长江春季禁渔对崇明北滩渔业群落的影响   总被引：4，自引：0，他引：4  

刘凯  张敏莹  徐东坡  段金荣  施炜纲 《中国水产科学》2006,13(5):834-840

对1999至2005年每年的4～6月间崇明北滩渔业群落进行研究,对春季禁渔前后相关指标进行对比分析.实施长江春季禁渔前,崇明北滩渔业群落组成为11目、19科、25属、27种.实施长江春季禁渔后,该群落共出现鱼虾蟹等渔业生物30种,分别隶属于9目18科26属.群落优势种为凤鲚[Coilia mystus(Linnaeus)]、棘头梅童鱼[Collichthys lucidus(Richardson)]、红狼牙(鱼 )虎[Odontamblyopus rubicundus(Hamilton-Bnchanan)]和狭颚绒螯蟹[Eriochier leptognathus (Rathbun)],单位质量小于20g的小型种类占绝对优势,鱼类幼体所占比例极大.多样性特征值平均指标为:Margalef指数1.50,Wilhm改进指数1.83,Simpson指数0.24,Pielou指数0.72.实施春季禁渔后该群落组成变化显著,复杂程度有所下降,多样性特征值仍大幅度波动,企稳回升趋势不明显.结果显示,春季禁渔对该群落的保护作用尚不明显,针对该群落的保护工作应进一步加强.  相似文献   

Modelling uptake of Na and Cl by tomato in closed-cycle cultivation systems as influenced by irrigation water salinity     

H. Varlagas  G. Mouzakis  I. Karapanos 《Agricultural Water Management》2010,97(9):1242-155

The aim of the present investigation was to simulate the uptake concentrations (weights of ion per volume of water absorbed) of Na⁺ and Cl⁻ in hydroponic tomato crops as a function of the NaCl concentration in the root zone. An empirical model was calibrated and validated, which can be incorporated into on-line operating decision support systems aimed at optimizing the nutrient supply and minimizing the discharge of drainage solution in tomato crops grown in closed-cycle hydroponic systems. Three experiments were conducted, of which one was carried out to calibrate the model using irrigation water with NaCl concentration ranging from 0 to 14.7 mol m⁻³ while the other two experiments were commissioned to validate the model within either a low (0.5-2 mol m⁻³) or a high (1.2-12 mol m⁻³) concentration range. The model could successfully predict the uptake concentration of Na⁺, but Cl⁻ could not be simulated by this model at external Cl⁻ concentrations lower than 10 mol m⁻³. The results indicate that Na⁺ is excluded actively and effectively by the tested tomato cultivar even at low external Na⁺ concentrations, while Cl⁻ is readily taken up at low concentrations, particularly during the initial growing stages. Due to the efficient exclusion of Na⁺ by tomato, the Na⁺ concentration in the root environment increased rapidly to extremely high levels even when the Na⁺ concentration in the irrigation water was relatively low. These results indicate that tomato genotypes characterized by high salt-exclusion efficiency, require irrigation water with a very low NaCl concentration, if they are grown in closed hydroponic systems and the drainage water is not flushed periodically. To maintain Na⁺ at levels lower than 19 mol m⁻³ in the root zone of the tomato hybrid ‘Formula’ in closed hydroponics, a maximum acceptable Na⁺ concentration of 0.53 mol m⁻³ was estimated for the irrigation water.  相似文献   

使用BASIC语言计算大界闭合差     

张肇裕  崔崇龙 《森林工程》1999,15(3):41-42

本文介绍了笔者编制的一套用于求算闭合差的程序,该程序功能强大,计算速度快,用学习机即可使用。适合森林调查的外业使用。  相似文献   

内蒙古牧区夏季肉羊圈舍环境参数测定及其对肉羊育肥和生理指标影响     

崔绪奎  王金文  康俊浩  孟宪锋  胡志成  吴宏军  任少广 《山东农业科学》2015,(7)

为研究探讨夏季牧区肉羊圈舍内环境参数变化对肉羊育肥效果及生理指标的影响,笔者自2014年7月27日始,在内蒙古海拉尔市谢尔塔拉农牧场种羊场,对封闭式轻钢结构羊舍内外环境参数及肉羊生理指标和育肥效果进行测定。结果表明:在自然通风换气条件下,舍内平均温度比舍外环境高3.0℃。高温时段为每日14∶00,舍内温度达到33.3±4.4℃,比环境温度高5.6℃。低温时段在凌晨2∶00,舍内温度比环境温度高3.6℃。舍内温度及湿度变化趋势与舍外环境温度、湿度变化相同。舍内空气中CO2平均含量1 086±204 mg/m3,NH3及H2S未检测出,空气质量达到T388要求。夏季舍内温、湿度变化对育肥肉羊体温、脉搏等生理指标没有影响,但呼吸次数有所增加。育肥羊平均日增重207 g,料重比5.85∶1,扣除饲草料费用,每只肉羊期内增重平均收入63.5元。  相似文献   

砖混结构密闭式鸡舍的应用研究     

许建中  吴明华 《安徽农业科学》1995,23(2):176-179

本试验对砖混结构密闭式鸡舍内的环境参数与蛋鸡生产性能间的关系进行了探讨。结果表明，该类鸡舍的隔热性能不够理想，高温季节舍内环境参数随外界变化较明显。在现有条件下，提高鸡舍的保温隔热性能，改进通风降温设施，可提高砖混结构密闭式鸡舍的应用效果。  相似文献   

“闭路开环”原理在西部生态经济建设中的应用     

周升起  姜学民 《中国生态农业学报》2005,13(2):22-24

阐述了“闭路开环”原理内涵及其基本内容,分析了“闭路开环”原理在西部生态经济建设中的政策含义(包括投入政策、激励约束政策和人才政策)与实践意义,并针对西部生态经济建设模式、生态产业、园区生态经济和生态经济制度建设等提出具体策略  相似文献   

Application of a quantum cascade laser-based spectrometer in a closed chamber system for real-time δC and δO measurements of soil-respired CO₂     

Adrian Kammer  Béla Tuzson  Joachim Mohn 《Agricultural and Forest Meteorology》2011,151(1):39-48

Laser spectroscopy is an emerging technique to analyze the stable isotopic composition of soil-respired CO₂ (δ¹³C_resp, δ¹⁸O_resp) in situ and at high temporal resolution. Here we present the first application of a quantum cascade laser-based spectrometer (QCLS) in a closed soil-chamber system to determine simultaneously δ¹³C_resp and δ¹⁸O_resp. In a Swiss beech forest, a total of 90 chamber measurements with 20 min sampling time each were performed. The instrument measured the δ¹³C and δ¹⁸O of the CO₂ in the chamber headspace at every second with a precision of 0.25‰, resulting in Keeling plots with 1200 data points. In addition, we calculated δ¹³C_resp directly from the flux ratio of ¹³CO₂ and ¹²CO₂. The flux-ratio values were 0.8‰ lower than the Keeling plot intercepts when the flux rates were derived from quadratic curve fits of the CO₂ increase. The δ¹⁸O-Keeling plots showed a significant bending very likely due to the equilibration of chamber CO₂ with the ¹⁸O of surface soil water. Therefore, we used a quadratic curve fit of the Keeling plots to estimate δ¹⁸O_resp. Our results also revealed that δ¹³C_resp was not constant throughout the CO₂ accumulation in the closed soil chambers: there were significant but non-systematic variations in δ¹³C_resp for the first 10 min, and systematic shifts in δ¹³C_resp of on average 1.9 ‰ in the second part of the 20-min measurements. These biases were probably caused by non-steady-state conditions in the soil-chamber system. Our study illustrates that the high temporal resolution of QCLS measurements allows the detection of non-linearities in the isotopic effluxes of CO₂ from the soil due to soil-chamber feedbacks. This information can be used to improve the estimates for δ¹³C_resp and δ¹⁸O_resp.  相似文献   

Transmission of some species of internal parasites in horses born in 1993, 1994, and 1995 on the same pasture on a farm in central Kentucky     

E.T. Lyons  S.C. Tolliver  S.S. Collins  J.H. Drudge  D.E. Granstrom 《Veterinary parasitology》1997,70(4):9-240

Data are presented on the last 3 years of a 7-year study (1989–1995) on transmission of natural infections of internal parasites in horse foals (n = 27) born in 1993, 1994, and 1995 on the same pasture on a farm in central Kentucky. The foals were in a closed breeding herd of horses. Research on the first 4 years (1989–1992) of the study was published earlier (Lyons et al., 1991, 1994). Thirty-five species of endoparasites were identified, including 24 species of small strongyles. Monthly, seasonal, and host-age transmission patterns were elucidated for the parasites. Comparison of data between the first 4 years and last 3 years of the study indicates similarities, but also differences, including an increase in prevalence and numbers of Thelazia lacrymalis and Anoplocephala perfoliata.  相似文献   

绿色农产品封闭供应链风险评估研究     

王雪峰 《安徽农业科学》2011,39(26):16318-16320

在现有供应链风险和农产品供应链文献研究的基础上,对绿色农产品封闭供应链中涉及生产、经营和消费等环节的相关节点主体进行实际调研分析,将供应链系统中的主要风险要素归纳为环境风险、系统风险、信息风险、管理风险和质量安全风险5类。运用模糊综合评价方法对绿色农产品封闭供应链风险进行评价,得到绿色农产品封闭供应链风险的模糊综合评价分值,结果表明绿色农产品封闭供应链风险等级属于中等,具有较高的风险,这与当前实际情况基本相符。从各级指标权重也可看出,影响风险的关键一级指标是系统风险、信息风险和质量安全风险,影响风险的关键二级指标是核心企业协调控制能力、信息追溯技术的实现程度、质量安全体系建设水平等。因此,应该着重从这些方面采取防范和控制措施来降低绿色农产品封闭供应链风险。  相似文献   

Structure of thermal convection development based on inhomogeneous water surface cooling   总被引：1，自引：1，他引：0  

Kunihiko Hamagami  Ken Mori  Yasumaru Hirai 《Paddy and Water Environment》2008,6(4):373-380

The generation and development of thermal convection based on inhomogeneous water surface cooling were examined by hydraulic and numerical experiments to examine the characteristics of thermal convection in a closed water body with aquatic plants. A visualization experiment revealed the structural characteristics of a whirlpool when thermal convection was generated quantitatively by using PIV analysis. Then, a water temperature measurement experiment demonstrated that a steady cold water mass generated based on the heat flux transport from the water surface increases. This explained each of the three stages in the convection development process. Moreover, aquatic plants, which grow thickly on the water surface, cause not only vertical but also horizontal flows based on the density difference with the water surface that is not covered by plants, and thus change the development process of the convection cell.  相似文献