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1.
邹惠渝和张凤春两位先生所撰写的"长苞铁杉和铁杉属数量分类的研究"一文(见<南京林业大学学报>,1996,20(1)43~47),至少存在以下3个问题值得商榷一是取材欠完整,二是聚类方法单一,三是结合线计算错误.据本文重新核算,<邹文>的结论有误.  相似文献   

2.
 The abundance and biomass of Corophium multisetosum Stock, 1952 were determined from benthic corer samples collected monthly over 1 yr in the upper reaches of Canal de Mira (Ria de Aveiro, Portugal). Both density and biomass over the sampling period were negatively correlated with water temperature and positively correlated with chlorophyll a concentration in the sediment. C. multisetosum density was significantly negatively correlated with plant biomass and positively correlated with salinity. The nature of the sediment, favourable environmental conditions, high availability of food and low interspecific competition allowed the population to reach a maximal density of 200 × 103 individuals m−2 and a maximal biomass (ash-free dry wt, AFDW) of 62 gAFDW m−2. The population was highly productive, especially during the autumn/winter period. Production, estimated by two different methods (Hynes method: 251 gAFDW m−2 yr−1; Morin–Bourassa method: 308 gDW m−2 yr−1), was much higher than the values reported for other Corophium species. The annual P:Bˉ ratio (10) was high, but similar to values reported for Swedish populations of C. volutator and lower than the values estimated from Mediterranean populations of C. insidiosum. Received: 8 October 1999 / Accepted: 22 June 2000  相似文献   

3.
The growth rates of two fish species, the winter flounder Pseudopleuronectes americanus (Walbaum) (19.3 to 42.6 mm total length, TL) and the tautog Tautogaonitis (Linnaeus) (23.9 to 55.9 mm TL), were used to evaluate habitat quality under and around municipal piers in the Hudson River estuary, USA. Growth rates were measured in a series of 10 d field caging-experiments conducted at two large piers in the summers of 1996 and 1997. Cages (0.64 m2) were deployed along␣transects that stretched from underneath the piers to beyond them, encompassing the pier edge (the transitional zone between the pier interior and the outside). Growth in weight (G w ) was determined at five locations along the transect, 40 m beneath the pier, 20 m beneath the pier, at the pier edge, 20 m beyond the pier edge, and 40 m beyond. Under piers, mean growth rates of winter flounder and tautogs were negative (xˉG W  = −0.02 d−1), and rates were comparable to laboratory-starved control fishes (xˉG W  = −0.02 d−1). In contrast, mean growth rates at pier edges and in open waters beyond piers were generally positive (xˉG W ranged from −0.001 to +0.05 d−1), with growth at pier edges often being more variable and less rapid than at open-water sites. Analyses of stomach contents upon retrieval of caged fishes revealed that dry weights of food were generally higher among fishes caged at open-water stations ( range = 0.02 to 0.72 mg dry wt) than at pier-edge ( range = 0.01 to 0.54 mg) or under-pier ( range = 0.03 to 0.11 mg) stations, although it was apparent that benthic prey were available at all stations on the transect. Our results indicate poor feeding conditions among fishes caged under piers, and suboptimal foraging among fishes caged at pier edges. Inadequate growth rates can lead to higher rates of mortality, and, based on these and other earlier experiments, we conclude that under-pier environments are poor-quality habitats for some species of juvenile fishes. Received: 12 March 1998 / Accepted: 9 November 1998  相似文献   

4.
Atmospheric mercury emissions from polluted gold mining areas (Venezuela)   总被引:1,自引:0,他引:1  
Soil, waste rock and mud from mercury-gold amalgamation mining areas of El Callao (Venezuela) are highly enriched in Hg (0.5–500 μg g−1) relative to natural background concentrations (<0.1 μg g−1). Mercury fluxes to the atmosphere from twelve polluted sites of this area were measured in situ (6 a.m. to 8 p.m.) using a Plexiglas flux chamber connected to a portable mercury analyzer (model RA-915+; Lumex, St. Petersburg, Russia). Mercury fluxes ranged between 0.65 and 420.1 μg m−2 h−1, and the average flux range during the diurnal hours␣was 9.1–239.2 μg m−2 h−1. These flux values are five orders of magnitude higher than both reported world background Hg fluxes (1–69 ng m−2 h−1) and the regional values, which are in the range 2–10 ng m−2 h−1. The flux results obtained in this study are, however, similar to those measured at Hg polluted sites such as chloro-alkali plants or polymetallic ore mining districts (>100,000 ng m−2 h−1). The results from this study also show that Hg emissions from the soil are influenced by solar radiation, soil temperature and soil Hg concentration. Our data suggest that solar radiation may be the dominant factor affecting Hg° emission since the major species of mercury in polluted soil is Hg° (85–97% of total Hg). The simple release of Hg° vapor is probably the dominant process occurring with incident light in the field. The apparent activation energy for mercury emission indicates that the volatilization of mercury mainly occurred as a result of the vaporization of elemental mercury in soil. The degree of Hg emission differed significantly among the soil sites studied, which may be due to variations in soil texture, organic matter content and soil compaction.  相似文献   

5.
以89个植物群落调查样地数据为基础,运用8个多样性指数对山西关帝山神尾沟物种多样性与环境之间的关系进行了分析.(1)群落总的表现为多样性和均匀度随海拔升高而下降,丰富度从1700m下降到2400m后开始升高;(2)群落不同层次表现为乔木层和灌木层多样性、丰富度和均匀度随海拔升高而下降,草本多样性和均匀度表现为上升趋势,丰富度下降到1900m后开始上升;(3)乔灌草三者多样性和丰富度指数值以及变化幅度都表现为草本层>灌木层>乔木层,三者均匀度相差不大;(4)群落不同坡向表现为阳坡多样性和丰富度都大于阴坡,均匀度相差不大.图6参7  相似文献   

6.
33 a生福建柏人工林群落能量的研究   总被引:7,自引:0,他引:7  
在福建三明对33 a生福建柏和杉木群落能量的研究结果表明福建柏群落和杉木群落干重热值和去灰分热值均以树叶最高,最低的为草本叶和茎或草本根;两个群落不同层次干重热值和去灰分热值的大小均为乔木层>林褥层>灌木层>草本层;两个群落乔木层干重热值和去灰分热值均以干皮最低. 两个群落不同组分灰分含量差异悬殊,最高的均为草本叶和茎,最低的均为干材. 福建柏的干重热值、去灰分热值、灰分含量均高于杉木,表明福建柏生成单位重量生物量的能量耗费比杉木多. 福建柏群落的能量现存量、年净增量、年归还量(通过凋落物)、年净固定量分别是杉木群落的0.97倍、1.65倍、1.15倍和1.36倍. 福建柏群落的太阳能转化效率为1.42%,而杉木群落为1.04%. 林下植被虽然能量现存量仅占群落的很小一部分,但在能量流动中占有重要地位,林下植被的能量流动速率比乔木层大得多,这对维持和提高地力较为有利. 33 a生福建柏群落仍然具有较大的能量年净增量,轮伐期应比杉木长;具有较高的能量流动速率,地力维护的能力也较强,是优良的造林树种. 福建柏经营密度应适当降低,发育群落林下植被以改良地力. 表5 参12  相似文献   

7.
The extensive extraction of arsenic (As)-contaminated groundwaters for drinking, household and agricultural purposes represents a serious health concern in many districts of Bangladesh. This laboratory-based incubation study investigated the sources and mechanisms of As mobilization in these groundwaters. Several incubation studies were carried out using sediments collected from the Bangladesh aquifer that were supplemented, or not, with different nutrients, followed by an analysis of the sediment suspensions for pH, ORP (oxidation-reduction potential), EC (electrical conductivity) and As and Fe(ΙΙ) concentrations. In the substrate-amended sediment suspensions incubated under anaerobic environment, there was a mobilization of As (maximum: 50–67 μg/l) and Fe(ΙΙ) (maximum: 182 μg/l), while the ORP value decreased immediately and drastically (as much as −468 mV to −560 mV) within 5–6 days. In the sediment suspensions incubated under control and aerobic conditions, no significant As mobilization occurred. The simultaneous mobilization of As and Fe(ΙΙ) from sediments is a strong indication that their mobilization resulted from the reduction of Fe oxyhydroxide by the enhanced activity of indigenous bacteria present in the sediments; this phenomenon also provides insights on the mobilization mechanism of As in groundwater. The concentrations of As in the sediments used in the incubation studies were strongly linked to the gradients of redox potential development that was stimulated by the quantity of organic nutrient (glucose) used. The penetration of surface-derived organic matter into the shallow aquifer may stimulate the activity of microbial communities, thereby leading to a reduction of iron oxyhydroxide and As release.  相似文献   

8.
杭州市空气中PM10的化学组成特征   总被引:2,自引:0,他引:2  
于2001年2月至2002年4月在杭州5个空气质量自动监测子站采集了176组PM10样品,分析了22种化学元素、5种离子以及有机碳(OC)和元素碳(EC)的含量,并讨论了PM10的化学组成特征.杭州市空气中铅污染仍然存在,硫的存在形式主要为水溶性硫酸盐.5种水溶性离子的浓度由大到小排列的顺序是SO2-4> NO-3> NH+4>Cl->F-,大气中NH+4主要是以(NH4)2SO4,NH4HSO4和NH4NO3的形式存在.OC和EC浓度分别为20.4 μg·m-3和4.0 μg·m-3,其相关性不好表明碳的来源复杂.PM10的物质平衡计算表明,局地地质尘是最高的化学组分,达27.7%,其次为有机物23.9%,第三为硫酸盐16.2%,这3个组分占PM10的67.8%,其它为硝酸盐6.3%,铵盐6.1%,微量元素5.5%,元素碳3.4%以及未测组分11.0%.  相似文献   

9.
徐明岗 《生态环境》2001,10(2):111-114
对不同浓度KCl和不同pH下,3种可变电荷土壤和4种恒电荷土壤Cl-吸附量进行了测定。结果表明,土壤Cl-吸附量随平衡Cl-浓度C(e)增加而增大,恒电荷土壤呈线性,可变电荷土壤在添加Cl-0.5~5.0mmol/L下,符合Langmuir吸附等温式。同一浓度下的Cl-吸附量及其随浓度增加的速率均为砖红壤>红壤>赤红壤>黄棕壤>棕壤、暗棕壤和黑土,与这些土壤所带正电荷量顺序相一致。Langmuir方程K值较小且几种土壤差异不大。恒电荷土壤对Cl-的吸附量很小,在浓度较低时常出现负吸附,其吸附机理可能更多的是与K+吸附时的同时吸附。7种土壤Cl-吸附量均随pH增加而降低,但降低强度可变电荷土壤远大于恒电荷土壤。  相似文献   

10.
研究了鄂南红壤区不同种植模式的旱地及坡荒地、不同轮作模式的水田、水田改旱菜地的土壤养分状况。本区土壤有机质含量和氮素含量较低,磷素普遍缺乏,钾素含量较低且呈下降趋势。土壤有机质及氮含量呈现水田类>水田改旱地类>旱地类;土壤磷含量则是水田改旱地类>水田类>旱地类;水田类钾含量明显低于旱地类和水田改旱地类,而且三熟制油菜-西瓜-晚稻种植模式下,土壤全钾及速效钾含量呈下降趋势。水田改为旱作是改善土壤水分状况的有效措施。  相似文献   

11.
随着改革开放的深入和市场经济的发展,公民社会正在我国逐渐兴起.与此相应,传统的泛政治化的德育也须进行相应的转变,从单纯的政治教育向多样化的公民教育发展,从单向灌输向多渠道的疏导发展,从封闭教育向开放教育发展,从过高的理想目标向注重现实道德的践履发展,从强调绝对服从向培养公民的独立自主人格和平等自由观念发展.  相似文献   

12.
Despite increasing support for conservation globally, controversy over specific conservation policies persists among diverse stakeholders. Investigating the links between morals in relation to conservation can help increase understanding about why humans support or oppose policy, especially related to human–wildlife conflict or human conflict over wildlife. Yet the moral dimension of human–wildlife conflict has mostly gone unconsidered and unmeasured; thus, policy and programmatic efforts to reduce controversy may be missing a key part of the equation. We conducted a web‐based survey (n = 1239 respondents) in Michigan (U.S.A.) to investigate cognitive and emotional influences on the value–behavior relationship. Respondents were identified by their interest and involvement in Michigan wolf management. The survey consisted of questions about values, emotions, cognitions, and behaviors relative to wolves in Michigan. We used path analysis to explore whether emotions and cognitions mediated the relationship between value and behavior. Most respondents attributed intrinsic value to wolves (n = 734) and all life (n = 773) and engaged in behaviors that benefited wolf populations and ecosystems regardless of stakeholder group (e.g., environmentalist, farmer). Attributing intrinsic value to wolves was positively related to favorable emotions toward wolves and cognitive assessments that hunting and trapping of wolves is unacceptable. Despite similarities in attribution of intrinsic value, groups differed in emotions and cognitions about wolf hunting. These differences provide a useful way to predict stakeholder behavior. Our findings may inform interventions aimed at increasing support for wolf management policies and positive interactions among stakeholders and wildlife. Leveraging agreement over intrinsic value may foster cooperation among stakeholders and garner support for controversial conservation policy.  相似文献   

13.
思想道德修养课是对大学生进行思想政治教育的主渠道之一.本文就如何切实提高思想道德修养课的教学质量,不断增加其育人效果、提出进行教学改革,具体方法是:思路树立课堂教学新模式,在教学中做到既教书又育人,进行课堂教学方法改革.  相似文献   

14.
由于课程的特殊地位,德育课教学应紧紧围绕学生,化抽象为具体,化深奥为浅显,化枯燥为生动,以激发学生学习的兴趣,提高教学效果.幽默是增强课堂感召力、说服力有效的语言艺术,其巧妙运用常常能达到意想不到的教学效果.  相似文献   

15.
国家大力发展高职教育的今天,为培养合格的高素质人才,如何培养提高学生的道德素养,从分析当前道德教育存在的困惑,面临的挑战,提出高职院校道德教育的探索方向,确定道德教育体系,提高整体道德水平.切实加强高职院校道德教育的紧迫感和使命感.  相似文献   

16.
当前农村的德育教育滞后于社会的发展,影响新农村精神文明建设.实现转变重智轻德的德育观念,解决农村孝道缺失的问题,培养明是非、辨善恶、知荣辱的道德评价能力的德育教育转型具有重要的现实意义.参3.  相似文献   

17.
高职院校德育工作的创新性探讨   总被引:2,自引:0,他引:2  
阐明创新在职校思想政治工作中的地位和作用.寻求新时期职校学生思想政治工作的突破点,创新德育方法,提高思想政治工作的针对性和实效性,做到继承和创新相结合,提高预见性.  相似文献   

18.
道德和利益的关系问题体现了伦理学研究对象的矛盾特殊性,是研究和解决其他一切伦理问题的前提和基础.这个基本问题包含的最重要的一方面就是经济利益和道德的关系问题.因此,研究公司理财的德得之道无疑是研究伦理学基本问题不可或缺的组成部分.参9.  相似文献   

19.
加强个体道德自律不仅是规范网络交往的必需,也是个体自我完善和发展的必需.本文以个体道德自律为立足点,试图就加强个体道德自律的途径这一问题作尝试性的探索.  相似文献   

20.
中华传统文化在大学生品德修养中的作用   总被引:2,自引:0,他引:2  
加强大学生品德修养是高校的根本任务之一。传统文化凝聚了民族精神的精华,是中华民族之魂,它具有永恒的价值。优秀的传统文化有利于大学生爱国精神的培养,有利于大学生自强不息、积极进取精神的培养,有利于大学生道德感和责任感的提高,有利于大学生人格的完善,有利于大学生博大胸襟的形成。  相似文献   

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