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51.
野生金头闭壳龟的资源现状调查 总被引:3,自引:1,他引:3
笔者于2001-2004年对金头闭壳龟(Cuoraaurocapitata)的野生种群的分布、数量及相关生态学进行了专项调查。结果表明,金头闭壳龟目前仅分布于青弋江源头和上游即北纬30°-30°52′的少数支流中,具体为安徽省泾县的古坝、蔡村和孤峰三地的山涧溪流以及黟县红星乡的清溪河流域。野外种群数量十分稀少,目前已不足400只。金头闭壳龟主要栖息在水质清澈、两侧植被茂密或一侧山脚多石缝的山涧溪流中。经对曾经发现过金头闭壳龟典型地带的各种生态指标的测量表明,泾县古坝乡沈村上沈村段的古坝河段的以及蔡村乡的东园至爱民段的丁溪河段,相比而言仍不失为金头闭壳龟较为理想的栖息地。 相似文献
52.
The impact of truncating data on the predictive ability for single‐step genomic best linear unbiased prediction 下载免费PDF全文
Jeremy T. Howard Tom A. Rathje Caitlyn E. Bruns Danielle F. Wilson‐Wells Stephen D. Kachman Matthew L. Spangler 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2018,135(4):251-262
Simulated and swine industry data sets were utilized to assess the impact of removing older data on the predictive ability of selection candidate estimated breeding values (EBV) when using single‐step genomic best linear unbiased prediction (ssGBLUP). Simulated data included thirty replicates designed to mimic the structure of swine data sets. For the simulated data, varying amounts of data were truncated based on the number of ancestral generations back from the selection candidates. The swine data sets consisted of phenotypic and genotypic records for three traits across two breeds on animals born from 2003 to 2017. Phenotypes and genotypes were iteratively removed 1 year at a time based on the year an animal was born. For the swine data sets, correlations between corrected phenotypes (Cp) and EBV were used to evaluate the predictive ability on young animals born in 2016–2017. In the simulated data set, keeping data two generations back or greater resulted in no statistical difference (p‐value > 0.05) in the reduction in the true breeding value at generation 15 compared to utilizing all available data. Across swine data sets, removing phenotypes from animals born prior to 2011 resulted in a negligible or a slight numerical increase in the correlation between Cp and EBV. Truncating data is a method to alleviate computational issues without negatively impacting the predictive ability of selection candidate EBV. 相似文献
53.
以不同发情周期雌性绵羊子宫、输卵管为研究对象,采用免疫组织化学技术,针对血管内皮生长因子(VEGF)在绵羊子宫、输卵管的表达、定位和变化规律进行了检测,同时应用相关图像分析软件对抗原染色强度进行了定量分析。结果表明:输卵管在发情0~15d,VEGF表达量在第9天达到峰值后经历波动逐渐下降过程,输卵管内膜上皮细胞是VEGF抗原的主要靶细胞;而子宫角在发情0~15d,VEGF表达量在第5天达到峰值后经历波动逐渐下降过程,子宫内膜固有层及腺体周围细胞为VEGF抗原的主要靶细胞。该研究结果为绵羊生产中进一步提高受胎率和妊娠率及频密产羔等技术的应用提供了科学依据。 相似文献
54.
Within this paper we describe an unmanned aerial vehicle (UAV) based method to estimate the spatial feed pellet distribution in salmon fish-cages and exploit it within a case study to determine the radial pellet distribution for different rotor spreaders and blower configurations. Compared to previously used methods, capturing pellets thrown from a rotary feed spreader in rows of Styrofoam boxes, the UAV based method is simpler and faster to setup and allows to cover a larger portion of the sea cage surface area. We compare results obtained with the Styrofoam box method with results we obtained by an automatic analysis of aerial videos taken by the UAV during feeding experiments. The employed method helps to gain insight into the spatial feed pellet distribution in full-scale salmon fish-cages where the feeding pipe and actual fixation of the spreader may influence the dynamic behaviour of the feeding system. This can also be seen as a step towards a continuous measuring of the feed pellet distribution, particularly in view of possible future feeding systems that may allow to adapt the feed pellet distribution to the actual fish distribution. 相似文献
55.
为了探寻安徽省农业气象灾害的分布特点以及各种气象灾害对粮食生产的影响,本研究基于安徽省1992—2012年有关气象灾害数据,对4种主要气象灾害(旱灾、水灾、风雹灾、霜冻灾)的分布特征进行统计分析,并采用灰色关联分析研究其对安徽省粮食单产的影响。结果表明:1992—2012年,安徽省气象灾害具有发生频率高、波动大的特点,但整体上呈下降趋势。旱灾和水灾是发生面积较大的气象灾害,且常在时间上交织、空间上并存。灰色关联分析表明,4种气象灾害对粮食产量影响顺序:风雹灾水灾旱灾霜冻灾,说明风雹灾是影响粮食产量最主要的气象灾害,其次是水灾、旱灾,霜冻灾影响较小。本研究可为安徽省防灾减灾措施的制定提供决策依据。 相似文献
56.
科学认识乡村地域结构是全面推进农业农村现代化和乡村振兴的基础。本文以扶余市第二次土地调查调数据为基础,借助ArcGIS空间分析软件,运用规模分析、核密度估算、缓冲区分析,从用地规模、分布格局与土地利用条件方面探讨扶余市农村居民点地域分异特征。研究表明:扶余市以微、小型居民点居多,居民点数量随着规模的增大逐渐减少,居民点之间的距离差异较大,总体呈现大散居、小聚居,不均匀分散分布;农村居民点的平均核密度为0.4个/km2,空间布局呈东南部高密度集聚成片,向西逐渐密度降低,西部零散错落分布;居民点分布呈现较强的城镇指向性,交通用地对居民点有集聚的作用,河流对微型居民点和大型居民点有集聚吸引的功能。 相似文献
57.
基于马尔科夫链蒙特卡洛(简记为MCMC)模拟的参数贝叶斯估计,对改进的广义帕累托分布(简记为MGPD)模型进行了优化,并利用该模型得到了地质灾害损失的在险损失值(简记为VaR)和条件损失值(简记为CVaR).以湖南娄底市地质灾害损失数据进行实证分析及模型适应性检验,结果表明:优化后的模型不仅具有很好的极值数据描述能力,而且具有较强的适用性. 相似文献
58.
本文着重分析了当前我国图书出版发行环境中出现的一些新的变化、新的特点和新的问题,并提出了在图书馆采访工作中,针对这些问题可采取相应的措施。 相似文献
59.
Many studies showed that permafrost has profound influence on alpine ecosystem. However, former researches were mainly focused on typical points by temporal scales. There were few studies about the correlation between vegetation characteristics and different altitudes covering a large region in spatial pattern, especially in transitional permafrost(TP). There were continuous permafrost(CP) discontinuous permafrost(DCP) and seasonal frozen ground(SFG) in this study region. The types of permafrost changed from SFG to DCP, and finally become CP as the altitudes of Xidatan increase. In this paper, 112 845 points interpreted by HJ1-B(environment and disaster monitoring and prediction small satellite constellation), vegetation investigation points, thawing layer thickness research sites, ground temperature and water content observation plots were used to examine the spatial pattern of vegetation which were located in different altitudes in Xidatan, a typical TP region, in Qinghai-Tibetan Plateau. Vegetation characteristics, soil moisture content(SMC) and thaw depths were collected in 15 August to 25 August2012. Characteristics of vegetation were mainly represented by fractional vegetation cover(FVC) derived from the normalized difference vegetation index(NDVI), as well as above ground biomass(AGB). In this paper, we analyzed that the distinction of vegetation characteristics in each range through statistics data. These ranges were divided by varied altitudes. For examples, the ranges were divided into 50 m or 100 m. In this study we use a large area plots method to further discuss the relationship between the features of vegetation and the different regions of permafrost based on altitudes shifts in Xidatan. A diagram described the vegetation characteristics variability with rising altitudes in transitional permafrost region was drawn in this paper. Our results illustrated the FVCs first increased in SFG region and then decreased in DCP zone slowly, and in CP region FVCs soared then dropped dramatically. With the altitudes increased, the curve of FVCs indicated a parabolic distribution except a little difference in the first 200 m range. 相似文献
60.