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1.
Die bisher erarbeiteten Ergebnisse lassen sich wie folgt zusammenfassen:
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Bei der Fichte korrelieren Jahrringbreite und Holzdichte und damit die wesentlichen Festigkeitseigenschaften, wie Biegefestigkeit,
Biege-E-Modul, Druckfestigkeit.
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Die Holzdichte als wesentliche Eigenschaft steht in enger Beziehung zum Sp?tholzanteil.
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Die Astst?rke korreliert direkt mit der Wachstumsgeschwindigkeit, d. h. ebenfalls mit der Jahrringbreite.
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Astst?rkensumme und Jahrringbreite zusammen erkl?ren einen gro?en Teil der technischen Holzeigenschaften.
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Durch Wert?stung kann ein Teil der negativen Wirkungen des schnellen Wachstums auf die Festigkeitseigenschaften ausgeglichen
werden.
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Dies bedeutet allerdings nicht, da? die Holzdichte als wesentliches Merkmal an Bedeutung verliert.
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Eine weitgehend zu erwartende Reihung ist also aus holztechnologischer Sicht eindeutig festzustellen:
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— engringig und wertge?stet auf dem 1. Platz, verspricht also h?chsten Holzwert,
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— engringig, nicht wertge?stetes Holz steht an 2. Stelle,
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— weitringig, wertge?stet im Mittelfeld, nur knapp nach Position 2
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— weitringiges, nicht wertge?stetes Holz verliert, mit Abstand an letzter Stelle stehend.
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Results achieved till now may be summarized as follows:
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With spruce, annual ring width is correlated with wood density, and thus with the essential strength properties such as bending
strength, bending-E-module, and tensile strength.
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Wood density as an essential property is closely related to the share of late wood.
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There is a direct correlation between knot size and growth rate, i. e. also annual ring width.
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The sum of knot diameters and annual ring width together explain a large part of the technical wood properties.
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High pruning may compensate for some of the negative effects of rapid growth on strength properties.
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This, however, does not imply that wood density is becoming less important as an essential property.
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From the wood-technological viewpoint, a largely to be expected ranking can be clearly established:
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— narrow growth rings and high-pruned stands in first place, thus promising the highest timber value,
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— narrow growth rings but not pruned comes second,
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— wide growth rings and high-pruned ranks about in the middle, only slightly behind position 2,
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— wood showing wide growth rings and not being from pruned trees falls way behind.
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相似文献
2.
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• Radiata pine (Pinus radiata D. Don) is the main exotic plantation tree species grown in New Zealand for wood production and as such represents a significant
component of the terrestrial carbon cycle. 相似文献
3.
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• We studied the differences in branch characteristics along the stems of six different genetic entries of 20 year old Scots
pines (Pinus sylvestris L.) grown at different spacing (current stand density range 2000–4000 trees ha−1) in central Finland. Furthermore, we studied the phenotypic correlations between yield, wood density traits and branch characteristics.
All the genetic entries had Kanerva pine (plus tree S1101) as a father tree, whereas the mother tree represented Finnish plus
trees from southern, central and northern Finland. 相似文献
4.
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• The vibration damping coefficient (tanδ) of wood is an important property for acoustical uses, including musical instruments.
Current difficulties in the availability of some of the preferred species call for diversification, but this comes up against
the lack of systematic damping coefficient data. 相似文献
5.
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• Vène wood (Pterocarpus erinaceus Poir.) is currently the favorite wood for manufacture of xylophone in Mali. A dynamic analysis method with free boundary
conditions, known as BING, was used to determine the main acoustic properties: specific dynamic modulus (E
L
/ρ), damping coefficient or internal friction (tan δ), sound radiation coefficient (SRC) and peak response (PR). 相似文献
6.
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• Fungal attack in wood involves severe mechanical losses, even in the early stages, due to depolymerisation of polysaccharides.
The safety of building components could therefore be affected. It is believed that fracture properties could be much more
sensitive to decay than conventionally measured properties, such as weight loss. 相似文献
7.
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• Coarse woody debris (CWD) plays a substantial role in several ecological processes in forest ecosystems, providing a habitat
for many organisms and participating in biogeochemical fluxes. Understanding CWD dynamics is important to classify adequate
density, size and amount into different decay classes and to make decisions that include biodiversity and the carbon budget
in practical forestry. 相似文献
8.
With large areas of public native forests now converted into National Parks and unavailable for timber harvest, private native
forests (PNF) in New South Wales (NSW) are becoming increasingly important in providing timber for the wood processing industry.
At the same time, there is increasing interest in the role that these private forests play in providing and maintaining habitat
for wildlife. Historically, timber production from these forests has been opportunistic, with little or no silviculture to
maintain wood production potential. Market circumstances and policy settings have not favoured sound silvicultural practice,
generating an exploitative and short-term view of the timber resource to maximise short-term returns. This has occurred at
a time when these forests are an important and increasing source of log supply to industry. This paper discusses payment of
biodiversity credits (incentives) to improve both environmental management and timber production outcomes, and examines the
findings of some recent studies on the ‘sustainability’ of PNF. Willingness-to-pay (WTP) and willingness-to-supply studies
reveal a disparity between the demand and supply prices for biodiversity and habitat ‘services’ in many cases. Recent ‘sustainability’
studies indicate forestry operations are relatively benign in their impacts on biodiversity, compared to other land uses.
However, in the absence of increased financial returns from PNF and in the face of increased public demand for greater environmental
outcomes, there seems little alternative to meeting the competing demands of biodiversity and timber production than to implement
a system of incentive payments which reward sound private forest management for a multiplicity of objectives.
相似文献
9.
This paper analyses industrial round wood flows into, within, and out of Northwest regions of Russia. We examine sawlogs, pulpwood, and fuelwood used for industrial purposes obtained from logging, and chips obtained from the wood-processing industry. We attempt to clarify different recent trends in wood harvesting, industrial round wood export, and forest industries development that have an influence on unreported wood in Russia. Our method, which uses wood balance diagrams, provides an interpretation of data from different Russian sources in order to offer better transparency regarding wood flows from forests to mills. It also helps to explain the apparent imbalance between round wood supply and demand and it helps one to assess the possible share of unreported industrial round wood production in Northwest Russia. Based on annual forest-related statistical data available from the Ministry of Natural Resources, the State Committee of Statistics, and the Russian Federation’s Customs Department, unreported round wood flows can be estimated to be 23% of the total industrial round wood production, or approximately 9 million m 3 u.b. per year. Unreported round wood flows are more common in export oriented regions that have poorly developed forest industries. 相似文献
10.
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• Effects of thinning on epicormics have rarely been demonstrated especially due to inaccurate surveying methods. 相似文献
11.
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• Canarian Juniper woodlands, now very scarce, are rich in endemic and endangered plants. However, many aspects of juniper
regeneration are almost unknown. 相似文献
12.
Der Wald ist für den Naturschutz
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— aus grunds?tzlichen Erw?gungen,
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— wegen seines hohen Wertes als Lebensraum für Pflanzen und Tiere,
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— im Hinblick auf seinen gro?en Fl?chenanteil, auch in seiner Form als Wirtschaftswald von besonderer Bedeutung.
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Die naturschutzfachlichen Anforderungen an eine naturvertr?gliche Waldbewirtschaftung lassen sich insbesondere mit Hilfe des
Arten- und Biotopschutzprogramms und anderer konzeptioneller Arbeiten immer besser formulieren; es bedarf aber noch weiterer
Grundlagenerhebungen, insbesondere einer ?kologischen Werterfassung im Wald. 相似文献
13.
The organization of wood cell wall components involves aggregates of cellulose microfibrils and matrix known as macrofibrils.
A combination of field emission electron microscopy and environmental scanning electron microscopy was used to visualise the
organization of macrofibrils in different cell wall types comparing normal and reaction wood of radiata pine and poplar as
examples of a typical softwood and hardwood. The size of macrofibrils is shown to vary among cell wall types with the smallest
structures occurring in the gelatinous layer of tension wood (14 nm) and the largest structures in the S2 L layer of compression wood (23 nm). A positive correlation between macrofibril size and degree of lignification is observed,
with macrofibrils apparently increasing in size in more highly lignified cell wall types. The fibrillar structure of the secondary
wall varies from microfibril-sized structures of 3–4 nm up to large aggregates of 60 nm diameter. The size of macrofibrils
also varies slightly among adjacent cells of the same cell wall type. Macrofibrils occur predominantly in a random arrangement,
although radial and tangential lamellae may sometimes be seen in individual cells.
相似文献
14.
The article introduces the background and summarises main research findings of the research articles in this special issue.
The focus is on the key issues relevant for forest-based entrepreneurship development in small-scale forestry in relation
to both wood and non-wood forest products and services (NWFP&S). The article draws special attention to changing forest ownership,
changing owners’ motives and values, and the evolving role of forest owners’ associations in Europe. The paper draws attention
to the finding that many small-scale forest owners do not treat their forest as an income-generating asset. The ownership
of the forests may be more important as symbolic capital than as a source of income. This is quite opposite to the traditional
wood production model that for instance most of the Forest Owners Association’s still follow. In relation to NWFP&S, the taxonomy
and indicators for NWFP&S are discussed and some conclusions from studies on forest recreation innovation and NWFP&S marketing
are presented. The NWFP&S sector is traditionally product-oriented, which is strategically peculiar because the long distances
from rural production areas to the customers would suggest highest orientation on marketing. Also surprising is the low level
of segmentation in the sector.
相似文献
15.
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• The effect of water stress on host selection and performance during the shoot feeding phase, by the Mediterranean pine shoot
beetle Tomicus destruens, was studied. 相似文献
16.
The effects of stocking on wood stiffness (MoE) for three Eucalyptus species are quantified using a 6-year-old trial established in New South Wales, Australia. An acoustic time-of-flight tool
measured the velocity between two probes in the outerwood, from which the stiffness was estimated. Four stocking levels (714,
1,250, 1,667 and 3,333 sph) were examined. Stiffness varied significantly between all species, with E. cloeziana showing the highest stiffness (14.2–15.7 GPa), followed by E. pilularis (12.2–13.5 GPa) and E. dunnii (10.7–12.6 GPa). There was a stiffness increase (around 11%) between 714 and 1,250 stems/ha for all species but thereafter
differences between stockings were not always significant. Trees were also assessed for basic density, dbh, total height, crown area, green crown height and stem slenderness (height/ dbh). Only stem slenderness had a significant association (0.41 ± 0.17) with stiffness. These findings suggest that, where stiffness
is a priority, forest managers could reduce establishment costs with low stockings (around 1,250 stems/ha).
相似文献
17.
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• Previous studies on competitive interactions among silver birch, Scots pine, and Siberian larch have not addressed the direct
importance of the species identity of nearby competitors. 相似文献
18.
After reunification in 1990, Germany’s forest cluster developed anew and employment in the wood-based industries differentiated
very quickly. With more than 900,000 employees, it is now considered one of the most important industrial sectors in the country.
This paper analysed general trends in the development of employment of wood-based industries in the German forest cluster
between 1999 and 2006. Shift-share analysis was considered to be the most appropriate way to determine regional differences
in the subsection DD/20 ‘Manufacture of wood and wood products’ of the code “Classification of Economic Activities in the
European Community, Revision 1.1” (NACE): the sawmill industry, the wood-based panel industry, the wood construction industry,
the wood-based packaging industry, and the miscellaneous wood products industry. This method decomposed the change of employment
into three different components that are due to that change: national trends, (industrial) sectoral trends, and regional conditions.
Employment in the selected wood-based industries showed a significantly larger decrease than overall trends in both the producing
industries and the whole economy of Germany: a continual loss of employees could be observed over the time period, affecting
almost all of the selected wood-based industries. However, federal states in western and eastern Germany experienced divergent
trends between 1999 and 2006, as different absolute and relative regional share components indicated in the shift-share analysis.
This method allows of identifying regional disparities and characterising regions with positive (mainly eastern federal states)
and negative (mainly western federal states) rates of employment growth. The research suggests that positive employment trends
in eastern Germany’s wood-based industries can mainly be attributed to regional factors such as comparatively higher subsidies
for new investments, lower labour costs, lower land values or infrastructural peculiarities.
相似文献
19.
Acoustics provide opportunities for non-destructive evaluation of the mechanical properties of wood, especially stiffness.
In this work, Fakopp 2D a time of flight (TOF) tool and WoodSpec a resonance-based system were used. In a scoping study on
young Pinus radiata trees (aged 8–11) no systematic differences were found between the Fakopp acoustic velocity on opposite sides of young trees.
These Fakopp values were then averaged and correlated with that from the equivalent log using WoodSpec. Finally stem and log
values were correlated with acoustic velocity in outerwood and in corewood lumber. External measurements on the log (standing
tree) correlated well with those for lumber cut adjacent to the bark and modestly for the corewood ( R
2 of 0.89 and 0.74, respectively). In a separate study, the acoustic velocities were measured on standing trees in three adjacent
stands aged 8, 16 and 26 and the data were used to construct a “Russian Doll” model to demonstrate the enormous range in wood
stiffness within and between trees. The stiffest 20% of the population was estimated to be 146, 87 and 76% stiffer than the
poorest 20% in the corewood (age 8), intermediate (age 16) and outerwood zone (age 26) respectively.
相似文献
20.
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• Fine root responses to potential climate change are relatively unknown in spite of their central role in ecosystem functioning. 相似文献
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