近30 a来黑龙江省气候变化及其对玉米产量的影响

基于全球气候变化,以黑龙江省为例,在收集1980-2009年气象站点农业气象资料的基础上,运用线性倾向率方法,分析了近30 a来黑龙江省玉米生长季和3个主要生育阶段的气候变化特征;在此基础上分析了玉米气象产量与不同生育阶段气候要素的相关性。结果表明：平均、最高和最低温度指标从时间变化来看,在各个生育阶段都表现为升高趋势,从空间变化来看,温度升高趋势基本表现为从东到西的增加趋势;日照时数和参考作物蒸散量的变化从时间上来看,除在播种-苗期表现为减少趋势外,在其他生育阶段都表现为增加趋势;从空间上来看,其变化幅度在各个生育阶段基本上表现为从西南向东北递增的趋势;降水量时间上主要表现为减少趋势,空间变化趋势则不明显。相关分析表明：穗期和花粒期的最低温度与玉米的气象产量呈正相关关系,花粒期的最高温度与玉米的气象产量呈负相关关系。     

牡丹‘凤丹’体细胞胚发生技术

为建立牡丹‘凤丹’体细胞胚发生培养体系,以牡丹‘凤丹’的合子胚、胚轴和子叶为外植体进行离体培养,研究了种胚发育时期不同质量浓度蔗糖处理及不同的培养基对牡丹体细胞胚发生的影响,结果表明,花后110 d是体细胞胚直接诱导合适的发育时期,诱导率为33.00%,3种外植体中,种胚的诱导率最高;利用质量浓度为90 g.L-1的蔗糖溶液处理种胚2 h,体细胞胚诱导效果最好,在MS+2,4-D 2.0 mg.L-1+6-BA 2.0 mg.L-1培养基上获得较高的体细胞胚,诱导率为38.33%。     

农民外出务工背景下的耕地抛荒现象分析——以吉林省通化市长白朝鲜族自治县为例

根据在长白山朝鲜族自治县的调研情况,从区域经济和社会学两个角度出发来分析该地区耕地弃荒的现状,深入剖析该地区耕地弃荒的原因,并提出了杜绝耕地弃荒的对策。     

基于成长阶段性需求的高校青年教师培养机制研究——对河北农业大学的调查与思考

基于对河北农业大学375位青年教师的调查数据,对青年教师在不同成长阶段的需求特征进行了分析。结果表明,青年教师在入职适应期、蓄势发展期和最佳创造期表现出的需求既有共性也有个性特征。针对这些需求,提出从教学能力培养、科研指导、学历进修、职称晋升等角度出发,构建全方位、立体培养机制,以促进青年教师的职业发展。     

Construction Stage Analysis on Replacement of Closure Segment in Prestressed Concrete Cable-stayed Bridges

To deal with failure of wet joint between a closure segment and its neighboring segments of main girder in an existing prestressed concrete cable-stayed bridge, the technology on replacement of closure segment was presented. In order to analyze structural characteristics of this technology, its technical approaches and construction key points were introduced. Then a FEM model for a typical prestressed concrete cable-stayed bridge was established, and a construction stage analysis method was given in detail, including establishing a structural basement calculation model for replacement of closure segment and simulating its construction procedures. Based upon calculation results, variations of some structural state parameters with construction stages, such as deck deflection of main girder, longitudinal horizontal displacement at the top of pylons, cable forces, were analyzed. The results showed, this method could reflect actual change process of structural state and existing inspected results of cable-stayed bridge, and FEM results could well meet with construction monitoring results during replacement of closure segment. Thus variations of structural characteristics with construction stages could actually be revealed. This method could provide references for design and construction control of replacement of closure segment in existing prestressed concrete cable-stayed bridges.     

甘肃小陇山日本落叶松人工林不同发育阶段土壤理化性质的变化

采用时序研究法对甘肃小陇山林区日本落叶松人工林不同发育阶段(6、15、23、35 a)的土壤物理性质、化学性质进行多因子综合比较,利用主成分分析的方法,以主成分特征贡献率为权重,计算土壤肥力综合指标值,分析土壤性质的演变规律。结果表明:日本落叶松人工林发育至近熟林阶段,土壤物理性质变差,表现为土壤密度最大1.62g·cm-3,毛管孔隙度和最大持水量降至最低,分别为29.69%、24.45%,并且土壤有机质、氮、磷、钾、镁、钙含量也明显降低;而到成熟林阶段,土壤理化性质有显著改善,土壤密度降低为1.21 g·cm-3、毛管孔隙度和最大持水量恢复至45.56%、42.65%,土壤养分含量也有了很大的提高,甚至超过了中龄林阶段的水平;同时幼龄林、中龄林、近熟林和成熟林土壤性质综合得分分别为-0.329、0.188、-0.565、0.739,也表明近熟林土壤性质最差,成熟林土壤性质最好。     

增温补光育苗对浓香型烤烟大田生长和理化指标的影响

研究了苗期不同光温条件下培育的烟苗移栽到大田后,其生育期、生长速率、理化指标及其产量的变化。结果表明,烤房人工光源育苗、大棚恒温补光育苗、大棚恒温育苗移栽大田后,其生育期、生长速率和成熟期的农艺性状均优于大棚常规育苗,其中有效叶数和茎高的差异均达到极显著水平;初烤烟叶的宽长比、单叶重、厚度、干物质重和单位面积质量等物理指标均极显著优于对照;但烤房人工光源育苗和大棚恒温补光育苗处理的初烤烟叶总糖及还原糖极显著低于对照和其余处理;主要经济性状表现为烤房人工光源育苗〉大棚恒温补光育苗〉大棚恒温育苗〉大棚常规育苗。因此,苗期采用增温补光处理不仅可显著改善烟苗素质,而且对烤烟大田生育期的烟叶理化指标和产量有显著影响。     

Treatment Abandonment in Feline Sporotrichosis – Study of 147 Cases

This study describes the epidemiological, clinical and mycological aspects of feline sporotrichosis cases attending the Laboratory of Clinical Research on Dermatozoonosis in Domestic Animals – Evandro Chagas Clinical Research Institute (LAPCLIN‐DERMZOO/IPEC/FIOCRUZ), from 1998 to 2005. It was possible to get in contact with 147 (19.2%) cat owners. One hundred and thirteen (76.9%) cats were male, 117 (79.6%) had no defined race and 87 (59.2%) were sexually intact. The age ranged from 72 to 216 months (median = 108 months). Nineteen cats were reassessed: eleven (57.8%) were male, thirteen (36.8%) were breed and fifteen (47.3%) castrated. Fourteen (52.6%) animals lived at home and did not roamed the streets. Seven (36.8%) had normal clinical findings and negative mycological examination. Twelve (63.1%) cats had skin lesions compatible with sporotrichosis. Thirty‐one (21%, n = 147) cats disappeared after abandoning treatment, 36 (24.5%, n = 147) were alive and 80 (54.4%, n = 147) had died. Causes of death informed by the owners were: sporotrichosis in 35 (43.7%, n = 80), accidental death in 27 (33.7%, n = 80) and other diseases in 18 (22.5%, n = 80). Withdrawal of treatment occurred mainly at the time of clinical improvement and may represent a serious obstacle to the control of sporotrichosis.     

基于联合变化检测的耕地撂荒信息提取与驱动因素分析

撂荒地遥感提取方法主要为分类方法和变化检测方法。由于撂荒地覆被类型复杂,容易同草地、灌木混分,导致分类方法的提取精度不高。而变化检测方法易受非耕地变化因素干扰,且只能提取监测周期内的新增撂荒,无法提取监测周期之前的历史撂荒。此外,受遥感数据本身的制约,中低分数据受混合像元干扰而提取能力不足,高分遥感易受地形起伏、云层遮蔽、覆盖周期长等因素干扰而损失精度,因此,传统遥感方法提取撂荒地困难。本研究提出多源数据联合变化检测方法以提取撂荒地。利用多源数据的异质性和不同方法的互补性,针对不同类型的撂荒地制定不同的提取策略,并进行耦合分析以提取撂荒地。经实地调查验证,该方法提取总精度达到97. 6%。在此基础上,提取撂荒地的距离特征、高差特征、灌溉特征和邻域特征等自然地理指标,对其进行了显著性分析,判别了区域撂荒主导因素,为撂荒驱动力研究、定向提升撂荒地管理提供了依据。     

Long‐term effects of mulching,traditional cutting and no management on plant species composition of improved upland grassland in the Czech Republic

A shortage of available livestock for utilizing grassland biomass in Central Europe is challenging for the management of both semi‐natural grasslands and previously intensified (limed, fertilized and reseeded) upland grasslands. An alternative method of grassland management is mulching, in which aboveground biomass is cut, crushed and subsequently spread on the surface. This paper reports on an experiment to compare three different mulching frequencies (one, two and three times per year) with an unmanaged treatment and traditional management of two cuts per year (control) on a previously improved upland meadow. Plant species composition was monitored over 13 years. Traditional management of two cuts with biomass removal was the most suitable method for maintaining plant species richness and diversity, and both were reduced significantly in the once‐mulched and especially in the unmanaged treatment. Tall dicotyledonous weeds such as Urtica dioica, Cirsium arvense and Aegopodium podagraria were promoted by the unmanaged treatment and by mulching once a year. Higher frequency of defoliation had positive effects on the spread of short forbs such as Taraxacum spp., Plantago lanceolata and Trifolium repens. After eight years, there were changes in sward structure in the unmanaged and mulched‐once‐a‐year treatments, with increase in the tall/short species ratio. In conclusion, repeated mulching cannot substitute fully for traditional two‐cut management in improved upland meadows without decreasing plant species richness and diversity, and changing the sward structure. Although mulching once a year may prevent invasion by shrubs and trees, it also supports the spread of weedy species similar to no management.