Substrate selection and seasonal variation in abundance and size composition of isopod Lirceus fontinalis in Ontario streams, Canada     

ZHAO Xiaoxia Michael G FOX David C. LASENBY Alexis C. ARMIT Dolly N. KOTHAWALA 《中国海洋湖沼学报》2007,25(2):215-220

The abundance and size composition of stream isopods Lirceus fontinalis were investigated from April 2001 to August 2002 in 3 streams in southern Ontario, Canada. Effects of current speed was released from the analysis by choosing slow flowing water. The effects of substrate, season and water depth on the abundance, distribution and size composition of the isopods were analyzed. It was found that substrate and season influence isopods the most. The rocky substrate with attached filamentous macro-algae contains an isopod abundance 7.05 times that of bare rock substrate and 14.6 times that of fine-sand and mud substrate. There was a large variation with respect to seasonality in both abundance and size composition of the isopods, with the highest abundance occurring in summer and the lowest in winter and spring; individual isopods also tend to be larger in the winter and spring. In all substrates, shallow areas tend to support higher densities of isopods than deeper areas.  相似文献   

Coupled surface water–groundwater model and its application in the arid Shiyang River basin,China     

Li‐Tang Hu  Zhong‐Jing Wang  Wei Tian  Jian‐Shi Zhao 《水文研究》2009,23(14):2033-2044

The planning and management of water resources in the Shiyang River basin, China require a tool for assessing the impact of groundwater and stream use on water supply reliabilities and improving many environment‐related problems such as soil desertification induced by recent water‐related human activities. A coupled model, integrating rule‐based lumped surface water model and distributed three‐dimensional groundwater flow model, has been established to investigate surface water and groundwater management scenarios that may be designed to restore the deteriorated ecological environment of the downstream portion of the Shiyang River basin. More than 66% of the water level among 24 observation wells have simulation error less than 1·0 m. The overall trend of the temporal changes of simulated and observed surface runoff at the Caiqi gauging station remains almost the same. The calibration was considered satisfactory. Initial frameworks for water allocation, including agricultural water‐saving projects, water diversion within the basin and inter‐basin water transfer, reducing agricultural irrigation area and surface water use instead of groundwater exploitation at the downstream were figured out that would provide a rational use of water resources throughout the whole basin. Sixteen scenarios were modelled to find out the most appropriate management strategies. The results showed that in the two selected management options, the groundwater budget at the Minqin basin was about 1·4 × 10⁸ m³/a and the ecological environment would be improved significantly, but the deficit existed at the Wuwei basin and the number was about 0·8 × 10⁸ m³/a. Water demand for domestic, industry and urban green area would be met in the next 30 years, but the water shortage for meeting the demand of agricultural water use in the Shiyang River basin was about 2·2 × 10⁸ m³/a. It is suggested that more inter‐basin water transfer should be required to obtain sustainable water resource use in the Shiyang River basin. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

不同植被盖度沙质草地生长季土壤水分动态   总被引：1，自引：1，他引：1  

王明明  刘新平  李玉霖  车力木格  罗永清  孙珊珊  魏静 《中国沙漠》2019,39(5):54-61

水分是干旱半干旱沙地生态系统最大的限制因子，研究植被盖度和土壤水分之间的关系有助于沙地生态恢复和保护。基于生长季科尔沁沙质草地不同植被盖度下土壤水分动态和降水的观测试验，分析了沙质草地植被盖度和土壤水分的耦合关系。结果表明：在土壤剖面上土壤水分存在明显的分层结构，依次为水分剧变层（0~40 cm）、缓变层（40~100 cm）和稳定层（100~180 cm）；植被盖度对土壤水分有很大影响，不同植被盖度下土壤含水量存在显著差异，土壤水分与盖度之间呈倒“V”型关系，土壤水分状况在28%的盖度下最优；不同的植被盖度下土壤水分对降水的响应也存在差异，在13%盖度下响应最敏感，28%和46%的盖度下响应微弱，后二者的土壤水分也相对稳定。在沙地生态恢复建设过程中合理的植被盖度配置可提高降水利用效率，并能使土壤水分和植被达到一种良好的平衡状态，从而有利于生态系统的稳定。  相似文献   

关于城镇基准地价更新的思考     

赵建勋  贾建秋 《山东国土资源》2007,23(12):28-29

1基准地价更新技术途径基准地价更新是在土地定级或划分均质区域的基础上,用土地收益、市场交易的样点地价及地价指数等来重新确定各类用途土地在现状利用条件下于特定基准日的土地使用权平均价格。基准地价定期更新,既保持了基准地价的现势性,又能充分发挥基准地价在土地市场和土地资产管理中的重要作用。基准地价更新要严格按照国土资源部《城镇土地分等定级规程》、《城镇土地估价规程》、《中华人民共和国土地管理法》为主要技术依据,在借鉴国内已有的城市基准地价更新经验的基础上,从该地区实际情况出发,充分利用已有的土地定级估价、…  相似文献   

The fronts of the Huanghai cold water mass (HCWM) induced by tidal mixing   总被引：1，自引：0，他引：1  

Zhao Baoren 《中国海洋湖沼学报》1986,4(2):159-170

Since Simpson and Hunter proposed in 1971 the idea that shallow water fronts were induced by tidal mixing, many authors have investigated the tide induced shallow water fronts in various areas. It was generally assumed that a critical value of the stratified parameterK=log₁₀(H/U ³) may be used to identify the location of these fronts. Here, H means the depth of sea waler. U denotes the characteristic velocity of tidal current. and the critical value ofK is generally laken as 1.8–2.0. In this paper. Simpson-Hunter’s stratified parameterK was calculated by using quasi-maximum current velocity (which consists of the six main tidal constituents. i.e.M ₂.S ₂,O ₁.K ₁.M ₄,MS₄) in the H ranghai Sea (Yellow Sea) and in the northern Donghai Sea (East China Sea) as well. Caleulated results show that the areas of the Subei (the northern part of Jiangsu) Shoal. the area off the mouth area of the Changjiang (the Yangtze) River, along the coast of Shandong Peninsula. and along the western coast of Korea, the tidal mixing is strong. Calculations also show that along the whole boundary of the HCWM and also along the western boundary of the cyclonic eddy in the northern Donghai Sea, i.e. along the fronts, the value ofK is found to be very close to the eritical value 1.8. It is also to be noied that at these locations, the temperature of the surface water is very low. These clearly show that shallow water fronts in the Huanghai Sea and in the northern Donghai Sea as well, are induced by tidal mixing. Contribution No. 1241 from Institute of Oceanology, Academia Sinica. This paper was published in Chinese in theOcean. et Limn. Sinica 16(6): 451–459, 1985.  相似文献   

二道沟金矿床中黄铁矿晶体形态及热电性与金矿化的关系     

赵秀英 《国土资源》1990,(4)

已有文献认为:空穴型黄铁矿的存在对金成矿有利。作者对二道沟金矿床的研究表明,金矿化程度不仅与黄铁矿的热电性有关,而且与黄铁矿的晶体形态关系十分密切。富矿体中黄铁矿晶体形态复杂,种类多并以五角十二面体为主,叶夫济科娃晶体形态得分值(XFeS_)高;含矿较贫或不含矿的岩体黄铁矿晶体形态简单,种类少并以立方体为主,叶夫济科娃晶体形态得分值(XFeS_2)低。  相似文献   

Nodes and Field of Tourist Origins to Ancient Village——A Case Study of Huangcheng Village in Shanxi Province of China     

ZHONG Jing  ZHANG Jie  LI Donghe    ZHAO Yong  LU Song    SHI Chunyun 《中国地理科学(英文版)》2007,17(3):280-287

Based on Hagget's theory of spatial structure,researches on the nodes and field of tourist origins to Huang-cheng Village in Shanxi Province of China have been explored.Nodal hierarchy structure of tourist origins is analyzed with cluster analysis and the gravity model.And field of tourist origins is analyzed with attraction radius index(R)and geography concentration index(G).In the field analysis,R and G of Huangcheng Village are compared with Xidi Village that is a world heritage located in Huangshan City of Anhui Province in China.According to comparison of loca-tions of two areas,influential factors for field area of Huangcheng Village are identified.It is concluded that:1)cluster analysis and gravity model can be complementary methods to each other for nodal hierarchy structure analysis of tour-ist origins;and 2)as far as location is concerned,the weak intensity effect of tourism resources in the tourist region is a major cause for explaining why tourist origins to Huangcheng Village are mainly its neighboring areas.Moreover,it is suggested that the regional effect of tourist resources should be regarded as a component of destination attractiveness when applying gravity model.  相似文献   

EGM96和EGM2008地球重力场模型计算弹道扰动引力的比较   总被引：2，自引：2，他引：0  

刘晓刚  吴晓平  赵东明  吴星 《大地测量与地球动力学》2009,29(5)

给出了利用地球重力场模型计算扰动引力以及重力场模型截断误差的公式,计算了36阶、360阶、2 160阶地球重力场模型在径向和水平方向的截断误差,并对36阶、360阶的EGM96和EGM2008重力场模型计算的弹道扰动引力矢量进行了分析和比较.结果表明,采用重力场模型计算扰动引力时,模型阶数和弹道点的高度越低,模型截断误差越大;EGM96和EGM2008模型的一致性随着模型阶数的升高而逐渐降低.总体来看,EGM2008模型的精度要好于EGM96模型.  相似文献   

Cr^3＋在改善三元复合驱中的作用实验研究     

任艳滨  卢祥国  赵兰兰  张运来 《海洋地质译丛》2008,(4):50-54

在三元复合驱矿场应用实践中,由于三元复合体系自身流度控制能力的局限性,必须通过聚合物凝胶前置段塞来改善吸液剖面,这就涉及到聚合物凝胶与三元复合体系的配伍性。通过向三元复合体系中加入有机铬,考察Cr^3＋对三元复合体系黏度、界面张力和阻力系数等性能影响,进而对Cr^3＋聚合物凝胶与三元复合体系配伍性以及Cr^3＋在改善三元复合体系性能方面的作用做出评价。结果表明,Cr^3＋的加入对三元复合体系黏度和界面张力影响不大,但阻力系数和残余阻力系数却明显增加。当采用Cr^3＋聚合物凝胶作为前置段塞或采用添加Cr^3＋的三元复合体系进行复合驱油实验时,其采收率增加幅度都要高于普通三元复合驱。这不仅显示出Cr^3＋聚合物凝胶与三元复合体系间良好的配伍性,而且为改善三元复合驱增油效果提供了新的途径。  相似文献   

Synthesis,algal inhibition activities and QSAR studies of novel gramine compounds containing ester functional groups     

李霞  于良民  姜晓辉  夏树伟  赵海洲 《中国海洋湖沼学报》2009,27(2):309-316

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