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981.
To better understand tree regeneration trajectories and the resultant coexistence of Abies with co-dominants, Picea jezoensis var. hondoensis, Tsuga diversifolia and Betula ermanii, in an old-growth subalpine forest, we investigated spatial mortality patterns during the regeneration of Abies mariesii and A. veitchii, which are abundant in the understory reflecting their shade tolerance. Regeneration of these Abies spp. from shaded understory to canopy status is affected by other canopy co-dominants. Snags of understory Abies spp. were common, suggesting that the primary mortality agent is suppression by the overstory. Although live, small Abies trees in the understory were positively associated with a Picea canopy, the long-term survival was reduced among Abies trees close to the canopy, suggesting that shading by large Picea in the overstory negatively affects understory Abies plants. The existence of shade-intolerant canopy co-dominants such as Picea and also Tsuga, which are larger and longer lived than the shade-tolerant Abies, may play an important role in preventing the Abies spp. from competitively displacing these other tree species, which are much rarer in the understory, though common in the canopy. Moreover, in spite of the fact that Betula canopies fostered recruitment and growth of Abies saplings, Abies showed no association with Betula canopy and their survival at later-stage was rather reduced near or beneath Betula canopies at the subsequent understory small tree stage. Based on spatially significant events related to tree death, this study detected such “habitat shifts” in the trajectory of tree regeneration. Accordingly, it can be concluded that careful consideration of the regeneration habitat is required for a fuller understanding of ecological processes in spatially complex old-growth forest systems. 相似文献
982.
Since Gruner's pioneer work in 19341), vermiculite has been attracting the attention of mineralogists and soil scientists with much interest, probably because of its unique behaviour on cation exchange and of a component common in most soils derived from various parent rocks. A number of papers thereafter dealt with the mineral, revealing its properties, diagenesis, and distribution in soils. However, as information has been accumulated on vermiculite, especially on clay vermiculite, it became evident that the difference between vermiculite and montmorillonite is due simply to the difference in layer charge and that the division is essentially an arbitrary one2). Walker suggested that the Mg plus glycerol test would be the only one which appeared to be universaIlY valid in the identification of vermiculite, and that although the K test was still of value as an aid in the differentiation, it could no longer be reo commended as of universal validity. In recent years, several workers4-12) indicated that interlayer materials, especially Al-hydroxyls, prevented vermiculite from contracting to 10 Å in the K test and prevented montmorillonite from expanding to 18 Å in the Mg-glycerol test. This suggests that in the light of new evidences the 14 Å mineral hitherto believed as vermiculite, chlorite, or montmorillonite by the classical test should be reexamined after removal of interlayer materials. 相似文献
983.
Hiroshi Yoshihara Yoshitaka Kubojima Koji Nagaoka Masamitsu Ohta 《Journal of Wood Science》1998,44(1):15-20
When measuring the shear modulus of wood by static bending tests, the basic theory is dependent on Timoshenko's bending theory. The shear modulus obtained by static bending is a much smaller value than that derived by other methods. We examined the applicability of Timoshenko's theory and propose an empirical equation that can derive the shear modulus properly. Three softwoods and three hardwoods were used for the tests. First, the Young's modulus and shear modulus were measured by free-free flexural vibration tests. Then the three-point static bending tests were undertaken, varying the depth/span ratios. Additionally, the bending tests were simulated by the finite element method (FEM). The shear moduli obtained by these methods were then compared. The deflection behaviors in static bending were not expressed by the original Timoshenko bending theory because of the stress distortion near the loading point. Based on the experimental results and numerical calculations, we modified the original Timoshenko bending equation. When using our modified equation the stress concentration must be carefully taken into account. 相似文献
984.
Tadashi Sakai Hisashi Murata Makoto Endo Toshiyuki Shimomura Kiyoshi Yamauchi Takafumi Ito Tokio Yamaguchi Hiroshi Nakajima Mikio Fukudome 《Aquaculture (Amsterdam, Netherlands)》1998,160(3-4):205-214
The jaundiced yellowtail Seriola quinqueradiata had yellow discolored skin and hyperbilirubinemia. Histology revealed that hemosiderin and ceroid occurred in the spleen. In the vascular system, there were vasculitis and sinusoidal dilatation. Hepatic cells showed degenerative figures with pyknotic or karyolytic nuclei, basophilic cytoplasm, cytoplasmic vacuoles in various sizes, and ceroidosis. In the bile duct system, however, there was no noticeable change. Hemoglobin contents of jaundiced fish were similar to those of control fish. Plasma taurine levels of jaundiced fish were significantly lower than those of control (p0.05). Judging from 2-thiobarbituric acid reactive substance values, in vivo lipid peroxidation progressed in the liver of jaundiced fish. In the plasma of jaundiced fish, contents of unconjugated bilirubin were significantly higher than those of conjugated bilirubin. A large amount of substance Xs, breakdown products of bilirubin scavenging active oxygen species, existed in the plasma of jaundiced fish. Therefore, jaundiced fish may suffer from severe oxidative stress, which might be a principal cause of jaundice. Liver superoxide dismutase and glutathione peroxidase activities of jaundiced yellowtail were significantly lower than those of controls. 相似文献
985.
We investigated the origin of dissolved free amino acids (DFAA) in stream water focusing on biofilms in the river bed by means
of incubation experiments in the laboratory. Stones were placed in the Toyohira River, Hokkaido, Japan, for 3 months, allowing
formation of biofilms, and then incubated for 24 h in the laboratory at stream water temperature. After incubation, the composition
and concentrations of DFAA in the incubation solution and total hydrolyzed amino acids (THAA) in biofilms were measured by
high-performance liquid chromatography. The amount of chlorophyll a (Chl. a) and the number of bacteria were also measured. The DFAA concentration increased greatly in the biofilm incubation solution,
but the DFAA composition (mol %) did not change relative to the inception of incubation, where it was similar to stream water.
There was no correlation between the increase in DFAA concentration and the THAA concentration, Chl. a amount, or the number of bacteria in biofilms. These results suggest that biofilms are one of the major sources of DFAA in
stream water. 相似文献
986.
Yoichi Miyake Shingo Kimura Tomohiko Kawamura Takashi Kitagawa Motoyuki Hara Hiroshi Hoshikawa 《Fisheries Science》2010,76(4):561-570
Most juveniles of Haliotis discus hannai have been found to be descendants of wild individuals, although most adults were artificially produced (released) individuals
as a result of restocking inside the refugium located near the head of Oshoro Bay, Hokkaido, Japan. To estimate the larval
supply from released and wild individuals into the refugium and to compare the suitability of locations as larval sources,
we simulated larval dispersal using a coupled hydrodynamic and particle-tracking model. The simulation results indicated that
more larvae may be supplied from the wild adults inside the bay to the refugium than from the released adults. These results
are consistent with the observed high abundance of wild juveniles in the refugium. Most larvae from the refugium were predicted
to disperse out of the bay. We found that larval retention in the bay was at least one order of magnitude higher than that
in the refugium. Thus, it may be more effective in terms of self-replenishment and reproduction if the refugium were to be
expanded to the bay scale. There were only minor differences among the compared sites at the head of the bay in terms of their
suitability as larval sources. Consequently, the establishment of new refugia in this area could be expected to provide an
effectiveness equal to that of the current refugium. 相似文献
987.
Vu Minh DUC Rina KAKIUCHI Takeshi OBI Hiroshi ASAKURA Takehisa CHUMA 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2022,84(3):414
This study aimed to analyze the incidence of Campylobacter in a small-scale chicken meat processing plant producing “chicken-sashimi”, and determine the effectiveness of surface burning as a treatment during processing. The most probable number (MPN) method was used to analyze the load of Campylobacter in 48 samples from four different processing steps (de-feathering, chilling, surface burning, and final-products; 12 samples each). We found the highest load of isolated bacteria in chicken skin after de-feathering. Campylobacter was not detected after the surface burning step despite a large load of bacteria present in the cecum content. Campylobacter was absent in the final products. Adequate surface burning can avoid Campylobacter contamination of chicken sashimi in the processing plant by applying the external stripping method. 相似文献
988.
989.
Evaluation of aroma compounds contributing to muskmelon flavor in Porapak Q extracts by aroma extract dilution analysis 总被引:1,自引:0,他引:1
Hayata Y Sakamoto T Maneerat C Li X Kozuka H Sakamoto K 《Journal of agricultural and food chemistry》2003,51(11):3415-3418
The flavor of the Miyabi variety of Japanese muskmelon was extracted according to the Porapak Q column method (PQM) and evaluated by using aroma extract dilution analysis (AEDA) method. The overall odor of the PQM extracts was perceived as having a natural muskmelon-like odor, suggesting that the PQM was able to extract volatile compounds in muskmelon fruit without degradation of original flavor. Forty-six odorant compounds [Kovats index (KI), 961 < or = KI < or = 2605] were found by GC-sniffing in PQM extracts, confirming the effectiveness of PQM in trapping a wide range of volatile compounds in muskmelon flavor. The 46 odorants could be divided into three groups on the basis of their odor attributes: fruity note (KI < 1300); green, grassy, or cucumber-like note (1300 < KI < 2020); and sweet note (KI > 2020). When the original extracts were diluted in AEDA analysis, seven odorants could still be detected by GC-sniffing at a flavor diluation (FD) factor of 128 or above: one had a fruity note (compound 3); four had a cucumber-like, green, or grassy note (compounds 12, 17, 21, and 23); and two had a sweet note (caramel-like or yakitori-like) (compounds 32 and 34). 相似文献
990.