Polymorphic mountain whitefish (Prosopium williamsoni) in a coastal riverscape: size class assemblages,distribution, and habitat associations

We compared the assemblage structure, spatial distributions, and habitat associations of mountain whitefish (Prosopium williamsoni) morphotypes and size classes. We hypothesised that morphotypes would have different spatial distributions and would be associated with different habitat features based on feeding behaviour and diet. Spatially continuous sampling was conducted over a broad extent (29 km) in the Calawah River, WA (USA). Whitefish were enumerated via snorkelling in three size classes: small (10–29 cm), medium (30–49 cm), and large (≥50 cm). We identified morphotypes based on head and snout morphology: a pinocchio form that had an elongated snout and a normal form with a blunted snout. Large size classes of both morphotypes were distributed downstream of small and medium size classes, and normal whitefish were distributed downstream of pinocchio whitefish. Ordination of whitefish assemblages with nonmetric multidimensional scaling revealed that normal whitefish size classes were associated with higher gradient and depth, whereas pinocchio whitefish size classes were positively associated with pool area, distance upstream, and depth. Reach‐scale generalised additive models indicated that normal whitefish relative density was associated with larger substrate size in downstream reaches (R² = 0.64), and pinocchio whitefish were associated with greater stream depth in the reaches farther upstream (R² = 0.87). These results suggest broad‐scale spatial segregation (1–10 km), particularly between larger and more phenotypically extreme individuals. These results provide the first perspective on spatial distributions and habitat relationships of polymorphic mountain whitefish.     

湘西北长果安息香种群数量与分布格局

对湖南石门壶瓶山景关门、桑植龙潭坪茅垭村样地的长果安息香(Changiostyrax raxdolichocarpa)种群数量和分布格局进行调查和分析。结果表明：长果安息香种群的年龄结构呈衰退型，个体数量主要集中在小树(IV龄段)，幼龄级株数和老龄级株数匮乏；长果安息香种群在进入生理死亡年龄前有2个死亡高峰，第1个峰值产生于幼树(II、III龄段)，主要原因是种内和种间竞争(主要是光照)，第2个峰值产生于中树长成大树阶段(V、VI龄段)，除种内、种间对环境的竞争外，生长地土层浅薄、大树倒伏及人为砍伐亦加剧了该峰值的产生；种群整体呈聚集分布类型，小树向中树、大树变化过程表现出聚集分布向随机分布转变，导致长果安息香濒危的主要原因是种子萌发率极低、种群竞争能力较差以及人为干扰等。     

论韶关地区道路绿化植物的科学选择与配置

韶关地区道路绿化树种大多数是从南部珠三角地区和北部湖南地区引进，可能存在所引进树种是否适应韶关气候的问题。因此，如何运用科学的方法选择与配置道路绿化植物和确定合适的种植位置就成为道路绿化工程的关键。     

关于地理空间数据整合与持续高效更新存在的问题分析

文章针对当前地理空间数据整合与持续高效更新所存在的问题,在地理空间数据更新中引入了“数据同化”这一思想和概念,对持续高效更新存在的问题及“地理空间数据同化”的涵义和关键技术进行了论述.     

农民专业合作社的融资问题分析——以湖南省60家农民专业合作社为例

发展农民专业合作社是促进“三农”发展的重要途径之一,而长期以来融资问题成为了农民专业合作社发展的瓶颈.该研究基于农民专业合作社融资现状,对农民专业合作社融资困难的内外部原因进行了剖析,并提出加强农民专业合作社自身建设,加快农业基础设施建设,转变政府扶持方式,健全农业保险制度,完善土地使用权抵押制度等促进农民专业合作社改良性发展的对策建议.     

甘肃黄河三峡景区旅游资源空间结构研究

旅游空间结构是旅游系统功能组织方式在空间上的投影或表象,其空间结构是否合理直接影响到旅游目的地旅游业的发展态势。黄河三峡景区凭借其丰富、独特的资源优势,已成为黄河流域最著名的景区之一。受河谷地带的基础性影响,其资源类型、空间结构、游览线路等表现出典型的空间特征,深刻影响着景区旅游空间格局。借助Arc GIS空间网络分析模块和Excel平台,对黄河三峡景区旅游资源空间结构进行定量分析,发现旅游资源空间分布呈集聚态势,基尼系数高达0.755,分布均匀度仅为0.245;采用最邻近指数和Voronoi多边形的变异系数分析空间分布类型;用地理集中指数和基尼系数分析空间分布均衡性,运用β指数、γ指数和α指数刻画空间连接度。结果表明:景区内旅游资源的空间分布均匀度低,呈多中心集聚分布。这既有利于景区内各景点之间的整合和旅游规模效应的产生,又可以减弱区间屏蔽作用等外部不经济性。景区内各景点之间的交通网络密度低,空间联系较弱,通达性较低。各景点之间的直接连接较少,旅游路线多为单线往返,缺少串联各个景点的环形线路。     

Hull-White利率模型仿真与债券估值

由于“中”“庸”两词语义上的模糊性，其哲学含义颇为复杂。从郑玄到二程、吕祖谦，尤其是朱熹，都对“中庸”进行了解释，现代学者对《中庸》书名的释义更是多种多样。对于《中庸》的时代以及与子思的关系问题，中国历代学者以及西方的汉学家都提出了不同的观点，至今仍然莫衷一是。     

4种种植体系的水肥利用状况和经济效益比较

为了筛选适宜曲周县后老营村农业生产的较优种植体系并设计更好的种植体系,采用随机抽样调查的方法,对该村主要作物的种植体系及其水肥资源利用状况和经济效益进行了详细调查。结果表明:棉花-西瓜套作体系的水肥资源利用率最高,小麦-西瓜-玉米间套作体系的经济效益最好,棉花-西瓜套作体系次之,二者差异不显著。未来可以基于这2种种植体系重新设计新的种植体系,从而在生态、经济、环境等方面取得较好的综合效益。     

财税政策对河北省农业保险的支持分析

农业保险是为了减少农业生产的风险、降低自然灾害给农业造成的损失而出现的一项保险制度,需要财政税收政策的支持来为其保驾护航。河北省目前已经针对农业保险采取了一系列措施以促进其发展,但是与西方发达国家相比,还存在一定差距。分析了河北省农业保险的财税政策支持,并针对该省农业保险存在的问题提出对策及建议。     

Reconstructing mole tunnels using frequency-domain ground penetrating radar

The European mole (Talpa europaea L.) inhabits an underground tunnel system whereby the density, extent and condition of the subsurface tunnels are indicative of its activity. Currently, no survey method was able to reveal the spatial extent and condition of the mole's tunnel network. Frequency-domain ground penetrating radar (GPR) was evaluated on its potential to image these shallow tunnel systems. This technique allows for a non-invasive, high-resolution mapping of the subsurface. We examined the effectiveness of this GPR system for delineating the mole's tunnel network. The integration of different depth slices allowed a detailed overview of the tunnel system. Automatic feature recognition on these GPR images was proven valuable for the detection and representation of the mole tunnels. The GPR survey proved successful in mapping the mole's tunnel network, which facilitates the interpretation and characterization of the mole's living environment. This can be linked to the occurrence of earthworms, as the principle food source of the moles, which regulate important ecosystem processes within the soil. This offers new perspectives for the understanding of the mole's habitat.