Factors affecting the adoption of agroforestry practices by farmers in Cameroon

This paper presents empirical evidence on the impact of socio-economic factors on the adoption of agroforestry practices in Cameroon. The analysis uses primary farm-level data collected from June to December 1996. Three major provinces of the country were covered, namely Centre, Southwest and Northwest Several agroforestry technologies have been promoted among farmers in the zone, including alley farming, improved fallow, live fencing, cut-and-carry fodder and apiculture. The status of adoption of each agroforestry practice is described and factors that affect adoption identified. These are gender of farmer, household family size, level of education, farmer’s experience, membership within farmers’ associations, contact with research and extension, security of land tenure, agroecological zone, distance of the village from nearest town, village accessibility and income from livestock. Research findings indicate that since factors affecting farmers’ adoption of agroforestry practices differ across techniques, generalisation is to be avoided.     

大兴安岭林区一次飞机增雨作业的条件识别和效果分析

应用GRAPES模式预报资料、卫星云特征参量产品、L波段探空数据、雷达资料等,对2015年6月6日大兴安岭林区一次飞机增雨作业过程进行条件判别并初步分析了作业效果。结果表明,GRAPES模式对云宏观场的模拟效果较好,云带范围、云顶高度、云顶温度、发展趋势与实况基本一致,垂直累积过冷水含量及其水凝物的预报为作业条件的识别提供了重要参考;作业后影响区内降水回波面积增大、回波增强,云层增厚,垂直累积液态水含量有所增加。     

基于主成分分析和聚类分析的贵州烟叶品质类型划分

本研究把烟叶外观质量评价和常规化学成分评价相结合,建立基于主成分分析和聚类分析的Fisher判别函数的烟叶质量评价模型,对贵州烤烟的品种类型进行划分,旨在为烟叶质量评价提供科学方法,并在生产上进行指导。     

主成分聚类分析在县域生态经济分区中的应用——以东营市河口区为例

生态经济分区是宏观管理区域社会经济发展的一种新的模式.在介绍县域生态经济分区原则与方法的基础上,以东营市河口区为例,首先从资源环境、社会、经济3方面共选取27个指标构建了分区指标体系,然后以乡镇为样本进行主成分分析,再利用提取的主因子作为新的综合变量,并以各主因子得分矩阵为新的综合变量数据进行聚类分析,在考虑地形地貌和区域特征的基础上将该县域划分为4个生态经济区.在分析各生态经济区基本情况的基础上为各区经济发展方向提出了建议.     

Management of burnt wood after fire affects post-dispersal acorn predation

The management of burnt wood after a fire may affect seed predation by vertebrates due to the change produced in habitat structure. We analyze the effect of burnt wood management on post-dispersal seed predation in the Holm oak. Three plots were established in a burnt forest, with three treatments per plot: (1) non-intervention (NI, all trees left standing), (2) “partial cut plus lopping” (PCL, felling 90% of trees, cutting their main branches, leaving all the biomass in situ), and (3) “salvage logging” (SL, felling the logs for their removal and masticating the woody debris). Acorns were buried to mimic dispersal by jays or rodents two and three years after fire, with two trials per year (7200 monitored acorns), and the predation rate was evaluated until the time of seedling emergence. The spatial patterns of acorn predation were assessed by computing a transformed-Ripley's K function and Moran's I correlograms. There was a large spatial and temporal variability in acorn predation, with differences among trials, plots, and replicates within treatments and plots. Overall, PCL showed the lowest predation values (83.0% versus 87.4 in NI and 88.0 in SL). Predator species (mice versus wild boar) also differed among treatments, wild boar having a negligible effect in PCL, presumably due to the physical barrier of felled logs and branches. The results support that: (1) salvage logging offers no advantage against predators and (2) that post-fire burnt wood management alters the guild of acorn predators and may reshape the pattern of seedling establishment.     

气象要素时间分辨率对参考作物蒸散估算的影响

参考作物蒸散(reference evapotranspiration,ET0)的准确估算是农业水资源合理利用的重要环节。为了明确气象要素不同时间分辨率对参考作物蒸散估算的影响,该文基于寿县国家气候观象台2007-2013年观测资料,将1min时间分辨率数据平均值作为真实值,分析了10、20、30、40、60 min、4次/d(02:00、08:00、14:00、20:00)和3次/d(08:00、14:00、20:00)这7种不同时间分辨率对逐日气温、风速、太阳辐射、相对湿度和日、月及年参考作物蒸散(ET0)估算的误差情况。结果表明:ET0和气象要素的误差整体上随时间分辨率降低而增大。4个气象因子中,日平均风速估算受时间分辨率变化的影响最显著,误差最大;其次是太阳辐射。逐日ET0估算在7种时间分辨率的平均绝对相对误差(mean absolute relative error,MAPE)依次为0.53%、1.01%、1.38%、1.72%、2.46%、4.72%和6.14%,表明10至60min时间分辨率的估算效果相较3次/d和4次/d有明显改善。10至40 min的绝对误差超过95%都在-0.20~0.20 mm/d区间内,误差较小且集中度高;太阳辐射时间分辨率变化对ET0估算误差贡献最大,其次是风速,这主要是由于两个要素本身对分辨率较敏感且分别是ET0辐射项和动力项的主要组成因子。时间分辨率的变化对累计后长时间尺度ET0的影响较小,月和年ET0的误差明显小于逐日ET0,月ET0在7种时间分辨率的MAPE值依次为0.13%、0.21%、0.27%、0.40%、0.50%、1.18%和1.48%;各年ET0相对误差(relative error,PE)的绝对值多数均小于0.50%。     

柴油机燃烧甲醇/生物柴油尾气颗粒物热解特性分析

采集了甲醇/生物柴油(5%、10%、15%)混合燃料在柴油机燃烧的尾气颗粒。采用热重分析仪和切线法、Flynn-Wall-Ozawa(FWO)热解动力学方法,研究颗粒挥发及氧化规律,分析了颗粒热解特征温度和活化能。结果表明:随着甲醇掺混量的增加,颗粒中H_2O的质量分数由2.6%增加到3.5%,可溶有机物(soluble organic fraction,SOF)质量分数由26.1%增加到32.5%,SOF的质量变化速率增大,对应的峰值温度后移;在O_2氛围中,SOF挥发阶段与在N2氛围中的表现基本一致,但质量变化速率明显增大;碳烟(soot)质量减小,由70.3%减少到63.8%,soot质量变化率峰值增大;SOF析出温度变化较小,soot起始燃烧温度明显降低,由488℃降低到458℃,SOF起始燃烧温度与燃尽温度均有所降低,颗粒的热解总反应时间缩短;颗粒的热解反应活化能由140.3 k J/mol降低117.3 k J/mol,颗粒的热解性能增强,颗粒更易被氧化。研究结果可为甲醇/生物柴油燃烧颗粒的处理及柴油机颗粒捕集器(diesel particulate filter,DPF)再生提供依据。     

影响烤烟评吸质量的主要化学成分研究

影响烤烟评吸质量的主要化学成分研究王允白王宝华郭承芳王凤龙周健（中国农业科学院烟草研究所,山东青州２６２５００）ＳｔｕｄｙｏｎｔｈｅＭａｉｎＣｈｅｍｉｃａｌＣｏｍｐｏｎｅｎｔｓＲｅｌａｔｅｄｔｏＳｍｏｋｉｎｇＱｕａｌｉｔｙｉｎＦｌｕｅ－ｃｕｒｅｄＴｏ...     

涪陵南沱茎瘤芥种植基地环境质量评价--土壤重金属

采用环境调查的方法研究了涪陵南沱镇茎瘤芥种植基地土壤重金属含量。结果表明,该区域土壤整体上重金属污染水平较低,基本没受到汞和铬污染,但已受到了铜、铅、镉污染,特别是镉污染已经相当严重。相关分析和回归预测分析均表明土壤养分对土壤重金属含量有较大影响。