Obtaining species: sample size considerations

Suppose fish are to be sampled from a stream. A fisheries biologist might ask one of the following three questions: ‘How many fish do I need to catch in order to see all of the species?’, ‘How many fish do I need to catch in order to see all species whose relative frequency is more than 5%?’, or ‘How many fish do I need to catch in order to see a member from each of the species A, B, and C?’. This paper offers a practical solution to such questions by setting a target sample size designed to achieve desired results with known probability. We present three sample size methods, one we call ‘exact’ and the others approximate. Each method is derived under assumed multinomial sampling, and requires (at least approximate) independence of draws and (usually) a large population. The minimum information needed to compute one of the approximate methods is the estimated relative frequency of the rarest species of interest. Total number of species is not needed. Choice of a sample size method depends largely on available computer resources. One approximation (called the ‘Monte Carlo approximation’) gets within ±6 units of exact sample size, but usually requires 20–30 minutes of computer time to compute. The second approximation (called the ‘ratio approximation’) can be computed manually and has relative error under 5% when all species are desired, but can be as much as 50% or more too high when exact sample size is small. Statistically, this problem is an application of the ‘sequential occupancy problem’. Three examples are given which illustrate the calculations so that a reader not interested in technical details can apply our results.     

多效唑在鱼体内的分布,积累与类脂质含量相关性研究

实验水系统中，植物生长调节剂多效唑在鲤科类金鱼体内分布、积累的研究结果表明，＾３Ｈ－ＭＥＴ主要积累在鱼体消化系统；各器官／组织的积累量依次为：肠＞肝＞鳃＞皮＞肉＞骨；多效唑效生物积累因子（ＢＣＦ）和鱼体类脂质含量之间有较高的正相关性。     

城市生态系统中的生物资源保护

本文讨论了城市生态系统中的生物资源保护问题,论述了动物园、植物园及博物馆等在生物多样性保护方面所作的研部.作者并对今后需要进一步研究的课题提出了建议.     

沈阳市烟囱分布对大气污染的影响

本文介绍采用航空遥感技术和实地调查研究相结合的方法,分析了沈阳市烟囱数量、高度、密度以及高、中、低架烟囱的分布状况和特点,同时与大气污染监测结果对照分析了沈阳市煤烟型大气污染的规律及特点,研究了沈阳市烟囱分布对大气污染的影响。最后,提出了沈阳市燃煤污染的防治途径。     

入侵物种三裂叶蟛蜞菊挥发物的化感作用研究

对华南地区重要外来入侵物种三裂叶蟛蜞菊挥发物的化感作用进行了研究,以揭示该物种的入侵机制。采用水蒸气蒸馏法提取三裂叶蟛蜞菊地上部分的挥发油,提取率为2.58‰(质量比)。以稗草、三叶鬼针草和青葙3种杂草种子为供试对象,用种子萌发法测定了三裂叶蟛蜞菊挥发物的化感作用活性。结果表明:三裂叶蟛蜞菊的茎叶在密闭系统中产生的挥发性物质对稗草、三叶鬼针草和青葙的幼苗生长有显著抑制作用。稗草的根长、苗高和鲜质量分别比对照减少49.1%、35.0%和27.3%,三叶鬼针草的分别比对照减少18.8%、20.9%和28.6%,青葙的分别比对照减少62.9%、21.2%和50.0%。水蒸气蒸馏法所得的挥发油对稗草、三叶鬼针草和青葙的幼苗生长也有显著抑制作用,且抑制作用随着浓度的增大而增强。稗草的根长、苗高和鲜质量分别比对照减少88.2%、58.3%和45.5%,三叶鬼针草的根长、苗高和鲜质量分别比对照减少38.6%、34.5%和71.4%,青葙的根长、苗高和鲜质量分别比对照减少83.7%、51.5%和75.0%。结论:三裂叶蟛蜞挥发物具有化感作用,其作用机理值得深入研究。     

农村经济活动对云南野生稻居群的影响

云南野生稻包括普通野生稻(O.rufipogon Griff)、疣粒野生稻(O.meyeriana Baill)和药用野生稻(O.officinalis Wall),是属于全国仅存的几处宝贵基因资源库之一。野生稻具有许多优良特性及其相应的基因,在栽培稻育种和生物技术利用等方面具有巨大的潜力。文章在对云南野生稻居群长期调查或考察的基础上,分析了云南野生稻居群濒危的现状,认为热区经济开发、游牧、木材消耗、采集草药、外来种入侵和环境污染等农村经济活动是致濒的主要因素。阐明了选择合理的保护方法、加大普法和执法力度、完善保护体制与运行机制、调整种植结构是当前云南野生稻居群保护管理与经济协调发展的四项重点措施。     

厌氧发酵过程pH对微生物多样性和产物分布的影响

采用PCR-DGGE技术,研究了不同pH条件下蔬菜类有机垃圾厌氧发酵过程中的微生物多样性,探讨了微生物群落结构与发酵产物分布的关系.Shannon指数分析表明,pH=7和pH=8时的微生物多样性较高,随时间变化规律相似,而pH=5时的微生物多样性较低.UPGMA聚类分析和PCA分析结果也表明,pH=7和pH=8时的微生物群落结构相似,pH=5与之显著不同.在不同pH条件下的优势菌属都是乳酸细菌和梭菌。微生物多样性的变化与发酵产物分布具有一定相关性,pH通过影响微生物群落结构的变化最终影响发酵产物的分布.图4表2参27     

Model-based combination of spatial information for stream networks

Evolutionary improvements in Geographic Information Systems (GIS) now routinely allow the management and mapping of spatial-temporal information. In response, the development of statistical models to combine information of different types and spatial support is of vital importance to environmental science. In this paper we develop a hierarchical spatial statistical model for environmental indicators of stream and river systems in the United States Mid-Atlantic Region by combining information from separate monitoring surveys, available contextual information on hydrologic units and remote sensing information. These models are used to estimate the indicators throughout the riverine system based on information from multiple sources and aggregate scales. The analysis is based on information underlying the Landscape Atlas of the mid-Atlantic region produced by the US Environmental Monitoring and Assessment Program (EMAP). We also combine information from two overlapping separate monitoring surveys, the EMAP Stream and River Survey and the Maryland Biological Streams Survey. We present a general framework for comparative distributional analysis based on the concept of a relative spatial distribution. As an application, the spatial model is used to predict spatial distributions and relative spatial distributions for a watershed.     

京杭运河徐州段底栖动物与水质的关系

本研究利用生物监测方法，探明了京杭运河徐州段大型底栖无脊椎动物的生物种群及其分布。运用污染生物指数（Ｇｏｏｄｎｉｇｈｔ）和生物多样性指数（Ｓｈａｎｎｏｎ）统计表达，对京杭运河徐州段进行生物综合评价，同时，指出了该水体污染，将给徐州的两个地面饮用水厂及国家南水北调工程带来威胁和危险。通过生物指标与理化指标对比，综合分析研究，冲破了理化指标的限制，说明生物指标对水体污染的评价更全面、可靠而直观。     

广东省雾霾天气能见度的时空特征分析Ⅰ:季节变化

雾霾已经成为一种新的气象及环境灾害性现象,分析雾霾天气下低能见度的时空分布特征,对掌握雾霾的发生规律和减灾预报具有重要意义。文章利用1980—2003年广东省沿海地区26个地面气象观测站23年的气象观测资料,分析了广东省雾霾天气下能见度的时空分布特征。分析结果发现,1980—2003年广东地区雾霾天气下能见度的季节变化规律与雾天气时能见度的季节变化规律大体一致,即广东地区低能见度天气主要受雾天气的影响;另一方面,雾、霾天气时能见度的季节变化规律有很大不同,雾天气时能见度观测值在冬、春两季相对较高,最低值出现在3月份,最高值出现在9月份,其年变化表现为峰—谷型、稳定型和不规则波动型三种变化;霾天气时能见度的值在秋、冬两季相对较高,最低值出现在6月份,而且在5、6、7三个月中能见度值都很低;受广东沿海地形特征影响,雾天能见度的空间分布从西到东呈低—高—低—高的波列状分布,而霾天气时能见度的空间分布则没有明显的区域差异。