| – |
• This study investigated the short-term changes in neutral genetic variation that would occur if a mature, second-growth,
black walnut (Juglans nigra L.) stand was harvested following either a diameter-limited or value-limited cutting regime. 相似文献
2.
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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
3.
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• Considerable progress has been made recently to promote glue-laminated beams of European beech (Fagus sylvatica L.) for load-bearing structures in engineering. However, further investigations into the bond durability are required. The
objective of the present study was to analyse material and manufacturing factors and their combination to improve the resistance
in delamination tests as required for the use in building service class 1. 相似文献
4.
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• Multivariate statistical analysis was used to define different developmental stages for stone pine (Pinus pinea L.) considering tree size and cone production, without site-specific information. 相似文献
5.
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• The Spanish fir (Abies pinsapo Boiss.) is a conifer endemic to southern Spain and belongs to a Mediterranean basin group of firs considered to be relict.
Megagametophyte storage proteins are a useful tool for the evaluation of genetic variability due to the haploid nature of
megagametophytes in conifers. 相似文献
6.
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• Existing growth and yield plots of pure and mixed stands of Norway spruce (Picea abies (L.) H. Karst.) and European beech (Fagus sylvatica L.) were aggregated in order to unify the somewhat scattered sources of information currently available, as well as to develop
a sound working hypothesis about mixing effects. The database contains information from 23 long-term plots, covering an ecological
gradient from nutrient poor and dry to nutrient rich and moist sites throughout Central Europe. 相似文献
7.
Der Wald ist für den Naturschutz
| – |
— aus grunds?tzlichen Erw?gungen,
|
| – |
— 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.
|
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
8.
Die bisher erarbeiteten Ergebnisse lassen sich wie folgt zusammenfassen:
| 1. |
Bei der Fichte korrelieren Jahrringbreite und Holzdichte und damit die wesentlichen Festigkeitseigenschaften, wie Biegefestigkeit,
Biege-E-Modul, Druckfestigkeit.
|
| 2. |
Die Holzdichte als wesentliche Eigenschaft steht in enger Beziehung zum Sp?tholzanteil.
|
| 3. |
Die Astst?rke korreliert direkt mit der Wachstumsgeschwindigkeit, d. h. ebenfalls mit der Jahrringbreite.
|
| 4. |
Astst?rkensumme und Jahrringbreite zusammen erkl?ren einen gro?en Teil der technischen Holzeigenschaften.
|
| 5. |
Durch Wert?stung kann ein Teil der negativen Wirkungen des schnellen Wachstums auf die Festigkeitseigenschaften ausgeglichen
werden.
|
| 6. |
Dies bedeutet allerdings nicht, da? die Holzdichte als wesentliches Merkmal an Bedeutung verliert.
|
| 7. |
Eine weitgehend zu erwartende Reihung ist also aus holztechnologischer Sicht eindeutig festzustellen:
|
| – |
— engringig und wertge?stet auf dem 1. Platz, verspricht also h?chsten Holzwert,
|
| – |
— engringig, nicht wertge?stetes Holz steht an 2. Stelle,
|
| – |
— weitringig, wertge?stet im Mittelfeld, nur knapp nach Position 2
|
| – |
— weitringiges, nicht wertge?stetes Holz verliert, mit Abstand an letzter Stelle stehend.
|
Results achieved till now may be summarized as follows:
| 1. |
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.
|
| 2. |
Wood density as an essential property is closely related to the share of late wood.
|
| 3. |
There is a direct correlation between knot size and growth rate, i. e. also annual ring width.
|
| 4. |
The sum of knot diameters and annual ring width together explain a large part of the technical wood properties.
|
| 5. |
High pruning may compensate for some of the negative effects of rapid growth on strength properties.
|
| 6. |
This, however, does not imply that wood density is becoming less important as an essential property.
|
| 7. |
From the wood-technological viewpoint, a largely to be expected ranking can be clearly established:
|
| – |
— narrow growth rings and high-pruned stands in first place, thus promising the highest timber value,
|
| – |
— narrow growth rings but not pruned comes second,
|
| – |
— wide growth rings and high-pruned ranks about in the middle, only slightly behind position 2,
|
| – |
— wood showing wide growth rings and not being from pruned trees falls way behind.
|
相似文献
9.
| – |
• Increased mortality of Scots pine (Pinus sylvestris L.) and spreading of deciduous trees are observed in the Swiss Rhone valley. Previous research identified climate change
effects as main drivers of this trend. On the local scale, we hypothesize that legacies from past anthropogenic disturbances
are superimposed on climate effects. 相似文献
10.
| – |
• We present the results of a two-year (2007–2008) greenhouse study investigating the effect of water availability and nitrogen
fertilization on the growth, biomass partitioning, and foliar nutrient content of Abies fraseri (Pursh) Poir. 相似文献
11.
| – |
• We combined stem volume increment analysis with dendroecological tools to address two unresolved issues concerning oak dieback
in Mediterranean areas: early detection of changes in stand growth, and identification of mechanisms for observed growth declines. 相似文献
12.
| – |
• Paternity was established in a field trial of Abies nordmanniana with open-pollinated (OP) offspring from a clonal seed orchard (CSO) comprising 23 clones. 相似文献
13.
| – |
• 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
14.
| – |
• Carbon isotope composition (δ13C) is a complex trait involved in acclimation, adaptive processes and related to water use efficiency (WUE) and/or productivity. 相似文献
15.
| – |
• Tree mortality is an important process in forest ecosystem dynamics and is one of the least understood phenomena, because
of the complex interactions between different environmental stresses, minimal understanding of whole-plant mortality processes,
and a chronic shortage of data. 相似文献
16.
| – |
• 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
17.
| – |
• 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
18.
| – |
• The aim of our work was to homogenise the meteorological dataset of German ICP Forests Level II sites (n = 73) by the aid of interpolations based on climate data from the German meteorological network (DWD). 相似文献
19.
| – |
• Plantation forestry in Zambia is based mainly on non-native Eucalyptus and Pinus species and constitutes an important component of the country’s economy. The productivity of these plantations is, however,
threatened by several factors, including fungal pathogens that reduce timber quality and cause tree mortality. 相似文献
20.
| – |
• We studied the effects of acorn cotyledon loss by insect damage and artificial excision on germination and seedling survival
of Quercus variabilis, to determine whether insect infestation decreases acorn germination and seedling establishment; and to what extent cotyledon
damage can affect acorn germination and seedling establishment. 相似文献
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