近百年中国北部南温带北界界限的动态变化

<正> 1.前言在研究气候冷暖变化时,气候学家所采用的指标主要有年平均气温、最冷(暖)月平均气温、气温距平、寒冷指数等;在研究农业气候的热量变化时,所采用指标集中在≥0℃或≥10℃积温上。本文则从农业气候的角度出发,采用农业气候带分界的热量指标,来研究近百年我国北部南温带北界界限的动态变化。采用农业气候带分界指标不仅可以反映出气候的冷暖变化,而且有一定的农业意义。     

甘肃省民勤治沙综合试验站区域生态经济型优化模式的设计

以甘肃省民勤治沙综合试验站区域为系统，应用线性规划的方法，建立区域生态经济型系统的优化模式。结果表明，区域系统在现有的生产条件及生产力水平下，要达到最大经济效益，并保证区域系统的生态趋于良性特环 ，其农林牧三业用最优比例为１：９．５：９．５，此时区域系统的经济纯收入最大，为１１３．７２万元，年人均纯收入达５６８６元。     

黑松针叶提取物抗霉菌活性的研究

采用滤纸片法,检测不同质量浓度的针叶提取物对霉菌的抑制圈大小,以研究黑松针叶提取物的抗霉菌活性。结果表明:黑松针叶提取物具有抗霉菌活性,但抑制效果与其质量浓度不成正比;3种提取物中,乙醇提取物的抗霉菌效果最显著,丙酮和水提取物的抗霉菌效果次之。其对黑曲霉、青霉、根霉起最佳抑制效果的质量浓度分别为6.25、25.01、2.5 g/L,其抑菌圈直径分别为14.8、16.61、2.6 mm。     

Comparison of structural diversity of tree-crop associations in Peripheral and Buffer zones of Gachabari Sal forest area, Bangladesh

The structural diversity of different tree-crop associations were studied at Gachabari Sal forest area of Madhupur Garh on Buffer and Peripheral Zone during 2006. The total density, basal area of trees in the Buffer and Peripheral Zone were 155.5 trees·hm^-2, 795.4 trees·hm^-2 and 3.9 m^2·hm^-2, 5.8 m^2·hm^-2, respectively. No regeneration and natural trees were found in Peripheral Zone and the Zone is totally occupied by exotic species where the Buffer Zone comprised of both natural and exotic trees. The Peripheral Zone belonged to younger and smaller trees whereas the Buffer Zone belonged to mixture of smaller, taller, younger and mature trees simultaneously. For the practicing of different agroforestry systems both Zones have lost their original characters of Sal forest.     

百里杜鹃林区采煤塌陷前后土壤养分状况对比研究

【目的】揭示采煤塌陷对贵州百里杜鹃林区土壤养分的影响。[方法】在选取典型对比样地的基础上,对百里杜鹃林区不同层次土壤进行了分层对比分析。【结果]结果表明,采煤塌陷后,百里杜鹃林区土壤酸性减弱,向中性趋近;土壤有机质含量有降低的趋势;土壤全量养分（全氮、全磷、全钾）含量有所提高;有效氮（铵态氮、硝态氮）含量总体提高,但速效磷、速效钾含量明显降低。[结论]采煤塌陷打破了百里杜鹃林区土壤养分的平衡,尤其是减少了有效磷、有效钾的供应。     

Growth overfishing in the brown shrimp fishery of Texas, Louisiana, and adjoining Gulf of Mexico EEZ

Growth overfishing in the brown shrimp, Farfantepenaeus aztecus, fishery in inshore (estuarine) and offshore (Gulf of Mexico) territorial waters of Texas and Louisiana, and adjoining waters of the United States’ (U.S.) Exclusive Economic Zone (EEZ), and its potentially detrimental economic consequences to the harvesting sector, have not been among major concerns of Federal and State shrimp management agencies. Three possible reasons include (1) environmentally influenced variations in recruitment that cause wide fluctuations in annual landings, which tend to obscure effects of fishing, (2) competition between inshore and offshore components of the harvesting sector, and (3) partitioning of management jurisdiction among a Federal council and two State agencies. Wide variations in landings led to beliefs that high levels of fishing mortality were tolerable and recruitment overfishing was of no major concern. This encouraged somewhat laissez-faire management approaches that allowed fishing effort to increase over the years.Our objectives were to determine whether growth overfishing occurred in this fishery during 1960–2006, and whether and how decreases in size of shrimp within the landings, in response to increases in fishing effort, affected inflation-adjusted annual (calendar year) ex-vessel value of the landings, i.e., their value to the harvesting sector. Growth overfishing occurred in the early 1990s, and then abated as fishing effort declined due to rising fuel costs and competition from imported shrimp. However, inflation-adjusted annual ex-vessel value of the landings peaked in 1985, prior to growth overfishing.Management actions implemented in 2001 for Texas’ territorial waters, and in the EEZ off Texas and Louisiana in 2006, should limit future fleet expansion and increases in fishing effort, thereby reducing the chances of growth overfishing and its potentially detrimental economic impacts on the harvesting sector. Growth overfishing should be included among the guidelines for future management of this brown shrimp fishery.     

中原经济区建设中农村人口有序转移的政府责任研究

以当前国家主体功能区划分背景下中原经济区建设为背景,在对中原经济区建设中农村人口有序转移进行研究的基础上,提出了各级政府部门推动农村人口有序转移的对策建议。     

准噶尔南缘扇缘带种植业结构分析

通过对准噶尔南缘扇缘带种植业生产的分析及试验研究，提出了适合本地带农田的经粮结构、草经粮结构、林经草结构和专业化生产４种种植业结构类型。根据经济效益、生态效益和社会效益综合评定，认为采用草粮或林经草种植业结构类型，同时贯彻以牧为主、农牧结合的方针是本地带开发利用的最佳途径     

三峡库区库岸带开发中旅游业的发展模式及其对策

三峡库区库岸带人口密集,人地矛盾十分紧张,工业基础遭到破坏,单纯发展一、二产业,投入比较大,且生态效益得不到保障.本文针对三峡库区库岸带发展的现状和存在的问题,提出了库岸带旅游业的发展模式和对策.     

Comparison of modeling approaches to quantify residue architecture effects on soil temperature and water

RZ-SHAW is a hybrid model, comprised of modules from the Simultaneous Heat and Water (SHAW) model integrated into the Root Zone Water Quality Model (RZWQM) that allows more detailed simulation of different residue types and architectures that affect heat and water transfer at the soil surface. RZ-SHAW allows different methods of surface energy flux evaluation to be used: (1) the SHAW module, where evapotranspiration (ET) and soil heat flux are computed in concert with a detailed surface energy balance; (2) the Shuttleworth–Wallace (S–W) module for ET in which soil surface temperature is assumed equal air temperature; and (3) the PENFLUX module, which uses a Penman transformation for a soil slab under incomplete residue cover. The objective of this study was to compare the predictive accuracy of the three RZ-SHAW modules to simulate effects of residue architecture on net radiation, soil temperature, and water dynamics near the soil surface. The model was tested in Akron, Colorado in a wheat residue-covered (both standing and flat) no-till (NT) plot, and a reduced till (RT) plot where wheat residue was incorporated into the soil. Temperature difference between the soil surface and ambient air frequently exceeded 17 °C under RT and NT conditions, invalidating the isothermal assumption employed in the S–W module. The S–W module overestimated net radiation (R_n) by an average of 69 Wm⁻² and underestimated the 3-cm soil temperature (T_s3) by 2.7 °C for the RT plot, attributed to consequences of the isothermal assumption. Both SHAW and PENFLUX modules overestimated midday T_s3 for RT conditions but underestimated T_s3 for NT conditions. Better performances of the SHAW and PENFLUX surface energy evaluations are to be expected as both approaches are more detailed and consider a more discretized domain than the S–W module. PENFLUX simulated net radiation slightly better than the SHAW module for both plots, while T_s3 was simulated the best by SHAW, with a mean bias error of +0.1 °C for NT and +2.7 °C for RT. Simulation results for soil water content in the surface 30 cm (θ_v30) were mixed. The NT conditions were simulated best by SHAW, with mean bias error for θ_v30 within 0.006 m³ m⁻³; RT conditions were simulated best by the PENFLUX module, which was within 0.010 m³ m⁻³.