile agricultural land for production of bioenergy, we investigated the possibility of producing biomass for bioenergy on trace element (TE) contaminated land. Soil samples and plant tissues (leaves, wood and bark) of adult willow (Salix sp.), poplar (Populus sp.), and birch (Betula pendula) trees were collected from five contaminated sites in France and Germany and analysed for Zn, Cd, Pb, Cu, Ca, and K. Cadmium concentration in tree leaves were correlated with tree species, whereas Zn concentration in leaves was site correlated. Birch revealed significantly lower leaf Cd concentrations (1.2–8.9mgkg−1) than willow and poplar (5–80mgkg−1), thus posing the lowest risk for TE contamination of surrounding areas. Birch displayed the lowest bark concentrations for Ca (2300–6200mgkg−1) and K (320–1250mgkg−1), indicating that it would be the most suitable tree species for fuel production, as high concentrations of K and Ca decrease the ash melting point which results in a reduced plant lifetime. Due to higher TE concentrations in bark compared to wood a small bark proportion in relation to the trunk is desirable. In general the bark proportion was reduced with the tree age. In summary, birch was amongst the investigated species the most suitable for biomass production on TE contaminated land.

Peso medio de las bellotas de Quercus robur L. en Galicia. Influencia de factores fisiográficos y dasométricos.

The starting point of this work has been the accomplishment of a forest inventory in stands of the most abundant autochthonous species of the kind Quercus in the Peninsular Northwest (Quercus robur L., Q. pyrenaica Willd. and Q. petraea (Matts.) Liebl.). With the obtained information, have been calculated the ecological and silvicultural parameters needed to characterize ecologically the forest station and also describe, from the stand point of forestry, such stands so that it is possible to know the potential of the different locations for obtaining of suitable wood for aging wine, allowing even know in advance whether or not perform silvicultural activities to achieve that objective. On the other hand, the information xilology (wood physical parameters, such as the proportion of bark, sapwood and heartwood, density, porosity and grain of the wood) obtained from different samples from trees felled in the stands inventoried, will allow us to value the suitability of the wood for the production of barrels of species studied.

Assessment of biomass functions for calculating bark proportions and ash contents of refined biomass fuels derived from major boreal tree species

Knowledge of the components of above-ground biomass of low-quality stems harvested to produce biofuel pellets is important, since bark has higher ash contents (a key quality parameter for the pellets) than wood. Therefore, single-tree biomass functions by Marklund (1988. Rep. 45. Department of Forest Survey, Swedish University of Agricultural Sciences, Umea, Sweden.) were evaluated using a sample population of 1612 Scots pine ( Pinus sylvestris L.), Norway spruce ( Pices abies (L.) Karst.), and birch ( Betula pendula Roth and Betula pubescens Ehrh.) trees and three methods to model bark proportions. Bark percentages calculated subtractively using functions for stem biomass over and under bark showed anomalous patterns, especially for pine and birch. However, additive use of biomass functions for bark biomass and stem biomass under bark resulted in similar patterns to bark percentages traditionally calculated from bark biomass and stem biomass over bark. Published ash contents of bark and stemwood indicate that pine, birch, and spruce stems with breast height (1.3 m) diameters of 4–40, 4–30, and >19 cm, respectively, have <0.7% ash contents (the current limit for the highest quality fuel pellets). However, if the highest recorded ash contents are used, only pine stems meet this criterion. Thus, material of different species and stem dimensions may need to be carefully mixed when whole-stem biomass is used as feedstock for pelletizing.

Characterization of NAC domain transcription factors implicated in control of vascular cell differentiation in Arabidopsis and Populus

Wood has a wide variety of uses and is arguably the most important renewable raw material. The composition of xylem cell types in wood determines the utility of different types of wood for distinct commercial applications. Using expression profiling and phylogenetic analysis, we identified many xylem-associated regulatory genes that may control the differentiation of cells involved in wood formation in Arabidopsis and poplar. Prominent among these are NAC domain transcription factors (NACs). We studied NACs with putative involvement as negative (XND1 from Arabidopsis and its poplar orthologs PopNAC118, PopNAC122, PopNAC128, PopNAC129), or positive (SND2 and SND3 from Arabidopsis and their poplar orthologs PopNAC105, PopNAC154, PopNAC156, PopNAC157) regulators of secondary cell wall synthesis. Using quantitative PCR and in situ hybridization, we evaluated expression of these Populus NACs in a developmental gradient and in association with reaction wood and found that representatives from both groups were associated with wood-forming tissue and phloem fibers. Additionally, XND1 orthologs were expressed in mesophyll cells of developing leaves. We prepared transgenic Arabidopsis and poplar plants for overexpression of selected NACs. XND1 overexpression in poplar resulted in severe stunting. Additionally, poplar XND1 overexpressors lacked phloem fibers and showed reductions in cell size and number, vessel number, and frequency of rays in the xylem. Overexpression of PopNAC122, an XND1 ortholog, yielded an analogous phenotype in Arabidopsis. Overexpression of PopNAC154 in poplar reduced height growth and increased the relative proportion of bark versus xylem.

Anatomical studies of stems, roots and leaves of selected citrus rootstock varieties in relation to their vigour

The present studies were carried out to consolidate information on anatomical features of stem, root and leaves from different vigour groups of citrus rootstock varieties. Troyer citrange (Citrus sinensis × Poncirus trifoliata), rough lemon (Citrus jambhiri), swingle citrumelo (Citrus paradisi × P. trifoliata), sweet lime (Citrus limettioides), carrizo citrange (C. sinensis × Poncirus trifoliata), sour orange (Citrus aurantium) and flying dragon (P. trifoliata) were examined to investigate relationships between their internal structure and vigour. It was found that vigorous rootstock, rough lemon (C. jambhiri) possessed lower proportions of bark (phloem) in the stems and roots as well as larger vessel elements in the xylem, when compared with least vigorous rootstocks, flying dragon (P. trifoliata). Smaller but more vessel elements were found in stem cross-sections than root cross-sections of three month’s old rootstock seedlings. The possible mechanism of vascular differentiation induced by young leaf primordia, following the original polarity and developing toward the roots is discussed. Key words: Citrus rootstock, anatomical features, stem, root, leaves.

The chemical composition of medieval wood ash glass from Central Europe

Medieval wood ash glass classified as 6 early medieval wood ash glasses, 17 wood ash glasses, 5 early wood ash lime glasses, 7 wood ash lime glasses and 9 mixed alkali glasses has been analyzed by microprobe and ICP-mass spectrometry on 61 elements. Their calcium oxide to potassium oxide ratio (CaO/K 2O) increases from early to late medieval glasses according to an increase of the proportion of twigs in the bulk amount of wood (logs plus twigs). Twigs because of their relatively large proportion of bark contain more calcium than wood logs. The ratio CaO/K 2O of the glasses from not yet evaluated excavations can be used for dating. The observation that the 25 minor elements Be, Sc, V, Cr, Ge, Y, Nb, REE (La to Lu), Ta, W and Bi occur in almost equal concentrations in the five subtypes of wood ash glass makes it highly probable that these elements were introduced into the starting mixtures of the glasses by means of quartz from quartz-rich sand with heavy minerals. The majorities of the wood ash glasses contain so-called europium anomalies within the group of rare-earth elements (REE). Their Eu concentrations normalized to those of the Continental Earth's Crust are lower than the normalized samarium and gadolinium concentrations. These Eu anomalies are apparently inherited from the granitic source of quartz in the upper Continental Earth's Crust. Soda ash and soda lime glass as the other major types in the history of glass contain no Eu anomaly. Therefore a different source of quartz has caused this important element constellation for these glass types. The elements K, Cu, Rb and S are physiologically separated from Ca, P, Mn, Sr and B during the growth of the wood and bark, respectively, in the trees. Different sources of the metals Cu and Co were used for colouring the glasses of our report.

Analysis of Biomass Composition Using High-Resolution Thermogravimetric Analysis and Percent Bark Content for the Selection of Shrub Willow Bioenergy Crop Varieties

Rapid determination of biomass composition is critical for the selection of shrub willow varieties with optimized biomass properties for conversion into fuels or chemicals. In order to improve the process for identifying and selecting shrub willow clones with distinct biomass composition, high-resolution thermogravimetric analysis (HR-TGA) was developed as a rapid, low-cost method for analyzing large numbers of willow biomass samples. In order to validate the HR-TGA method, bulk biomass collected from 2-year-old stems of a selected set of 25 shrub willow clones was analyzed using traditional wet chemistry techniques in addition to HR-TGA. The results of the wet chemistry and the HR-TGA method were compared using regression analysis resulting in R-squared values above 0.7 for the three main wood components, cellulose, hemicellulose, and lignin. Bark was removed from duplicate stem samples of the same clones, the proportion of bark was determined, and the debarked wood was used for HR-TGA analysis of composition. While there were significant differences in the proportions of lignin and cellulose in debarked wood compared to bulk biomass, as well as significant differences in bark percentage among clones, there was no correlation between bark percentage and bulk biomass component analysis. This work validates the effectiveness, precision, and accuracy of HR-TGA as a reasonably high-throughput method for biomass composition analysis and selection of shrub willow bioenergy crop varieties.

Wood fuel quality of two Salix viminalis stands fertilised with sludge, ash and sludge–ash mixtures

Abstract This study assessed the effects of stand structure and fertilisation with wood ash and/or sludge on wood fuel quality of Salix viminalis. The relative proportions of bark and wood in 1-, 2- and 3-year-old shoot populations were determined. The concentrations of essential elements (N, P, K) and heavy metals (Cu, Zn, Cd, Ni) in bark and wood were used to assess the wood fuel quality in harvestable shoot biomass. Controlled field experiments were conducted on two newly harvested commercial short-rotation willow coppice fields. Five treatments were applied: sewage sludge at the maximum legally permitted amount; ash; two sludge–ash mixtures supplying the maximum and twice the maximum permitted sludge–ash amount; and a control receiving mineral nutrients only. The proportion of bark in the willow stands was decreasing with the age of the shoot population. The shoot population with few large stems, compared to that with many small stems, had a lower proportion of element-rich bark in the harvestable shoot biomass, meaning better quality of the wood fuel. Overall, wood fuel quality in terms of mineral concentrations was influenced by the age of the shoot population at harvest, stand structure, management practices (e.g. planting density, fertilisation) and site conditions (soil type, element availability). Our results imply that harvestable shoot biomass of willows grown as few large stems have better wood fuel quality, compared to harvestable shoot biomass of many small stems. Increased length of cutting cycle improves the wood fuel quality.

Biomass and element pools of selected spruce trees in the catchments of Plešné and Čertovo Lakes in the Šumava Mts.

This paper presents detailed data on the biomass and element pools of six sample trees in the catchments of Plešné andČertovoLakes. Diameters and heights of the sample trees ranged from 28.0 to 63.7 cm and from 14.1 to 38.7 m. The age of the sample trees ranged from 84 to 177 years. Total biomass of the sample trees was in the range of 239.4 kg to 2,932.3 kg. Variation of total biomass between the sample trees was a consequence of the tree biometric data (height and dbh) and age differences. The proportion of stem wood and bark ranged from 63.5 to 69.5%, and from 4.6 to 7.2%, respectively. The proportion of foliage and fine branches ranged from 4.3 to 8.4%, and from 0.7 to 1.9%, respectively. The proportion of branch wood and bark ranged from 2.2 to 6.5%, and from 0.8 to 2.2%, respectively. Mean concentrations of C in different tree components were quite similar. Except C and compared to the other elements, N had the highest mean concentrations in tree components in all cases. Concentrations of P, Ca, Mg, and K showed similar patterns. Generally the highest concentrations of these elements were found in foliage, fine branches, fine roots and bark of stem and branches. Fe, Na, Al and Mn showed the lowest mean concentrations in tree components for all the analyzed elements. The total element pools per tree were highly variable because of the differences in total biomass between the individual trees. Generally, stem wood and bark, foliage, and roots contained the highest proportion of the elements. But there were differences between individual elements. Concerning the important nutrients, while the highest proportion of Ca and Mg was contained in stem wood and bark, the highest proportion of P was contained in foliage. The foliage contained a relatively high proportion of P and K, but a relatively low proportion of Ca and Mg.

EFFECT OF THE CONCENTRATION OF CHIPPED BARK IN SAWDUST SUBSTRATE ON CRUDE POLYSACCHARIDE EXTRACT AND LENTINAN CONTENT OF SHIITAKE MUSHROOMS

Shiitake mushrooms contain lentinan, a polysaccharide that has numerous medicinal benefits. The objective of this research was to determine the impact of various rates of chipped and sawmill bark added to the substrate on lentinan found in shiitake mushrooms. Crude polysaccharide extract (CPE) and lentinan (LTN) content was significantly different among shiitake mushrooms grown on various artificial substrates containing different percentages of sawdust and chipped bark. The addition of chipped bark content from 0% to 50% increased the CPE content, but an increase in chipped bark content from 50% to 100% decreased the CPE and LTN content. CPE content in mushrooms was greater when equal proportions of sawdust and bark were used. A 100% heartwood treatment had the least CPE content.

Total above-ground biomass and biomass in commercial logs following the harvest of spotted gum (Corymbia maculata) forests of SE NSW

Summary Total stand above-ground biomass (AGB) was measured at three sites of varying productivity in the Batemans Bay region of NSW. All trees with diameter at breast height (dbh) > 10 cm on three plots of 0.4–0.6 ha were weighed. Spotted gum was the dominant tree species across all sites. The basal area ranged from 29 to 43 m ha−1 depending on site quality. The total dry AGB was 220, 287 and 397 t ha−1 for the low, medium and high-quality sites (LQS, MQS and HQS), respectively. Spotted gum accounted for 66–79% of the AGB. The proportion of AGB in larger trees (dbh >50 cm) increased significantly with increased site quality. Bark accounted for about 7% of the weight of all spotted gum logs. The only significant differences in the proportion of bark in the logs were between trees with dbh >70 cm and those with dbh <40 cm. Ironbark had the highest proportion of the log biomass in the bark (12.4%). The mean moisture content of spotted gum logs was similar to that of Sydney blue gum and yellow stringybark logs. The moisture content of ironbark logs was significantly lower than that of all other species tested, whereas its basic density was higher than that of all other species. A strong correlation (r = 0.947) was found between tree diameter and AGB for spotted gum across all sites. Most trees on all sites were < 30 cm in diameter (particularly at the low-quality site), and the variance of AGB increased with tree size. The fraction of biomass in all spotted gum commercial logs was 58.2%. The biomass in commercial logs at the MQS was significantly greater than that at both the LQS and the HQS. An average 0.8 t of residues was generated per tree as a result of selective harvesting of commercial spotted gum forests. The largest fraction of biomass in commercial spotted gum logs (64.1%) was found in large trees (55–65 cm dbh), although the only significant differences were between trees with dbh between 35 and 40 cm and those with dbh between 55 and 65 cm. Pulp logs accounted for 55% of the AGB harvested in spotted gum commercial logs. The proportion of higher-quality commercial logs increased with increased site quality.

Estimation and relevance of bark proportion in a willow stand

Abstract We studied bark proportion of a willow ( Salix viminalis ) plantation established to produce biomass for energy, the vertical distribution of elements (N, P, K, Mg, Ca, Co, Cu, Zn, As, Si, Cd, Cr, Pb, Hg and Ni) in bark and in wood of the shoots and the content of elements in the standing biomass. The study is based on 5-year-old shoots (clone 77-683) from a 12-year-old plantation. The bark proportion of the whole willow stand was 19% ( 9 tDM ha - 1 ) . The bark proportion of single shoots was constant after they had reached the size of 20 mm at stem diameter at 55 cm height. Compared to wood, bark had significantly higher concentrations of N, P, K, Mg, Ca, Cd, Pb, Co and Zn. The nutrient element (N, P, K, Mg) concentrations in the bark and in the wood of the current year shoot fractions (twigs) were significantly higher compared to the bark and the wood of other fractions. The accumulation of heavy metals occurred due to the accumulation of tree biomass and not due to the increase of heavy metal (Cd, Cr, Pb and Hg) concentrations in plant tissues over time. In summary, different management regimes give a possibility to influence shoot size frequency distribution of the crop and the chemical composition of biomass. For minimizing element removals from the soil and corrosion processes in power plants, energy willow stands should be managed in a way that promotes low bark proportion and thereby as little nutrient removal from the site by biomass harvest as possible.

Dry season diets and habitat use of sympatric Asian elephants (Elephas maximus) and greater one‐horned rhinoceros (Rhinocerus unicornis) in Nepal

Dry season diets and habitat use of increasing populations of Asian elephants Elephas maximus and greater one-horned rhinoceros Rhinoceros unicornis in the Babai Valley of Royal Bardia National Park, Nepal, are described, and an assessment is made of the potential for competition between them. The diets, analysed by microhistology, were different, with a similarity index of 37.5%, and with different grass/browse proportions: the rhino diet consisted of 63% grass and 28% browse; that of elephants was 24% grass and 65% browse. A tallgrass floodplain grass, Saccharum spontaneum, was the plant most eaten by rhinos, whereas elephants consumed a large proportion of bark of Bombax ceiba and Acacia catechu, as well as several browse species not eaten by rhino. The habitat use of elephants was determined by dung-counts within 30 km of 20-m wide belt transects, while that of rhino was taken from an earlier study. Elephants used a wider range of habitats than rhino, but two types, the tallgrass floodplain and khair–sissoo forest, were preferred by both species simultaneously. While elephants used the abundant sal forest extensively, rhino strongly avoided this habitat. Densities of both species were low at the time of study (<0.5 animals/km2), but their numbers are expected to increase markedly in coming years. Because available habitats for expansion are limited, this may lead to competition. Rhino might then become the weaker species, as elephants are more flexible in their ranging and foraging activities. The tallgrass floodplain habitat and its important forage grass S. spontaneum may then become the critical resources.

Bark anatomy of Nothofagus species (Nothofagaceae) indigenous to the Andean - Patagonian forest, Argentina

The bark structure of Nothofagus alpina (Poepp. et Endl.) Oerst., N. antarctica (G.Forster) Oerst. N. obliqua (Mirbel) Oerst., N. pumilio (Poepp. et Endl.) Krasser, N. betuloides (Mirbel) Oerst. and N. dombeyi (Mirbel) Oerst, native species from the Andean–Patagonian forests (Argentina), is described. Barks of the Nothofagus species are greyish to dark brown and have deep fissures, except that of N. obliqua. Non-collapsed secondary phloem has abundant sieve elements with scalariform compound sieve plates in oblique end walls, and with rounded to polygonal sieve areas in tangential walls. Axial parenchyma in secondary phloem is diffuse and/or arranged in discontinuous uni–triseriate tangential lines and bands. Crystalliferous axial parenchyma is present adjacent to sclerenchyma. Rays are usually homocellular, exclusively uniseriate in N. dombeyi to bi–triseriate in the other species. Fibres in secondary phloem are arranged in clusters, tangential lines and bands. Combined fibre and sclereid clusters are present in N. betuloides. Persistent rhytidomes usually include a variable proportion of bark. The present study helps to confirm the taxonomic placement of Nothofagaceae as a distinct family from Fagaceae, and supports the infrageneric classification of Nothofagus proposed by different authors.

Chemical and carbon-13 cross-polarization magic-angle spinning nuclear magnetic resonance characterization of logyard fines from British Columbia.

Phasing out beehive burners and rising costs for landfilling have increased the need to widen options for utilization of the smaller size fractions of woody wastes generated during log handling and sawmilling in British Columbia. We characterized several size classes of logyard fines up to 16 mm sampled from coastal and interior operations. Total C, total N, ash, and condensed tannin concentrations were consistent with properties derived largely from wood, with varying proportions of bark and mixing with mineral soil. Especially for < 3-mm fractions, the latter resulted in high ash contents that would make them unsuitable for fuel. Solid-state 13C cross-polarization magic-angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectra were consistent with the chemical data, with high O-alkyl intensity and similarity to naturally occurring woody forest floor; no samples were high in aromatic or phenolic C. Aqueous extracts of two < 16-mm fines, which accounted for only a small proportion of the total C, were enriched in alkyl C and had low or undetectable tannins. Application to forest sites might cause short-term immobilization of N, but also might include possible longer-term benefits from reduction of N loss after harvesting and restoration of soil organic matter in degraded sites.

Bark heat resistance of small trees in Californian mixed conifer forests: testing some model assumptions

An essential component to models of fire-caused tree mortality is an assessment of cambial damage. Cambial heat resistance has been traditionally measured in large overstory trees with thick bark, although small trees have thinner bark and thus are more sensitive to fire. We undertook this study to determine if current models of bark heat transfer are applicable to small trees (<20 cm diameter at breast height (dbh)). We performed this work in situ on four common species in the mixed conifer forests of the Sierra Nevada, California. The allometric relationship between bole diameter and bark thickness for each species was linear, even for very small trees (5 cm dbh). Heating experiments demonstrated that bark thickness was the primary determinant of cambial heat resistance. We found only slight, but statistically significant, among species differences in bark thermal properties. Our most significant finding was that small trees were more resistant to heating than expected from commonly used models of bark heat transfer. Our results may differ from those of existing models because we found smaller trees to have a greater proportion of inner bark, which appears to have superior insulating properties compared to outer bark. From a management perspective, growth projections suggest that a 50-year fire-free interval may allow some fire intolerant species to achieve at least some degree of cambial heat resistance in the Sierra Nevada.

Suitability of kiwi ( Actinidia sinensis Planch.) prunings for particleboard manufacturing

The aim of this study was to investigate the suitability of kiwi prunings as a raw material for particleboard manufacturing. The kiwi is a new cultivation in the East Black Sea Region of Turkey. Kiwi pruning particles and industrial wood particles in various proportions were used as the raw material for the core and surface layers of the three-layer particleboard. Commercial urea formaldehyde (UF) adhesive was used as a binder. Anatomical descriptions, chemical properties (holocellulose, cellulose, lignin and ash contents, alcohol–benzene, hot and cold water solubility, solubility in dilute alkali (1% NaOH)) and basic characteristics of the kiwi stalks (density, weight proportion of bark, core and pith), physical (thickness swelling (TS), water absorption (WA)), and mechanical (modulus of rupture (MOR), modulus of elasticity (MOE), internal bond (IB)) properties of particleboards were determined. The results showed that kiwi stalks had higher fiber length, width and wall thickness values than the wood of common forest species. They had higher solubility values, lignin and ash contents than those of the other plants. Increasing of kiwi pruning particles usage in the core negatively affects the board properties. Containing up to 50% kiwi pruning particles in the core, the MOR exceed the minimum requirements of the European standards, for general purpose. All of the particleboards produced from kiwi prunings had IB higher than the requirement. The WA and TS values were very high (poor).

Wood and bark of some poplar and willow clones as fuelwood

Poplars and willows are widely used to produce biomass for energy. Calorific values of wood and bark, as well as for whole tree of Populus × euramericana (cl. I-214), Populus deltoides (cl.PE 19/66) and white willow Salix alba (cl.378) of different ages were determined. one- and 2-year-old rooted cuttings were grown in plantations with high planting density, in order to produce a high biomass yield per hectare. Mature trees in both species (poplar and willow) originated from the corresponding plantations; willow 14-year old, and poplar 12 years (cl.I-214) and 8 years (cl.PE 19/66). As the share of bark depends on the age of wood, calorific values were determined separately for bark and for wood. The share of bark (proportion of total weight) in 1- and 2-year-old rooted cuttings ranged between 18% and 27%, and in older trees it was from 10% to 15%. The higher heating values of oven dry poplar wood (calculated for the whole tree, based on the proportion of bark) were from 15,787 (cl. I-214 1-year old) to 24,275 kJ/kg (cl.I-214 2-year old). The average calorific values of willow wood (whole tree with bark) were from 16,169 (14-year old) to 22,572 kJ/kg (2-year old). It should be pointed out that the calorific value of wood is more favorable than that of bark, and the highest calorific values refer to 2-year-old trees.

Allometry and biomass of Korean pine ( Pinus koraiensis) in central Korea

Aboveground tree biomass of Korean pine ( Pinus koraiensis Sieb. et Zucc.) was determined for a natural forest of Korean pine and mixed deciduous trees and seven age classes of plantation forests in central Korea. Regression analyses of the dry weights of stem wood, stem bark, branches, and needles versus diameter at breast height were used to calculate regression equations of the form of log Y=a+b log X . Biomass of Korean pine in the mixed forest was 118 Mg ha −1, and biomass in the plantations was linearly related to stand age, ranging from 52.3 Mg ha −1 in 11 to 20-year-old stands to 317.9 Mg ha −1 in 71 to 80-year-old stands. The proportions of stem wood and stem bark in the total aboveground biomass decreased with stand age while those of branch and needle increased. Specific leaf area of Korean pine ranging from 35.2 to 52.1 cm 2 g −1 was significantly different among crown positions and needle ages; in general, lower crown position and current needles had the greatest surface area per unit dry weight.

Decomposition and nitrogen release from decomposing woody roots in coniferous forests of the Pacific Northwest: a chronosequence approach

Decomposition of woody roots in Sitka spruce (Picea sitchensis (Bong.) Carrière), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), and ponderosa pine (Pinus ponderosa P. Laws. ex C. Laws.) dominated forests in Oregon, U.S.A. was studied using a chronosequence. Roots of five coniferous species were excavated from stumps with ages up to 46 years old. In order of increasing decomposition rate constant (k) the species were Douglas-fir &lt; Sitka spruce &lt; lodgepole pine (Pinus contorta Dougl. ex Loud.) &lt; western hemlock (Tsuga heterophylla (Raf.) Sarg) &lt; ponderosa pine. Variation in the proportion of bark, wood, and resin cores was correlated to these differences. Root wood showed the highest k, root bark the second, and resin cores the lowest. The occurrence of resin cores in woody roots of Douglas-fir, Sitka spruce, and lodgepole pine greatly slowed the decomposition of these species. White rots occurred frequently in ponderosa pine and lodgepole pine, whereas brown rots mostly appeared in Douglas-fir and Sitka spruce. Species with white rot had a higher k than those with brown rot. Decomposing woody roots started to release N after 20–30% mass loss, a point when the dead root C/N ratio averaged 140.