Diversity and zonal distribution of arbuscular mycorrhizal fungi on the northern slopes of the Tianshan Mountains     

Shi ZhaoYong  Chen ZhiChao  Zhang LiYun  Feng Gu  Christie Peter  Tian ChangYan  Li XiaoLin 《中国科学D辑(英文版)》2007,50(1):135-141

The arbuscular mycorrhizal (AM) fungal status of the 20 most common plant species distributed in 4 vegetation types (meadow steppe, desert steppe, steppe desert and typical desert) on the northern slopes of the Tianshan Mountains was investigated. Samples of the plant species and their rhizosphere soils were collected from the 4 vegetation zones and examined to compare their mycorrhizal status, AM fungal spore densities, biovolumes, and community structures. 28 AM fungal species were isolated from the rhizosphere soils: of these, 5 belonged to Acaulospora, 1 to Archaeospora and 22 to Glomus. 5 AM fungi, Glomus aggregatum, G. claroideum, G. deserticola, G. etunicatum and G. sinuosum, were observed in all 4 zonal types. No significant differences were observed in mean proportion of root length colonized by AM fungi among the plant species within each zonal type. Comparing the 4 zonal types, Plantago minuta (84.5%) in steppe desert and Eremopyrum orientale (83.1%) in typical desert showed the highest root colonizatsion rates. AM fungal spore densities and biovolumes were significantly different in the different zonal types. AM fungal spore densities and biovolumes, species richness and diversity were highest in meadow steppe and lowest in typical desert.  相似文献   

Uniform asymptotic Green's functions for efficient modeling of cracks in elastic layers with relative shear deformation controlled by linear springs     

Anthony P. Peirce  Hongren Gu  Eduard Siebrits 《国际地质力学数值与分析法杂志》2009,33(3):285-308

We present a uniform asymptotic solution (UAS) for a displacement discontinuity (DD) that lies within the middle layer of a three‐layer elastic medium in which relative shear deformation between parallel interfaces is controlled by linear springs. The DD is assumed to be normal to the two interfaces between the elastic media. Using the Fourier transform method we construct a leading term in the asymptotic expansion for the spectral coefficient functions for a DD in a three‐layer‐spring medium. Although a closed‐form solution will require a solution in terms of an infinite series, we demonstrate how this UAS can be used to construct highly efficient and accurate solutions even in the case in which the DD actually touches the interface. We compare the results using the Green's function UAS solution for a crack crossing a soft interface with results obtained using a multi‐layer boundary element method. We also present results from an implementation of the UAS Green's function approach in a pseudo‐3D hydraulic fracturing simulator to analyze the effect of interface shear deformation on the fracture propagation process. These results are compared with field measurements. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

用固体潮观测资料将钻孔应变变化换算为地层的应力变化   总被引：1，自引：1，他引：0  

骆鸣津  顾梦林  杨毅 《大地测量与地球动力学》2000,20(1):73-78

利用钻孔应变观测值中潮汐频段部分和钻孔岩芯的弹性系数,将钻孔应变换算为地层应力的格值,用此格值可将钻孔应变的非潮汐变化换算成该地地层的非潮汐应力变化.从潮汐模型研究和潮汐观测结果来看,勒夫数受地球大结构的影响,空间变化不大,据此可用勒夫数的模型值去求定标定应力.由钻孔应变观测值求定钻孔应变的面应力系数和差应力系数,而不必知道耦合介质的力学性能.探头周围介质若非各向同性时,应力系数可用椭圆的解析式拟合.此外,还讨论了同井、同台、台网的校核问题,以及应力场模型的拟合和漂移的分离问题.  相似文献   

黑宝山膨润土的物化性能和应用试验研究     

季金华  张书亮  顾志峰 《江苏国土资源》2000,25(1)

对黑宝山膨润土的化学成分、阳离子交换量、吸蓝量、胶质价、膨胀容、比表面、造浆率、湿压强度和脱色力进行了测定,利用组合样进行了工业活化试验和铸造用土工业试验研究.  相似文献   

Les anneaux de saturne en 1969. Etude morphologique et photométrique. I. Obtention et dépouillement des photographies     

P. Guérin 《Icarus》1973,19(2):202-211

Some excellent photographs of Saturn in yellow and violet light have been taken in 1969 with the 105cm reflecting telescope of the Pic du Midi Observatory. They revealed the existence, inside the C-ring, of an extremely faint, fourth Ring. The reduction of microphotometric tracings along the great-axis of the Rings, have given the photometric curves of the rings in the two colours above. These two curves are very similar. They do not agree with some of the details drawn before and show some new ones.  相似文献   

Isotopic variations in precipitation at Bangkok and their climatological significance     

Yuanqing He  Hongxi Pang  W. H. Theakstone  Zhonglin Zhang  Aigang Lu  Juan Gu 《水文研究》2006,20(13):2873-2884

The stable isotopic composition of precipitation from low to mid latitudes contains information about changes of some climatic factors, such as temperature, precipitation and atmospheric circulation patterns. However, the isotopic variations in the area are very complicated because of the combined influences of these factors. Proper interpretation of the patterns of isotopic variations for palaeoclimate reconstructions in this area requires a detailed understanding of these complex stable isotope controls. The isotopic data (δ¹⁸O and δ²D) in precipitation at the International Atomic Energy Agency–World Meteorological Organization Bangkok station were collected and analysed because of the relatively long and unbroken isotopic records and the particular geographical location. The isotopic variations at Bangkok have strong seasonal patterns owing to distinct source regions in different seasons. In summer, the remote sources of water there can influence the δ¹⁸O values significantly, which is verified by the simple Rayleigh model. In winter, the mixing of isotopically distinct air masses with different origins, i.e. the continental and oceanic air masses, accounts for the isotopic variations. In the transition periods of the Asia–Australia monsoon, namely in May and October, the local vapour contribution may play a role in the isotopic ratios. On the interannual time‐scale, the influences of El Niño–southern oscillation (ENSO) and the Indian Ocean dipole (IOD) on isotopic composition are examined. The indications are that both the ENSO and IOD indices have a significant correlation with the δ¹⁸O ratios, and that the δ¹⁸O ratio in summer rains is significantly more enriched (depleted) during the warm (cold) phase of ENSO/IOD events. All the results suggest that it is useful for us in understanding the water cycling process and may be helpful in palaeoclimate reconstruction in this monsoon region. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Stellar and gaseous velocity dispersions in type II AGNs at 0.3 < z < 0.83 from the Sloan Digital Sky Survey     

W. Bian  Q. Gu †  Y. Zhao  L. Chao  Q. Cui 《Monthly notices of the Royal Astronomical Society》2006,372(2):876-884

  相似文献   

���ڸ���������ϺͶ�������ƫ����     

张磊  顾勇为  归庆明  马朝忠 《大地测量与地球动力学》2007,27(2):99-102

???????????????????????????????????Gauss??Markov ????????????μ??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????Σ?????????????????????????????????????????????????????  相似文献   

用相似释用方法制作小麦生育期逐旬气候预测     

史印山  顾光芹 《气象科技》2013,41(2):389-393

利用气候模式产品、NCEP/NCAR再分析500 hPa旬平均高度资料和河北省冬小麦种植区各测站的逐句降水、气温资料.运用相似释用技术,研制了冬小麦返青—拔节、拔节—抽穗、抽穗—乳熟、乳熟—成熟4个生育期间逐旬气温、降水预测方法,建立了冬小麦各生育期干旱指标预测模型,并在预测业务中应用.预测检验结果表明,用模式产品解释应用方法制作逐旬气候预测是可行的.  相似文献   

河南省短时强降水及其云团特征分析   总被引：3，自引：0，他引：3  

谷秀杰 《气象与环境科学》2013,36(1):15-20

根据河南省119个气象站1991-2010年5-9月逐时降水量资料,利用线性趋势和克里金插值等方法,分析了河南省短时强降水及其云团的特征.结果表明:河南省短时强降水自西向东、自北向南呈递增趋势,20.0 ～49.9 mm/h级别的降水在驻马店地区东部和信阳地区西部有明显增多趋势;≥50.0 mm/h级别的降水在周口地区北部有一高值中心.年际变化表明,20.0～49.9 mm/h级别的降水呈显著增加趋势,而≥50.0 mm/h级别的降水呈略增加趋势,但是不显著.月份间的差异非常明显,7月份出现的频次最多,其次是8月份,再次是6月份,5月份和9月份最少.日变化统计表明,上午最少,午后逐渐增加,傍晚和凌晨最多.历年极值雨量7月份出现次数最多,并集中分布在河南省中东部地区,西部地区极值雨量不超过50.0 mm/h,明显低于中东部地区.影响河南省短时强降水的对流云团大致有3个源地6条路径,云团特征可分三种类型,分别为不规则对流云团、圆形或椭圆形云团、带状云系.当有强降水发生时,Tbb值一般很低,但是Tbb值的大小与小时雨量没有很好的相关性.  相似文献