不同能量水平对朗德鹅生长曲线的影响研究

在不同能量水平下,运用Logistic模型和Gompertz模型对朗德鹅0～10周龄生长曲线进行了分析和非线性曲线拟合研究。结果表明,不同生长阶段,朗德鹅公鹅、母鹅的适宜能量水平不同,Logistic模型和Gompertz模型都能很好地拟合朗德鹅的生长曲线,但Gompertz模型在拟合度和预测体重效果方面相对较好。中等能量水平下,2周龄前公鹅、母鹅的生长曲线基本一致,之后公鹅则明显高于母鹅,且保持较长时间的快速生长状态,公鹅的拐点体重显著高于母鹅,但拐点日龄的出现却晚于母鹅。     

大果沙棘实生苗年高生长节律的研究

大果沙棘实生苗的年高生长进程呈现慢-快-慢的"S"形节律,用logistic模型分析其连续性和阶段性收到良好效果。研究表明,整个生长进程中存在着明显的速生期(长约43d),速生期内的苗高生长量约占总生长量的58%。在育苗实践中要切实抓住这一关键时期,采取有效管理措施,提高苗木质量。     

A GIS-based plant prediction model for wetland ecosystems

An existing non-spatial model for the prediction of response of wetland plant species on ecological factors has been transformed into a GIS-based prediction model which produces spatial output at the landscape scale. The input, spatial patterns of the ecological factors, were constructed with geostatistical spatial interpolation (kriging). With this GIS-based model the spatial patterns of presence and absence of 78 wetland plant species are predicted for an area with wetlands in the Netherlands of approximately 500 square kilometers. The GIS-based model has been validated, and the estimated uncertainty of the input has been propagated through the model. At the species level the output shows spatially coherent and non-random patterns. The validation is affected by the propagation of input errors through the model. The number of valid predictions declines approximately 10–20% when 95% confidence intervals are used in the validation. This study shows that it is feasible to use a geostatistical interpolation method to construct spatial patterns of ecological factors on a landscape scale and to use these patterns as input for a GIS-based prediction model. The added uncertainty on the input values however, affects the number of valid predictions of the model.     

两系杂交稻稻曲病发生规律及防治

为控制日益严重的两系杂交稻稻曲病的危害，分别对不同杂交组合按新分级标准系统调查田间病情，并进行多种田间小区药剂试验和综防示范，探讨两系杂交稻稻曲病的发生规律及防治措施，结果表明，两系杂交稻稻曲病的发生与组合的抗性密切相关，稻曲病的田间发生用逻辑斯蒂曲线模型拟合，防治稻曲病的药剂以瘟曲克星的防效最好，防治适期足水稻孕穗未期至破口期。对感病绘经剂防治药两次比施药一次效果好；以推广抗病 基础的综合防治措施切实行可行，防治效果显著。     

旱稻籽粒灌浆过程及其矿质元素的研究

1986,1987年对5个旱稻品种不同生育期和不同密度的研究表明,籽粒干物质积累过程符合 Logistic 生长曲线,并达到极显著水平。籽粒可溶性糖和淀粉的变化趋势品种间大致相同,抽穗后第7天转运到籽粒的可溶性糖最多,之后,淀粉积累速率加大,抽穗后第27天淀粉含量达最高值。籽粒蛋白质积累在品种间差异较大。籽粒矿质元素以小白旱稻为最高,A7910次之,其它三个品种相差不大。     

岩羊和马鹿对人与机动车反应的差异分析

人为干扰会对野生动物种间关系、个体适合度、群落结构和繁殖成功率等产生中长期的影响。因此,研究野生动物反干扰行为对于我们认识该物种对其生境的行为适应和进化机制具有重要意义。2017年11—12月在内蒙古贺兰山国家级自然保护区内通过建立多元逻辑斯蒂回归模型研究了岩羊(Pseudois nayaur)、马鹿(Cervus elaphus)的反干扰策略,本研究共设置33条样线,记录了10种在人为干扰下可能会影响岩羊、马鹿反应行为的变量,经模型分析发现影响岩羊反应行为的变量有5种,影响马鹿反应行为的变量有4种,共同影响因子分别是干扰源、性别、头的朝向和地形特征,而植被类型则只对岩羊产生影响。最后根据逻辑模型得出的数据计算发生比,从而了解各个分类变量与反应行为的关系。     

农产品供应链对农户减贫增收的关联效应分析——基于滇、桂、苏、闽四省(区)的实证

实现小农户与大市场的有效对接既是现代农业健康发展的必然要求,又是贫困农户减贫增收的现实路径。在农业市场化改革深入推进的背景下,通过培育农产品供应链以此带动农户减贫增收致富,是当前市场化减贫的重要方向。基于滇、桂、苏、闽四省(区)农户调查数据,采用多元有序Logistic模型,分析了农产品供应链对农户减贫增收的关联效应及区域差异。结果表明,农产品供应链对农户减贫增收具有正向作用,加入农产品供应链能显著增加农户收入,而且对欠发达地区的作用发挥优于发达地区。有无加工销售、农产品出售渠道、对供应链管理认可程度等供应链融入状况关键因素对农户减贫增收影响明显。因此,重视采取整合区域农业资源与要素,培育优势农产品供应链;协调农产品供应链主体关系,构建小农户稳定融入机制;加快农村基础设施建设步伐,深入推进农业市场化改革进程等优化措施,方能充分发挥农产品供应链对农户减贫增收的带动效应。     

基于空间Logistic的山西省火灾风险评价与火险区划

利用山西省2002-2012年MODIS卫星遥感数据,建立了描述火灾空间分布及其影响因子的空间Logistic风险模型,从省域空间尺度和较长时间尺度上,开展火险评价与火险区划研究。结果表明,通过空间采样构建的Logistic火灾风险模型拟合效果很好。在显著性水平为0.05的情况下,通过模型系数检验和Wald检验,相对运行特征值(ROC)为0.757。经图层运算得到火烧概率分布图,并将山西省分为无火险区、低火险区、中火险区、高火险区和极高火险区。对山西省火灾风险空间变化影响较为显著的因子为高程(GC)、土地利用类型(LT)、地表温度(LST)、归一化差值植被指数(NDVI)和全球植被湿度指数(GVMI),对火灾风险空间变化影响不显著的因子则仅有坡度(PD)和道路可达性(DL)。NDVI和LST对火灾影响在省内全局显著,而GC、LT和GVMI仅对省内部分地区的火灾影响显著。山西省按火灾影响因素可划分为7类区域,不同类型区域应确定不同的防火重点,制定差别化的防火策略。     

农户种草意愿及其影响因素的实证分析

为寻求促进扩大栽培牧草种植面积的有效途径,本研究对西藏拉萨、日喀则和山南地区的797个农户的种草意愿情况进行调查,并采用Logistic回归分析对影响该地区农户种草意愿的因素进行分析。结果表明,农户的受教育年限、家庭总收入、耕地总面积、牲畜头数、牧草种子来源受到政府或项目支持及农户参加牲畜合作社对农户种草意愿具有积极的影响,而家庭劳动力人数对种草意愿具有负向影响。其中,户主年龄、家庭人口数和户主是否有村干部或科技特派员经历3个因素对种草意愿无显著影响。基于以上研究结果,本研究提出了加快普及种草养畜相关知识、研发适宜农区种草相关技术和加强牧草种植补贴额度的对策。     

Analysis of horse movements from non-commercial horse properties in New Zealand

AIMS: To investigate property-level factors associated with the movement of horses from non-commercial horse properties, including the size and location of the property, number and reason for keeping horses.

METHODS: Using a cross-sectional survey 2,912 questionnaires were posted to randomly selected non-commercial horse properties listed in a rural property database. The survey collected information about the number of horses, and reasons for keeping horses on the property, and any movement of horses in the previous 12 months. Three property-level outcomes were investigated; the movement status of the property, the frequency of movement events, and the median distance travelled from a property. Associations were examined using logistic regression and Kruskal-Wallis analysis of variance.

RESULTS: In total 62.0% (488/791) of respondents reported at least one movement event in the year prior to the survey, for a total of 22,050 movement events. The number of movement events from a property varied significantly by the number of horses on the property (p<0.02), while the median distance travelled per property varied significantly by both region (p<0.03) and property size (p<0.01). Region, property size, the number of horses kept, and keeping horses for competition, recreation, racing or as pets were all significantly associated with movement status in the multivariable analyses (p<0.001).

CONCLUSION AND CLINICAL RELEVANCE: This study showed that there are characteristics of non-commercial horse properties that influence movement behaviour. During an exotic disease outbreak the ability to identify properties with these characteristics for targeted control will enhance the effectiveness of control measures.