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31.
32.
Climate and vegetation history of the midcontinent from 75 to 25 ka: A speleothem record from crevice cave, missouri, USA 总被引:3,自引:0,他引:3
Four Missouri stalagmites yield consistent overlapping records of oxygen and carbon isotopic changes and provide a climate and vegetation history with submillennial resolution from 75 to 25 thousand years ago (ka). The thorium-230-dated records reveal that between 75 and 55 ka, the midcontinental climate oscillated on millennial time scales between cold and warm, and vegetation alternated among forest, savanna, and prairie. Temperatures were highest and prairie vegetation peaked between 59 and 55 ka. Climate cooled and forest replaced grassland at 55 ka, when global ice sheets began to build during the early part of Marine Oxygen Isotope Stage 3. 相似文献
33.
Japanese oak wilt causes widespread oak mortality in Japan. Possible differences in susceptibility to the causal fungus, Raffaelea quercivora, may be due to vessel arrangements in host trees. To clarify whether constitutive defence mechanisms including vessel arrangements or induced defence mechanisms are the main determinants of host susceptibility, we inoculated the fungus into living seedlings or sterilized stem segments of four Japanese fagaceous species. In seedlings, water conductance was assessed with dye. In both seedlings and stem segments, hyphal growth was examined by fluorescence microscopy. In seedlings, the area of non‐conductive sapwood in stem cross sections and hyphal growth differed significantly among species. In the susceptible species Quercus crispula and Quercus serrata, hyphal growth was significantly and positively correlated with the proportion of non‐conductive sapwood. In stem segments, hyphal growth was not significantly different among species or between vessel arrangements and was similar to or greater than that in seedlings. These results suggest that the extent of sapwood colonization by R. quercivora could be used as a marker for susceptibility and that susceptibility is determined mainly by induced defence responses. 相似文献
34.
Satoh R Kaku A Satomura M Kohori M Noura K Furukawa T Kotake M Takano T Hohdatsu T 《Journal of Feline Medicine and Surgery》2011,13(6):427-435
Feline infectious peritonitis virus (FIPV) can cause a lethal disease in cats, feline infectious peritonitis (FIP). The antibody-dependent enhancement (ADE) of FIPV infection has been recognised in experimentally infected cats, and cellular immunity is considered to play an important role in preventing the onset of FIP. To evaluate the importance of cellular immunity for FIPV infection, monoclonal antibodies (MAbs) against feline interferon (fIFN)-γ were first created to establish fIFN-γ detection systems using the MAbs. Six anti-fIFN-γ MAbs were created. Then, the difference in epitope which those MAbs recognise was demonstrated by competitive enzyme-linked immunosorbent assay (ELISA) and IFN-γ neutralisation tests. Detection systems for fIFN-γ (sandwich ELISA, ELISpot assay, and two-colour flow cytometry) were established using anti-fIFN-γ MAbs that recognise different epitopes. In all tests, fIFN-γ production from peripheral blood mononuclear cells (PBMCs) obtained from cats experimentally infected with an FIPV isolate that did not develop the disease was significantly increased by heat-inactivated FIPV stimulation in comparison with medium alone. Especially, CD8(+)fIFN-γ(+) cells, but not CD4(+)fIFN-γ(+) cells, were increased. In contrast, fIFN-γ production from PBMCs isolated from cats that had developed FIP and specific pathogen-free (SPF) cats was not increased by heat-inactivated FIPV stimulation. These results suggest that cellular immunity plays an important role in preventing the development of FIP. Measurement of fIFN-γ production with the anti-fIFN-γ MAbs created in this study appeared to be useful in evaluating cellular immunity in cats. 相似文献
35.
Riparian forests greatly influence aquatic ecosystems by providing shade cover, which controls water temperature and limits
primary production. We examined the relationship between forest cover and summer stream temperature in northernmost Japan.
Heat budget and statistical analyses were employed and the results were compared. Heat budget analysis revealed that the water
temperature would decrease almost linearly from 29°C to 25°C with an increase in forested reaches along a 3.2 km stretch of
the river. Multiple regression analysis by the stepwise method chose only open channel length as a variable to explain the
variation in maximum stream temperature. A sharp increase in stream temperature was noted when riparian forest cover was removed
in short lengths, of up to 1.0km; this increasing trend gradually flattened as the length of open stretch increased. Thus,
even small openings in the riparian canopy resulted in drastic rises in summer stream temperature. The maximum summer temperatures
estimated by the two methods were coincided, and can therefore be accurately estimated by regression analysis. Retrospective
analysis based on the regression equation showed that the maximum summer temperature in 1947 was 6°C lower than at present,
and that a sharp increase occurred from 1947 to 1960, a period of rapid expansion of agricultural land development in the
watershed. 相似文献
36.
T. Ona T. Sonoda K. Ito M. Shibata Y. Tamai Y. Kojima J. Ohshima S. Yokota N. Yoshizawa 《Wood Science and Technology》2001,35(3):229-243
Relationships between cell and pulp properties were investigated by examining the within-tree property variations in Eucalyptus camaldulensis and Eucalyptus globulus. Properties investigated included proportions of ray and axial parenchyma, thickness of cell walls and cell wall percentages.
The characteristics of the ray and axial parenchyma (their proportions and wall thickness) were found to have a significant
influence on all measured pulp properties, including paper strength properties. Multiple regression of pulp properties in
relation to cell properties revealed that nearly all measured pulp properties were explained by cell properties at the 1%
significance level. It was concluded, therefore, that all cell types are important for predicting pulp properties, and it
is strongly recommended that tree breeding programs for Eucalyptus include the measurement of all cell types.
Received 6 July 1999 相似文献
37.
The effects of shoot size and differences in budburst phenology ofQuercus serrata trees on the spatial patterns of galls were investigated for two cynipid species: the sexual generation ofAndricus moriokae and the agamic generation ofAphelonyx glanduliferae. There were marked differences in budburst phenology, but these did not affect the gall density on the tree. The galls of
both cynipids showed a contagious distribution in their respective trees, but different abundance patterns under high gall
density. The mean number of galls ofA. glanduliferae over a shoot size range was positively correlated with shoot size. More galls ofA. moriokae appeared on larger shoots on trees on which many buds had started growing before oviposition by the agamic adults. In the
case of a tree on which a few buds had burst by the time of oviposition, the mean numbers ofA. moriokae galls on shoots of particular size ranges depended on the frequency of shoots in the size class. These results suggest that,
although these cynipids prefer to attack larger shoots within a host tree, they may exhibit plasticity in their preference
in response to changes in budburst phenology of the host plant relative to the time of oviposition. 相似文献
38.
39.
Tetsuji Ota Tsuyoshi Kajisa Nobuya Mizoue Shigejiro Yoshida Gen Takao Yasumasa Hirata Naoyuki Furuya Takio Sano Raul Ponce-Hernandez Oumer S. Ahmed Heng Sokh Vuthy Ma Eriko Ito Jumpei Toriyama Yukako Monda Hideki Saito Yoshiyuki Kiyono Sophal Chann Nang Ket 《Journal of Forest Research》2015,20(6):484-492
40.