警惕酒椰象甲的入侵

2015年8月,深圳出入境检验检疫局从来自香港的旅客携带物中截获大量酒椰棕榈果,深圳局实验室利用声测仪从该果中截获酒椰象甲(Leurostethus raphiae Marshall,1945),同期,北京出入境检验检疫局从非洲入境旅客携带的酒椰棕榈果中检出该虫。酒椰象甲为中国口岸首次截获。本文对该种有害生物的分类地位、分布、寄主、形态特征、传播途径等进行了介绍,并介绍了一种新型的检测技术-声测仪,提出了口岸检疫的应对措施。     

绿道思想在绿地系统规划中的体现——以余江县城市绿地系统规划为例

笔者阐述了国内外绿道的发展历程、实践经验、绿道的基本理论,认为绿道建设的实质就是以廊道为纽带,联系分散孤立的斑块,形成"点-线-面"结合的自然生态体系。绿道可分为区域绿道、城市绿道和社区绿道,主要由自然因素所构成的绿廊系统和为满足绿道游憩功能所配建的人工系统两大部分构成。在此基础上,结合余江县绿地系统的现状,分析了现状资源和绿道规划原则,强调充分利用现有的水系和绿地资源优势,规划建立余江县县域和中心城区绿道网络,发挥绿道的生态、游憩和文化观光等综合功能。     

温度对尖锥额野螟卵和幼虫生长发育的影响

为探讨尖锥额野螟卵和幼虫生长发育和温度之间的关系,在室内利用人工气候箱,分别对17,21,25,29,33℃条件下卵及各龄幼虫的发育历期、发育速率、发育起点温度和有效积温及幼虫存活率进行了研究。结果表明:尖锥额野螟在17~33℃的温度范围内,卵及各龄幼虫的发育历期均随温度的升高而缩短,发育速率随温度升高而加快,采用线性回归模型和Logistic模型对卵及各龄幼虫的发育速率进行模拟分析,两种模型均能较好地反映出环境温度与卵及各龄幼虫发育速度的关系。温度对尖锥额野螟各龄幼虫存活率有一定影响,33℃高温下其存活率显著低于其他温度处理,不利于尖锥额野螟幼虫的生长发育。综合各温度下幼虫发育历期和存活率,其适宜环境温度应为25~29℃。尖锥额野螟卵的发育起点温度为9.82℃,有效积温为63.54℃·d,幼虫的发育起点温度为8.89℃,有效积温为276.50℃·d。     

璧山县土壤侵蚀特征及影响因子研究

在ArcG IS平台下,利用璧山县2001年DEM图、土地利用现状图和土壤侵蚀等级图等数据源,对研究区土壤侵蚀在不同坡度、不同海拔和不同土地利用方式下的分布特征进行了研究。结果表明:6°—15°坡度是各级侵蚀发生最多的地带;200—400 m海拔梯度是各级侵蚀发生的主要地带;耕地是导致土壤侵蚀的主要土地利用方式。针对璧山县实际,提出了加强水土保持生态建设的建议。     

Reduced effective population size in an overexploited population of the Nile crocodile (Crocodylus niloticus)

Unchecked exploitation of wildlife resources is one of the major factors influencing species persistence throughout the world today. A significant consequence of exploitation is the increasing rate at which genetic diversity is lost as populations decline. Recent studies suggest that life history traits affecting population growth, particularly in long-lived species, may act to moderate the impact of population decline on genetic variation and lead to remnant populations that appear genetically diverse despite having passed through substantial demographic bottlenecks. In this study we show that the retention of genetic variation in a partially recovered population of Nile crocodile is deceptive, as it masks the reality of a significant decline in the population’s effective size (N_e). Repeated episodes of unchecked hunting in the mid to late 20th century have today led to a five-fold decrease in the population’s N_e. Using current census data we estimate the contemporary N_e/N ratio as 0.05 and, in light of quotas that permit the ongoing removal of adults, simulated the likely effects of genetic drift on extant levels of variation. Results indicate that even if the current effective size is maintained, both allelic diversity and heterozygosity will decline. Our findings have complex implications for long-lived species; an emphasis on the retention of genetic variation alone, whilst disregarding the effects of population decline on effective size, may ultimately obscure the continued decline and extinction of exploited populations.     

Laboratory evaluation of a model for soil crumbling for prediction of the optimum soil water content for tillage

A model for soil crumbling, called the capillary crumbling model (CCM) was introduced by Aluko and Koolen [Aluko, O.B., Koolen, A.J., 2000. The essential mechanics of capillary crumbling of structured agricultural soils. Soil Till. Res. 55, 117–126]. According to the CCM, the optimum soil water content for tillage (θ_OPT) may be defined as the water content at which the capillary bonding strength between aggregates is minimum. The objective of this study was to evaluate the CCM for the arable layer of 10 agricultural soils (sandy loam to clay textures) from semi-arid regions in western Iran. The results were compared with conventional soil workability limits such as 0.85 of the soil plastic limit (0.85θ_PL), Proctor critical water content (θ_Proctor), 0.6 or 0.7 of water content at matric suction of 50 hPa (0.6–0.7θ_50 hPa), and the Kretschmer optimum water content (θ_Kretschmer = θ_PL − 0.15(θ_LL − θ_PL)) where θ_LL is the soil liquid limit. Repacked soil cores were prepared from intact soil aggregates (0.50–4.75 mm) to 0.9 of the critical bulk density (to represent the soil conditions before tillage). Tensile strength and matric suction of the cores were determined at different soil water contents obtained by slow drying. The CCM provided evidence for the physics and mechanics of crumbling in the studied soils. It revealed that effective stresses are the dominant inter-aggregates forces, at least for the wet range of soil water content. A fall in strength of inter-aggregate bonds (i.e. tensile strength) was recorded due to water emptying from structural pores in a narrow range of matric suction (h_OPT) which was consistent with the model. With increasing soil organic matter and clay contents the fall became more distinct, indicating increased structural stability. The θ_OPT values determined by the CCM were found in the h_OPT range 551–612 hPa corresponding to 0.91–0.79θ_PL, which was in agreement with published values for the soil workability limit. Negative correlations between h_OPT and clay and organic matter contents clearly confirmed the increasing effect of soil structure on the enlargement of inter-aggregate pores. High correlations were observed between θ_OPT and 0.85θ_PL, θ_Proctor or 0.7θ_50 hPa. The results showed that the CCM might be recommended as a physically based method for the determination of θ_OPT. Considering the 1:1 relationships between θ_OPT and 0.85θ_PL or θ_Proctor, and easy determination of θ_PL and θ_Proctor, use of these indices is recommended in situations where the CCM is not applicable.     

Breeding programme for Piétrain pigs in Bavaria with an estimation of genetic trends and effective population size

Population structure, performance testing and breeding scheme of the sire breed Piétrain in Bavaria were analyzed as a basis for further optimization studies of the breeding programme. To evaluate the current breeding programme, genetic trends and effective population size were estimated. Four data sets were used which contained breeding animals born between 1981 and 2005, estimated breeding values of traits in the breeding goal, records from young boars in field test and records from purebred and crossbred progeny on test stations. The population is subdivided in many small herds. That has disadvantages with respect to a uniform breeding goal used across herds and with respect to selection intensity and the avoidance of inbreeding. The idealized selection practice consists of three selection stages. On the first two stages information from half and full sibs on test stations is most important so that the risk of co-selecting related animals is increased. The breeding scheme is a mixture of a half sib design and a progeny testing design, but both have disadvantages. Nevertheless, genetic trends are in the desired directions. To improve accuracy and intensity of selection, only AI-boars should be used instead of natural service sires. Though the effective population size is high, the recent trend of inbreeding shows that the extensive use of popular AI-boars can lead to a rapid increase of inbreeding.     

栗蚕卵发育起点温度和有效积温的测定

栗蚕(Dictypoea japonica)是珍贵的野生泌丝昆虫资源。对解除滞育的栗蚕卵分别通过15、18、21、24℃恒温处理暖种,测定栗蚕卵的发育起点温度为(10.2±0.6)℃、孵化有效积温为(181.7±11.6)℃.d,表明一旦给予越冬后解除滞育的栗蚕卵9.6℃以上的温度条件,就可能使其开始发育,当有效积温达到170℃.d时便可孵化。该结果可作为栗蚕卵的人工越冬保护及暖种技术处理的理论依据之一。     

低聚糖体外促进肠道有益菌增殖的研究

本文通过测定低聚糖对肠道有益菌的体外增殖促进效果,研究低聚糖对肠道有益菌的增殖影响作用。结果表明：低聚果糖和低聚异麦芽糖对双歧杆菌、乳酸杆菌均有显著的增殖促进作用,说明这些菌株能够利用低聚糖。     

黄河流域泥沙配置状况及其资源化

 通过分析黄河流域水沙运动过程和水沙分布特点,给出了流域泥沙配置单元,指出流域泥沙配置单元的配置量随着流域治理工程实施、径流条件等不断变化;1950—1999年,流域水土保持滞沙、水库拦沙、河道滞沙、两岸引沙用沙、河口淤积与入海泥沙等配置单元年均配置沙量占流域产沙量(17.63亿t)的14.24%、14.05%、12.19%、10.56%和50.77%;阐述了水库拦沙多、河道淤积严重是黄河流域泥沙配置现状不合理的主要原因,指出流域水沙资源优化配置和泥沙资源化是维护黄河健康的重要途径;结合黄河下游长期泥沙处理与利用的经验和教训,总结了黄河下游泥沙资源化的主要途径,包括淤临淤背、河道治理与河槽维护、引洪淤灌与土壤改良、灌区堆沙高地农田化、建筑材料转化、河口泥沙造地和疏浚泥沙利用、湿地塑造等。