不同农艺措施组合对云南红壤坡耕地氮素平衡和流失的影响

通过对野外坡度为26．05％的径流小区实地观测，研究种植方式、施肥方式和等高植物篱条带3种农艺措施不同组合对云南红壤坡耕地氮素投入、带走平衡的影响。结果表明，在等高种植＋平衡施肥＋等高植物篱条带组合农艺措施条件下，收获玉米带走的氮为177．24kg·hm^-2，占水土流失和收获玉米带走氮总量的99．42％，水土流失带走1．03kg·hm^-2的氮，占水土流失和收获玉米带走氮总量的0．58％；顺坡种植＋农民习惯施肥收获玉米带走的氮仅为120.31kg·hm^-2，占水土流失和收获玉米带走氮总量的79．36％，而水土流失带走31．29kg·hm^-2的氮，占带走氮总量的20．64％。等高种植比顺坡种植增加收获玉米带走氮素13．36kg·hm^-2，减少水土流失带走氮素18．53kg·hm^-2；等高种植和平衡施肥条件下，等高植物篱条带因占用少量土地而减少收获玉米带走氮素6．09kg·hm^-2，减少水土流失带走氮素5．73kg·hm^-2；顺坡种植和习惯施肥条件下，等高植物篱条带减少收获玉米带走氮素5．39kg·hm^-2，减少水土流失带走氮素29．97kg·hm^-2；平衡施肥比习惯施肥增加收获玉米带走氮素49．66kg·hm^-2，减少水土流失带走氮素6．00kg·hm^-2。云南红壤坡耕地氮素的平衡主要与氮肥、钾肥施用量和玉米籽粒、秸秆产量有密切关系，施氮量高，氮素投入高于带走；平衡施肥玉米籽粒、秸秆产量高，氮带走总量较多，氮素带走略高于投入；习惯施肥玉米籽粒、秸秆产量低，氮素投入高，带走较少。     

作物气孔导度模型研究进展及应用现状

旨在为作物耗水和碳水交换相关研究的模型选择提供理论指导,本研究归纳了气孔导度对单一和综合环境因子的响应情况;对现有气孔导度模型进行了分类和比较,包括基于Jarvis模型建立和改进的经验模型、基于BWB模型建立和改进的半经验模型、基于ABA调控建立和改进的模型、基于保卫细胞膨压控制理论建立和改进的模型;并概述了气孔导度模型在作物水分利用研究领域的应用,以叶片气孔导度和冠层导度的定量关系为切入点建立多尺度联合的机理模型将是未来作物耗水尺度拓展研究的热点。     

Growth and water relations of walnut trees (<Emphasis Type="Italic">Juglans regia</Emphasis> L.) on a mesic site in central Italy: effects of understorey herbs and polyethylene mulching

The establishment of trees and associated herbaceous understorey vegetation during the afforestation of former arable lands can decrease soil erosion, increase soil fertility and diversify plantation income. This study reports on the five-year results from experimental plots of common walnut (Juglans regia L.) established in association with two different herbaceous understoreys in 1994 in central Italy. Treatments included: (i) walnut established with plastic film mulching in association with subclover (Trifolium subterraneum L.); (ii) walnut with subclover; (iii) walnut with a spontaneous herbaceous cover (grassing treatment); (iv) clean-cultivated walnut (control). Stem growth rates and the periodical changes in predawn and midday leaf water potentials of walnut, as well as the annual sward dry matter production, were measured. Over the five-years, the understorey vegetation was competitive towards trees, negatively affecting their leaf water status relative to the control, especially during mid-summer observations, with the onset of summer drought. Tree growth in the grassing treatment was slightly but significantly (p < 0.05) reduced in height in comparison to unmulched trees with subclover. Subclover competitiveness towards walnut was completely masked by the plastic mulching, so that mulched walnut with subclover had the highest cumulative stem diameter and height (+20% than control treatment). This was associated with water potentials that were never higher than the control. The subclover-mulched treatment, due to its three main advantages (highest cumulative stem growth, an annual dry matter fodder production of 6.3 t/ha, and soil erosion protection), appears to be a promising cultural model for walnut cultivation in areas without marked drought.     

大兴安岭林区伐区风倒风折原因探讨

大兴安岭是全国重点林区之一,素有"绿色宝库"之称。但是,由于40多年开发建设的采伐和自然灾害的影响,目前已经陷入资源枯竭境地,成熟林和过熟林资源所剩无几。分析认为,在现实调查设计规程和实际林木采伐过程中,由于对主伐的采伐强度限制过宽,从而造成"采一片,倒一片"的局面,资源浪费严重。同时为森林火灾和森林病虫害发生、发展和漫延创造了条件。建议林业法规制定部门,能够根据林业当前实际情况,结合林业生态发展战略,修改制定符合现代林业发展规律的法律法规,使森林资源最大限度得以保护。     

循环水结垢和腐蚀的机理及其控制

从理论上论述了循环水系统水垢的形成和水对循环系统的腐蚀机理，指出，当循环水系统普遍存在结垢时，由于水垢隔绝了金属与水的接触，腐蚀不会发生；而当水垢倾向于溶解时就会发生腐蚀，水垢的形成主要是由于循环水中含有碳酸钙。     

A controlled,hierarchical study of habitat fragmentation: responses at the individual,patch, and landscape scale

We compared the performance of individuals and whole populations of meadow voles, Microtus pennsylvanicus, within and between experimentally created habitat fragments of three sizes (1.0, 0.25, and 0.0625 ha) and between a 20-ha fragmented and a 20-ha continuous habitat landscape. We recorded 10,020 captures of 3946 individuals over 17 censuses between June 1993 and October 1994. Five demographic parameters showed significantly different population responses between the two landscapes but no difference in tests comparing fragment size: i.e., mean and peak population densities (the latter, in each of the two growing seasons) averaged 149 to 172% higher, population growth rate averaged 219% higher, and adult recruitment 170% higher in fragmented than in the continuous control landscape. Observations at the individual level (body sizes, rates of reproduction, residence times) suggested that these landscape differences involved enhanced performance of adult females associated with edge habitats rather than differential immigration or emigration. If this turns out to be a common response to fragmentation, the detection of such responses will be greater when comparing fragmented and unfragmented landscapes with qualitatively different structure than for fragments of varied size with differing proportions of edge. That responses to habitat fragmentation may be more evident at the very small (individual) and very large (landscape) scales, but may be obscured at the intermediate spatial scale of fragments, is a proposition that clearly requires more attention.     

Field-simulator studies of insecticide resistance to dimethylcarbamates and pyrethroids conferred by metabolic- and target site-based mechanisms in peach-potato aphids,Myzus persicae (Hemiptera: Aphididae)

A range of insecticides was applied at recommended application rates against populations of Myzus persicae (Sulzer) carrying various combinations of three insecticide resistance mechanisms (carboxylesterase-based metabolic resistance and two target-site mechanisms, known as MACE and kdr), supported on either Chinese cabbage or potatoes in field simulator cages. Patterns of response were similar on both host species. MACE conferred extreme resistance to pirimicarb and triazamate (dimethylcarbamate insecticides). The kdr mechanism was associated with resistance to lambda-cyhalothrin, cypermethrin and deltamethrin (pyrethroid insecticides). A mixture of pirimicarb plus lambda-cyhalothrin was only effective against M persicae not carrying kdr or carrying kdr and low carboxylesterase-based resistance. None of the insecticides tested was effective against M persicae carrying both MACE and kdr resistance. The implications of these findings for the formulation of control strategies, based on regular monitoring of resistance genotype frequencies, are discussed.     

中草药对蛋鸡生产性能的影响

通过对比补泻结合的中草药添加剂与市售增蛋类方药以及泻肾类方药对蛋鸡生产性能方面的影响,探索以补泻结合为指导思想的辨证组方在提高蛋鸡的产蛋率,增强蛋鸡免疫机能和抗病力等方面的作用.试验结果表明,该添加剂对产蛋率、饲料转化率等性能均有显著提高.按0.25%、0.50%、1.0%比例添加,产蛋率较对照组提高4.25%、5.4%、6.35%,(P<0.01).     

贵州省烟田蚜虫的种类和田间定殖情况

研究了贵州省烟田蚜虫的种类,结果表明:迁入到烟田的蚜虫隶属9种,其中桃蚜(Myzus persicae)、甘蓝蚜(Brevicoryne brassicae)、豆蚜(Aphis craccivora)、萝卜蚜(Lipaphis erysimi)、麦长管蚜(Macrosiphum miscanthi)占诱集蚜量的90%以上,尤以桃蚜数量最大,是烟田传播病毒病的主要蚜种,能传播多种烟草病毒病。试验结果还表明,单作烟田和毗邻油菜的烟田病毒病发病较高,麦套烟的发病较轻;甘蓝蚜、豆蚜和萝卜蚜基本上不能在烟叶上定殖。     

农村电网接地引下线腐蚀机理及新型防腐措施

农村电网覆盖面广,不同的土壤条件、缺乏维护及低成本设备缺陷造成农村电网接地引下线腐蚀问题严重。而接地引下线的腐蚀有着不同于接地网的腐蚀机理,即多种环境与化学作用的综合体现,所以农村电网接地引下线需要新的防腐措施。通过对已有研究成果探究,本文提出了包覆法结合牺牲阳极法的农村电网接地引下线防腐新措施,并对其实现进行了论述。