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151.
The conversion of anthropogenic into more natural, self-regenerating forests is one of the major objectives of forestry throughout
Europe. In this study, we present investigations on permanent plots with different silvicultural treatment in NE German pine
stands. Management of old-growth pine stands on acidic and nutrient-poor sandy sites differs in fencing, thinning, and planting
of certain tree species. The investigations were carried out on the community, population, and individual level of the pine
forest ecosystems. Thus, vegetation changes, size and height of tree populations, and height increment of tree individuals
were observed over a time span of 6 years. Special attention was paid to short-lived tree species such as, e.g., Frangula alnus and Sorbus aucuparia, as well as to Fagus sylvatica as one of the most typical forest tree species of Central Europe. Vegetation changes are interpreted as a consequence of
natural regeneration of formerly degraded forest sites, involving an increase in nutrient availability. High browsing pressure
can be considered as a key factor for the inhibition of tree seedlings and growth of saplings. Some Sorbus aucuparia individuals, however, succeeded in growing out of the browsing height also in unfenced stands. Few found specimens of Fagus sylvatica proved that this species is able to establish spontaneously on these relatively dry, acidic sites under continental climate
influence. Such natural regeneration processes, also including spontaneous rejuvenation of trees, can be integrated into silviculture
as passive forest conversion management. An active management like thinning of stands, planting of trees, and fencing can
accelerate forest conversion with regard to height growth and species number of trees. 相似文献
152.
Wood samples of apitong (Dipterocarpus grandiflorua) and ilang-ilang (Ilang-Ilang C. dadloyi) and feces of termites [Cryptotermes brevis (Walker)] fed on these woods were collected from University of the Philippines, Los Baňos. Lignin of each sample was isolated by Björkman’s procedure. There was no significant difference in 1H nuclear magnetic resonance (NMR) spectra or in the methoxyl content between Björkman lignins from original woods and termite feces. Differences were detected in the contents of aliphatic and unconjugated phenolic hydroxyl groups, suggesting minor structural changes of lignin during digestion by termites. In addition, the ratio of syringyl to guaiacyl nuclei of Björkman lignin from termite feces determined by 1H NMR spectra was higher than those from the original woods. The molar ratio of syringyl to guaiacyl nuclei of termite feces was higher than those from the original woods as determined by alkaline nitrobenzene oxidation. These results suggest that the structural changes of lignin in the termite gut are due to the insignificant formation of C-C linkages in guaiacyl nuclei. It was concluded that there were minor changes in the structural features of lignin under mostly anaerobic conditions, in contrast to the significant changes that occur through biological modification under aerobic conditions. 相似文献
153.
Kenji Ono Motohiro Hasegawa Makoto Araki Masahiro Amari Masakazu Hiraide 《Journal of Forest Research》2007,12(4):255-261
We examined the relationships between the absorptional characteristics in the near infrared region and the chemical changes
of decomposing beech (Fagus crenata) and pine (Pinus densiflora) litters. Spectra as well as the concentrations of chemical substances approached each other and converged with decomposition,
although both initial characteristics differed markedly between beech and pine. This indicated that the fundamental chemical
structures were almost the same, although their organochemical composition differed. Specific absorption bands for lignin,
polysaccharide, and protein were identified at 2,140 and 1,670 nm, 2,270, 1,720, 1,590, and 1,216 nm, and 2,350 nm, respectively.
Absorbance at 1,670 nm, peculiar band of aromatics, showed a positive correlation with lignin concentration, which suggested
the relative increment of aromatics due to condensed lignin in decomposing litters. Absorbance at 2,140 nm, characterized
as the C–H bond in HRC = CHR, showed a negative correlation with lignin concentration, which suggested the decrements of some
structures such as side-chains in lignin polymers unrelated to aromatics. Absorbance at 2,270, 1,720, and 1,216 nm, specified
to O–H/C–O/C–H bonds in saccharide, might reflect the change of polysaccharide during decomposition because they showed a
positive correlation to polysaccharide concentration. In the same way, absorbance at 2,350 nm, identified to the C–H/CH2 bonds in protein, showed a negative correlation to nitrogen concentration in decomposing litters, which might indicate that
the C–H/CH2 bonds in protein decreased with decomposition due to microbial consumption of carbon in protein. Our findings suggested the
possibility that the spectral changes indicate the litter digestibility during decomposition and that also explain the compositional
change in decomposing litters. 相似文献
154.
Tatsuhiko Yamada Masako Aratani Satoshi Kubo Hirokuni Ono 《Journal of Wood Science》2007,53(6):487-493
Degradation and decomposition of cellulose were studied in an acid-catalyzed solvolysis treatment of biomass using polyethylene
glycol (PEG) and ethylene carbonate (EC). The solvolysis reaction was followed by a typical reaction system of wood liquefaction
that uses sulfuric acid catalyst at 140° or 150°C at atmospheric pressure. The methods of fractionation and chemical analysis
of the degraded cellulose in the solvolyzed product are discussed. The solvolyzed product was separated into several fractions,
and they were hydrolyzed to release glucose and levulinic acid to determine the quantity of glucosides and levulinates in
the solvolysis product. The data clearly showed that the solvolysis reaction had the same mechanism when using PEG or EC.
Degradation of cellulose leads to the formation of glucosides, which then decompose, resulting in a levulinic acid structure,
and producing a water-insoluble fraction. The conversion rates of both glucosides and levulinates strongly depend on the reaction
conditions of the solvolysis. In particular, EC promotes faster conversion of the reactions. The method discussed here is
a chemical analytical technique for characterization of the products of wood liquefaction. 相似文献
155.
Movement of polyethylene glycol (PEG) 1000 from wood cell lumens into adjacent cell walls was studied for different cell wall
moisture contents (MCs) and PEG solvents; relative amounts of PEG that penetrated into the cell walls were estimated by Raman
microscopy. It was shown that samples treated with PEG from chloroform solution adsorb less PEG than samples treated with
PEG-water solution even in the case of samples with open cell wall structure near fibre saturation point MC. Reconditioning
of PEG-chloroform treated samples at high relative humidities enhanced PEG bulking of cell walls, but not to the maximum amounts
observed with PEG-water treatments. Raman microscopy was a useful tool for estimating relative PEG amounts in the cell walls. 相似文献
156.
Tian-Xiao Meng Shoko Furuta Sayaka Fukamizu Ryoko Yamamoto Hiroya Ishikawa Enos Tangke Arung Kuniyoshi Shimizu Shoji Ohga Ryuichiro Kondo 《Journal of Wood Science》2011,57(5):452-458
Pleurotus citrinopileatus Singer has recently become a popular delicacy in East Asian countries. We prepared a methanol extract, soluble fractions
from the methanol extract, and a hot water extract of the fruiting bodies of P. citrinopileatus. The biological activities such as melanin biosynthesis inhibition, tyrosinase inhibition, antioxidant activities [1,1-diphenyl-2-picrylhydrazyl
(DPPH) radical scavenging, oxygen radical absorbance capacity (ORAC), and superoxide dismutase (SOD)-like activity], antibacterial
activities, and antihyaluronidase activities of these extracts were evaluated. We found that the n-hexanesoluble, diethyl ether-soluble, and ethyl acetate-soluble fractions exhibited melanin biosynthesis inhibition in B16
melanoma cells, as well as antioxidant (ORAC) and antibacterial activities. However, the n-butanol-soluble and water-soluble fractions and the methanol and hot water extracts exhibited antioxidant (DPPH radical scavenging,
SOD-like activity) and antihyaluronidase activities. These results indicate that the fruiting bodies of P. citrinopileatus have the potential to be used as an ingredient in skin cosmetics. 相似文献
157.
Maria Margarida Ribeiro Leopoldo Sanchez Carla Ribeiro Fátima Cunha José Araújo Nuno M. G. Borralho Cristina Marques 《Annals of Forest Science》2011,68(4):701-714
• Introduction
Tree genetic improvement programs usually lack, in general, pedigree information. Since molecular markers can be used to estimate the level of genetic similarity between individuals, we genotyped a sample of a Portuguese Eucalyptus globulus breeding population—a reference population of 125 individuals—with 16 microsatellites (SSR). 相似文献158.
Frauke Kleemann Maximilian von Fragstein Barbara Vornam Annika Müller Christoph Leuschner Andrea Holzschuh Teja Tscharntke Reiner Finkeldey Andrea Polle 《European Journal of Forest Research》2011,130(5):707-716
Knowledge on phenological, morphometric, and phytochemical variation of local progenies of European aspen (Populus tremula, L.) is limited. The goal of this study was to characterize variation in growth and ecologically important leaf properties
in aspen full-sib families in relation to interacting organisms (mycorrhiza, endophytes, and insects) and to determine whether
these interactions were affected by soil application of a systemic fungicide. In local progenies, within-family variation
of neutral molecular genetic markers (nuclear microsatellites) was higher than between families. Significant variation in
growth, production of phenolic defensive compounds and other phytochemical leaf traits was found between families. Phenolic
compounds showed clear negative correlation with generalist herbivores, but did not result in negative trade-off with biomass
production. Differences in mycorrhizal colonization were not found among full-sib families and application of a systemic fungicide
suppressed neither mycorrhizal colonization nor infestation with insects. However, a strong suppression of endophytes occurred,
whose long-term consequences may require attention when fungicides are used in agroforestry plantations. 相似文献
159.
An air-injection press, which has holes punched in the heating plates, injects high-pressure air through the holes of one
plate into boards during press heating. The air-injection press can manufacture boards from high-moisture-content particles
by controlling blowouts of the boards. In this study, boards were manufactured from particles that had a moisture content
of 25% by using the air-injection press, which reduced the required pressing time. Boards manufactured by injecting air through
holes of 5 mm in diameter were of poor quality with a low internal bond strength of only 0.31 MPa. When the hole diameter
was reduced to 1 mm, the internal bond strength increased to 0.44 MPa. A high air-injection pressure of 0.55 MPa also resulted
in improved board properties over those for boards manufactured at lower pressures. This was probably because a large amount
of binder was released from boards through the 5-mm holes, together with water vapor, during air injection; the small-diameter
holes reduced the release of binder, resulting in better board properties. 相似文献
160.
Commercial Tectona grandis plantations using clones have attracted considerable interest for lumber production in tropical regions where small areas
are frequent. However, studies on wood properties are limited. Therefore, the purpose of this study is to group clones with
similar wood color characteristics using the CIELab system, and mechanical resistance by dynamic stiffness (Ed) in order to obtain different types of clones for different climate and edaphic conditions. It was found that lightness (L*), yellowness (b*), redness (a*), and Ed are similar to those found for other plantation trees. These wood characteristics are significantly influenced by clone and
site. Variance due to clone and site went from 31 to 53% and from 2.95 to 24.22%, respectively. Another source of variance
was distance from pith, with the exception of parameter b*, which was not affected. Finally, clones were grouped (using multivariate analysis) according to color and mechanical resistance.
This analysis established 4 groups by color and 5 groups by Ed. Clone clustering will allow us to choose or use clones with similar wood properties according to site and environmental
conditions increasing area production and wood quality uniformity. 相似文献