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991.
Variations in soil chemical properties and microbial biomass in artificial gaps in silver fir stands
Changes in soil chemical and microbiological parameters in small (185 m2) and medium (410 m2) gaps, created in mature silver fir (Abies alba Mill) stands (mean height 30 m) in the Calabrian Apennines (Southern Italy), were studied over 2 years. Medium gaps had high
soil temperature and photosynthetically active radiation (PAR) transmittance and low soil moisture. Within small gaps we detected
a greater amount of organic matter, with respect to under canopy cover sites and medium gaps. Moreover, a different trend
of the organic matter between small and medium gaps was observed. In the medium gaps, with respect to under canopy cover sites
and small gaps, we found a relatively low content of organic matter, associated to a lower amount of humic acid, which suggested
that the organic substrate undergoes a mineralization rather than a humification process. An opposite trend was observed in
small gaps, where the increase of organic matter content, associated to an increase of humic acid and microbial biomass, suggested
a better humification process. Moreover, in small gaps the highest level of urease and the greatest fluorescein diacetate
(FDA) hydrolysis were observed. The different trend of organic matter observed in small and medium gaps may be related to
changes in the environmental conditions. PAR transmittance, significantly higher in medium gaps, contributed to increase soil
temperature and decrease soil moisture, affecting soil microbial populations and organic matter trend. These results suggest
that the creation of small gaps represents the silvicultural practice with minor environmental impact. 相似文献
992.
Seeds of Juniperus procera collected from five provenances across its geographic range in Ethiopia were subjected to cold-moist stratification at 5°C
or 10°C for 6–12 weeks. The effect of aqueous smoke solution in overcoming the light requirement for germination, and the
potential of visible (VIS) and near infrared reflectance (NIR) spectroscopy for sorting sound and insect-damaged seeds were
also investigated. Highly significant differences in germination were detected among provenances (P < 0.0001) and stratification periods (P < 0.0001), but not between temperature regimes (P=0.111). Seeds from the south and southeast distribution ranges had higher percentage germination after 6 weeks of stratification
than seeds collected from north, northwest and central ranges of distribution. The smoke treatment did not affect germination
regardless of whether the seeds were exposed to light. Exposure to light increased germination capacity three fold. Sound
and damaged seeds were distinguished with 90% accuracy using VIS + NIR spectroscopy. It can be concluded that dormancy in
juniper seeds varies with provenances, and cold stratification for 6 weeks alleviates dormancy in some seed lots. Tentatively,
smoke treatment seems ineffective in overcoming photo-dormancy in juniper seeds. VIS + NIR spectroscopy has demonstrated a
great potential for sorting damaged seeds, thereby upgrading seed lot purity. 相似文献
993.
Kuniyoshi Shimizu Shoko Fukunaga Keisuke Yoshikawa Ryuichiro Kondo 《Journal of Wood Science》2007,53(2):153-160
The effects of 120 methanol extracts prepared from bark and heartwood of 69 types of Japanese wood on the melanin production
of B16 melanoma cells were examined. The melanin content of B16 melanoma cells was determined spectrophotometrically at 405nm.
The extracts were also examined for their effects on cell viability. We found that the methanol extracts of Fagus crenata (buna, wood, 100μg/ml), Sapium sebiferum (Nankinhaze, wood, bark, 10μg/ml), and Zelkova serrata (keyaki, wood, 10μg/ml) greatly inhibited the melanin production of B16 melanoma cells without significant cytotoxicity.
However, these extracts did not inhibit tyrosinase activity at the concentration of 100μg/ml. These findings indicate that
the depigmenting mechanism of these extracts involves the suppression of some pigmenting signals in stimulating melanogenesis
rather than the inhibition of tyrosinase activity.
Part of this study was presented at the 53rd Annual Meeting of the Japan Wood Research Society, Fukuoka, Japan, March 2003 相似文献
994.
Hiroto Homma Hirofumi Shinoyama Yukihiro Nobuta Yoshie Terashima Seigo Amachi Takaaki Fujii 《Journal of Wood Science》2007,53(1):80-84
Strobilurus ohshimae is an edible mushroom, and it specifically forms its fruiting bodies on buried sugi (Cryptomeria japonica) twigs. In this research, we studied lignindegrading activity of S. ohshimae. We isolated 18 strains of S. ohshimae from various regions of Japan, and determined their lignin degradation rates on sugi wood meal medium. All the strains of
S. ohshimae degraded approximately 6%–12% of sugi lignin in 30 days, and these lignin degradation rates were 1.5–3 times higher than those of Trametes versicolor, which is a typical lignin-degrading fungus. Among the three main lignin-degrading enzymes, activity of lignin peroxidase
and manganese peroxidase was not observed, while 4340U/g of laccase was produced in 30 days. To investigate the effect of
wood species on lignin degradation by S. ohshimae, the lignin degradation rate and laccase productivity on sugi wood meal medium were compared with those on beech (Fagus crenata). In T. versicolor, both lignin degradation rate and laccase productivity were higher on beech than on sugi. Conversely, in S. ohshimae, lignin degradation rate and laccase productivity were higher on sugi than on beech. Therefore, it was suggested that coniferous lignin is not always difficult to degrade for the fungi that inhabit
softwood.
Part of this article presented at the 54th Annual Meeting of the Japan Wood Research Society, Sapporo, August 2004 相似文献
995.
Natacha Guérard Pascale Maillard Claude Bréchet François Lieutier Erwin Dreyer 《Annals of Forest Science》2007,64(6):601-608
Three-year-old saplings of Pinus sylvestris L. were labeled with 13CO2 prior to inoculating the trunk with Ophiostoma brunneo ciliatum, a blue-staining fungus usually associated to Ips sexdentatus. During incubation, half the trees were submitted to a severe drought that decreased photosynthesis and natural 13C content in non-labeled saplings. A large 13C-excess was obtained in wood and phloem, especially in the fractions of soluble proteins, starch and soluble sugars of labeled saplings. Drought increased 13C-excess, due to reduced photosynthesis and smaller dilution of 13C by the addition of newly assimilated 12C. The induced-reaction zones in inoculated saplings displayed large total C (58 g 100 g?1) because of the accumulation of secondary metabolites. They also showed much larger 13C-excess than any other compartment: the contribution of stored C to the reaction zones was much higher than that of currently assimilated C. Moreover, drought lowered the contribution of the latter, as shown by the increase of 13C in the reaction zones. We conclude that stored C was readily mobilized for the construction of reaction tissues, and that the contribution of currently assimilated C was only minor. 相似文献
996.
Xiaoxi Zhang Zengwen Liu Bochao Zhu Yuanhao Bing Nhu Trung Luc Liangzhen Du Zhenhua Zhu 《林业研究》2016,27(3):525-532
The productivity of Robinia pseudoacacia (R.p.) pure forest usually declines at the late growth stage, and reforming it into mixed forests could be a promising way to resolve this problem. When choosing a suitable tree species that can be mixed with R.p., the interspecific relationship is an important issue. Therefore, we gathered the autumn litter fall from R.p. and 10 other species from the Loess Plateau of China were mixed in dual species litterbags (R.p. + each other species) and buried them in soil for a 345 days lab decay incubation. We measured the litter mass loss and nutrient contents to determine whether the nutrient release was affected by mixed species litter decomposition. The impacts of mixed litter decomposition on macro-elements release were more obvious than on micro-elements. The litters with similar substrate quality might show variable impacts on nutrients release in mixed decomposition. The C loss and release of nutrient was improved by descending order when R.p. litter was mixed with Hippophae rhamnoides, Ulmus pumila, Populus simonii, Larix principis-rupprechtii and Quercus liaotungensis (Q.l.). But, except for Q.l., only the other species were recommended as suitable mix-plants for R.p. since promoting a high turnover of the nutrient in the litter compartment and a rapid availability for tree. 相似文献
997.
The current state of cooperation in private forestry in Lithuania is examined, with a focus on the analysis of objectives,
organisational structure and the ways forest owners’ cooperatives operate. A postal survey has been used as a main research
instrument, the questionnaire consisting of a series of multiplechoice close-ended questions. This paper provides insights
into the state forest enterprises and other private companies operating in the private forestry sector, and places forest
owners’ cooperatives in a broader context of the private forestry sector. A typical forest owner’s cooperative in Lithuania
has up to 10 members and about 20 clients to whom services are provided. The leaders of cooperatives indicate that the optimal
number of clients using their services should not exceed 40. The main stated objectives of cooperatives are the provision
of services to their members under the most attractive conditions, uniting members, and earning a profit for the members.
These activities of cooperatives revolve around timber harvesting and trade. It is concluded that the process of cooperation
of private forest owners in Lithuania is rather slow, although positive development can be observed. 相似文献
998.
999.
The fatigue behavior of plywood specimens under shear through thickness was examined on the basis of strain energy to obtain
common empirical equations for the fatigue process and failure criterion under various loading conditions. Specimens were
cut from commercial plywood panels of 9-mm thickness. Loading conditions were set as follows: a square waveform at a loading
frequency of 0.5 Hz, a triangular waveform at 0.5 Hz, and a triangular waveform at 5.0 Hz. Peak stress applied was determined
to be 0.5, 0.7, and 0.9 of static strength, that is, stress levels of 0.5, 0.7, and 0.9. The stress-strain relationships were
measured throughout the fatigue test, and the strain energy was obtained at each loading cycle. Loading conditions apparently
affected the relationship between stress level and fatigue life. On the other hand, the relationship between mean strain energy
per cycle and fatigue life was found to be independent of loading conditions. Mean strain energy per cycle obtained as the
fatigue limit was 5.85 kJ/m3 per cycle. Assuming that the accumulation of strain energy is a fatigue indicator, the fatigue process and failure criterion
for the plywood specimens under the three loading conditions were commonly expressed by the relationship between cumulative
strain energy and loading cycles. 相似文献
1000.
The three-dimensional structure of a transverse sawn wood surface was investigated using several methods, to compare techniques,
and to study the types of deformation in tracheids at the saw cut. A sample of spruce sapwood was cut with a fret saw across
the grain. The transverse sawn surface was imaged by confocal microscopy, field emission scanning electron microscopy (FESEM),
and by light microscopy combined with serial sectioning and three-dimensional (3D) reconstruction. Both confocal microscopy
and FESEM were restricted to visualising the cut surface of the wood. However, serial sectioning was able to reveal the internal
structure below the cut surface providing more information on the types of cell deformation present. The wood structure was
deformed to depths of more than 600 μm below the surface with twisting, crushing and tearing deformations. Near the outer
surface, gaps were formed between groups of tracheids where the cell walls had been torn away to form saw dust. The deformation
tended to form groups of tracheids that were twisted relative to each other. Latewood was less distorted, forming a dense
solid surface compared to the highly fibrous earlywood. 相似文献