Seeding cool-season grasses into unimproved warm-season pasture in the southern Great Plains of the United States

Limited availability of herbage during the cool season creates a problem of a supply of nutrients for livestock producers throughout the southern Great Plains of the USA and, particularly, on small farms where resource constraints limit possible mitigating strategies. Six cool‐season grasses were individually sown into clean‐tilled ground, no‐till drilled into stubble of Korean lespedeza [Kummerowia stipulacea (Maxim) Makino] or no‐till over‐sown into dormant unimproved warm‐season pastures. The dry matter (DM) yields of mixtures of cool and warm‐season herbage species were measured to test their potential for increasing cool‐season herbage production in a low‐input pasture environment. Only mixtures containing Italian ryegrass (Lolium multiflorum Lam) produced greater year‐round DM yields than undisturbed warm‐season pasture with all establishment methods. When cool‐season grass was no‐till seeded into existing warm‐season pasture, there was on average a 0·61 kg DM increase in year‐round herbage production for each 1·0 kg DM of cool‐season grass herbage produced. Sowing into stubble of Korean lespedeza, or into clean‐tilled ground, required 700 or 1400 kg DM ha^?1, respectively, of cool‐season production before the year‐round DM yield of each species equalled that of undisturbed warm‐season pasture. Productive pastures of perennial cool‐season grasses were not sustained beyond two growing seasons with tall wheatgrass [Elytrigia elongata (Host) Nevski], intermediate wheatgrass [Elytrigia intermedia (Host) Nevski] and a creeping wheatgrass (Elytrigia repens L.) × bluebunch wheatgrass [Pseudoroegneria spicata (Pursh)] hybrid. Lack of persistence and low productivity limit the usefulness of cool‐season perennial grasses for over‐seeding unimproved warm‐season pasture in the southern Great Plains.     

湖北省南方型杨树引种气候区划

选择≥10℃积温、温暖指数、年降雨量、极端最低气温、无霜期和年均气温6个气象要素,运用模糊数学方法,计算湖北省所有县（市、区）与固定样本（潜江）的相似程度,按照加权和数的大小。结合南方型杨树的生态学特性,将湖北省南方型杨树的引种栽培区划分为最适宜区、适宜区和不适宜区,推荐各区域的适栽品种．     

南方红黄壤地区草地资源特点与开发利用

南方红黄壤地区可利用草地面积大,水热自然条件优越,天然牧草丰富、产量高,具有广阔的开发前景.但该区草地分布零散,且地形多为山地丘陵,土壤肥力低下,土地质量不高, 水土流失严重,草地管理粗放,草场退化严重.因此,草地开发中应注意用养结合,针对不同立地条件,采取相应的开发利用途径:中高山地区,加快人工草场建设,解决饲草旺季余缺矛盾;丘陵区,加快发展幼林间种草,实行林草结合,改善生态环境;广大农区 ,加快扩大冬闲稻田种草,推行粮草轮作,提高土地利用率取得良好的经济效益.     

基于向量模法的陕南地区水环境承载力评价

在论述水环境承载力概念的基础上,结合陕南地区的水环境现状,通过构建指标体系,应用向量模法对陕南地区2000-2007年的水环境承载力进行了评价.计算结果表明,陕南地区水环境承载力的变化呈现波动趋势,但逐渐趋于平缓.并针对陕南地区的具体情况,提出了加强区域水源涵养与水源地保护、调整产业布局、加快污水处理设施建设、加大小型水利工程建设和建立水资源补偿机制等对策措施.     

基于MODIS的南方草地NPP遥感估算与应用

草地NPP遥感模型的构建是实现大面积草地NPP估算的有效途径之一。以MODIS-NDVI数据为基础,以南方草山草坡为研究对象,结合野外实测数据,分析了草地NPP与NDVI之间的关系,同时构建了以NDVI为自变量以及水热条件为调节因子的南方草地NPP遥感估算模型,并通过不同年份独立的实测数据对模型进行了验证。结果表明,南方草地NPP与NDVI之间存在5种相关类型,均达到了极显著水平。NPP的模拟值和实测值之间具有很好的相关性和一致性,5种草地类型R²分别为0.902 2,0.826 6,0.871 2,0.887 7和0.875 5,均达到了极显著水平,均方根误差(RMSE)和相对均方根差(RRMSE)均较小。表明模型的模拟结果比较可靠,为南方草地NPP估算及草地资源管理提供了一种有效的方法。     

意大利野生动物保护管理

我国野生动物保护工作正面临着新的机遇和挑战,借鉴其他国家相关经验,对加强野生动物管理、提升保护工作整体水平很有帮助。文中介绍了意大利野生动物保护管理体制、机制和策略,归纳分析了该国在保护理念、物种和种群动态监测、科学研究、危害控制等方面的有益做法。在此基础上,针对野生动物保护管理中的薄弱环节,提出了宣传普及科学保护理念、健全相关法律规章、完善和创新管理模式等有关对策建议,以期为促进我国野生动物保护事业发展提供参考。     

Assessing the efficiency of the Italian aquaculture firms

Abstract

The study investigates the efficiency of a sample of Italian aquaculture firms according to their legal status, size, and location. An efficiency analysis was conducted for a sample of 160 units using an output-oriented Data Envelopment Analysis. The average value of the efficiency scores reveals that it should be possible to significantly increase firm performance. The most inefficient farms are cooperatives, southern farms, and the smallest farms. The weight of efficient units is as follows: 34% of the cooperatives and 26% of the limited liability companies; 26% of units located in Northern-Central regions and 34% of those placed in Southern areas; 47% of the big and 23% of the small firms. Among subgroups of units, the only significant difference in the average efficiency score is related to the firm size. The sensitivity of the results to methodological choices reveals that the variable return to scale hypothesis fits the data better than the constant returns to scale and that bootstrapping while changing the value of the scores does not change findings in terms of size, location, and legal status. Actions which remove obstacles and increase firm size are the most obvious ways to improve the efficiency and competitiveness of the sector.     

基于微气候改善的江南古典园林空间形态的研究

以江南古典园林的代表作——苏州拙政园、留园为例,定点实测园林中的微气候参数,如空气温度、相对湿度以及风速等。分析微气候在近地面的状态与古典园林空间布局的关系,定性定量地解读江南私家造园的空间营造理法。结果表明,园林中的水体对微气候的优化效果最为明显,植物配置对微气候的优化主要体现在风速及湿度上,建筑形式会影响场地的温度及风力,场地地势的高低会明显影响场地风力的大小。     

南亚热带杉木林改造对土壤及凋落物持水能力的影响

对杉木林进行改造,是提高林分质量和生态效能的重要措施。该文研究了杉木林改造前期对土壤及凋落物持水能力的影响。结果表明,在杉木林改造前期,不同林龄段试验林间土壤容重、孔隙度和土壤持水量差异不显著（P > 0.05）,但随林龄的增加呈上升趋势,土壤涵养水源能力有所增加。凋落物量及其持水能力随改造林龄的增加呈上升趋势,9～11 a林龄试验林凋落物及持水能力显著高于3～5 a林龄试验林（P < 0.05）,而其凋落物持水能力与5～7 a林龄试验林差异不显著（P > 0.05）。浸水试验表明,凋落物持水率随浸泡时间的增加呈对数曲线增长,吸水速率与浸泡时间呈反函数关系。凋落物最大持水量远小于土壤最大持水量,仅为土壤的0.18%,0.11%和0.08%,土壤为森林涵养水源的主体。通过分析试验林土壤和凋落物持水能力发现,杉木+米老排+阴香+山杜英+枫香、杉木+火力楠+米老排+阴香+红荷和杉木+木荷+山杜英+香椿+山黄麻改造模式对土壤和凋落物持水能力影响效果较好,其水文功能较高。     

南方水稻黑条矮缩病毒P6抗体的制备及应用

为了建立快速准确检测田间介体白背飞虱带毒率的方法,利用Gateway 重组技术将与病毒早期复制有关的P6 基因的N端993 bp 构建原核表达载体pDEST17-P6,并将诱导表达的目的蛋白免疫注射新西兰大白兔制备多克隆抗体。结果表明：Western blot 检测制备的P6 抗体可特异性检测SRBSDV侵染水稻的P6 蛋白,免疫荧光标记技术可检测南方水稻黑条矮缩病毒(Southern rice black streaked dwarfvirus,SRBSDV)侵染白背飞虱体内的P6 蛋白,且P6 抗体可直观高效准确地用于免疫荧光标记检测昆虫带毒率。以上研究表明,所制备的P6 抗体可用于SRBSDV的田间介体昆虫带毒率快速检测,有助于病毒病害的监测和预报。