感应电动势与参照系的相对关系

本文从电磁场变换入手,举例说明感应电动势的大小及区分感生、动生电动势与参照系有关.     

Foraging responses of wild house mice to accumulations of conspecific odor as a predation risk

Many predators hunt using the social and waste odors of their prey. It is unknown, however, whether potential prey modify their behavior in response to the risks of predation associated with accumulations of conspecific odor. We examined this question by measuring foraging trade-offs of wild house mice (Mus domesticus) in the field where we increased both predation risk and conspecific odor at artificial food patches in a two-factor design. Mouse giving-up densities (GUDs) were significantly higher in open habitats than in closed habitats but did not differ with the addition of mouse odors. Fine-scale behavioral observations of captive mice confirmed their attraction to the conspecific odor in an enclosure experiment, without any change to the GUD. These results indicate that house mice continue to visit and forage at food patches despite accumulations of predator-attracting odors. This most likely occurs for the social benefits obtained from conspecific odor exploration; however, such behavior may cause mice to become vulnerable to considerable olfactory exploitation by their predators. Future work must therefore focus on how mice trade off the social benefits of investigating odors that also attract their enemies.     

松嫩平原西部不同土地覆被水盐动态对比研究

通过对6种土地覆被2003年6～10月水盐时空动态进行分析，对比不同土地覆被水盐动态变化差异，结果发现：采样期内，不同土地覆被(碱斑地除外)0-120cm剖面含水量均出现明显峰值，大豆地和羊草草地在7月底出现峰值，玉米地和向日葵地在8月初，退化草地则在8月底才达到，比羊草草地滞后了一个月。除羊草草地外，其他土地覆被剖面含水量变化呈W型，只是波动幅度各不相同。采样期内，羊草草地剖面含水量的相对变率最大，为74％，其他依次为退化草地、大豆地、向日葵地、玉米地，碱斑地最低，仅为6．4％。相对于农田土地覆被，在0～40cm，羊草草地、退化草地和碱斑地随盐渍化程度的加重，含盐量剖面变异逐渐减小，而农田的三种土地覆被之间变异比较接近。整个采样期，向日葵地储盐量随时间的变化呈下降趋势，其他土地覆被波动变化一致，都经历了下降-上升-下降过程，但波动幅度不同，且羊草草地在7月7日出现上升，其他4种土地覆被在9月8日开始出现滞后于含水量的变化。相对于采样初期，不同土地覆被含盐量的相对变率均为负值，农田的下降幅度大，草地次之，碱斑地最小。协方差分析表明：95％置信度下，土地覆被、土壤剖面和两者的交互作用对含盐量的影响差异显著。     

水生态修复对莲花湖底栖动物群落的影响

武汉莲花湖是典型的富营养化城市浅水湖泊．通过对其进行16mo的监测后发现，治理后的小莲花湖比大莲花湖水质有明显改善．监测期间小莲花湖底栖动物密度和生物量均值明显高于大莲花湖，Shannon多样性指数与Margalef多样性指数也高于大莲花湖．将大、小莲花湖的10种环境因子和底栖动物密度进行典型相关分析后，发现总磷、温度、总氮、叶绿素a、氨离子是对底栖动物群落具有显著性影响的环境因子．图8表3参20.     

关于肥满度指数的讨论

肥满度指数,也称身体状况指数,广泛应用于各个动物类群和生态学、生理、生化、遗传学以及养殖业.至今已有多种肥满度指数提出,从计算公式结构上,肥满度指数可以划分为比值法和残差法两大类.通过对各种肥满度指数的分析,Le Cren相对状态指数Kn、log10(体重)与log10(身体大小指数)线性回归的(标准化)残差这两种肥满度指数系统误差相对较小.实际应用中最好根据所考察的问题分别计算不同年龄段、性别的个体的肥满度指数来分析肥满度指数.由于定义的模糊性及其前提假设缺乏广泛验证,因此,肥满度指数在实际应用中需要谨慎考察其前提假设是否满足.参33     

Density and extra-pair fertilizations in birds: a comparative analysis

Møller and Birkhead (1992, 1993) reported that extra-pair copulations (EPCs) occur more frequently in colonial than dispersed nesting birds. We comprehensively reviewed published data to investigate how breeding density affects extra-pair fertilizations (EPFs). Within species EPFs appeared to increase with density: two of three studies on colonial breeders and six of eight on dispersed nesters showed increases in EPFs with increasing density. However, comparisons among species (n?=?72) revealed no evidence that EPF frequencies correlated with (1) nesting dispersion, (2) local breeding density, or (3) breeding synchrony, even when each of these variables in turn was held constant and phylogenetic relationships were taken into account via contrast analyses. Methodological and biological reasons for the disparity between observational studies of EPCs and molecular genetic analyses of EPFs are discussed.     

沈阳市区大气颗粒物元素组分及其分布

本研究采用美国安德逊五段冲击式采样器进行大气颗粒物采样，用中子活化法进行分析，获得４３种元素质量浓度，并求得各种元素的质量中值直径和几何标准差。     

Roads and Landscape Pattern in Northern Wisconsin Based on a Comparison of Four Road Data Sources

Abstract:  Roads are important components of landscapes; they fragment habitat, facilitate invasive species spread, alter hydrology, and influence patterns of land use. Previous research on the ecological impacts of roads may have underestimated their effect because currently available sources of road data do not include the full road network. We compared differences in road density and landscape pattern among U.S. Census Bureau TIGER line files, U.S. Geological Survey 1:100,000-scale digital line graphs, and U.S. Geological Survey 1:24,000-scale digital raster graphics in northern Wisconsin to road data derived from 1:40,000-scale digital orthophotos. Road density measured from digital orthophotos (2.82 km/km²) was significantly greater than that of digital raster graphics (1.62 km/km²) and more than double that of digital line graphs (1.21 km/km²) and TIGER (1.27 km/km²) data. The increased road densities in raster graphics and orthophoto data were mainly due to the addition of minor roads. When all roads were used to define patch boundaries, landscape metrics produced with orthophoto data showed significantly greater levels of fragmentation than those based on line or raster graphics. For example, maximum patch size was 1074 ha and total edge was 109 km for line graphs, compared with 686 ha and 211 km for orthophoto data. Roads are missing in commonly used data, primarily because mapping standards systematically exclude minor roads. These standards are not ecologically based and may result in false assumptions about the ecological effects of roads. We recommend that future studies take special consideration of the completeness of road data and consider whether all ecologically relevant roads are included.     

封育次生马尾松(Pinus massoniana)林优势种群竞争密度效应

以退化红壤区封山育林植被恢复过程中优势种群马尾松为研究对象,研究不同恢复阶段马尾松种群竞争密度效应,并提出一个适用性更强的竞争密度效应模型.研究表明,退化红壤区植被恢复过程中优势种群马尾松竞争密度效应明显,优势种群平均胸径(D)、平均胸高断面积(S)、平均单株材积(V)、林分蓄积量 (M)与种群密度 (ρ)的竞争密度关系密切,达到极显著水平(α<0. 01);新竞争密度效应模型较前人模型描述C-D效应效果更理想,可在森林竞争密度效应研究中应用. 表 4参 19     

九寨沟主要植物群落生物量的空间分布

研究了九寨沟自然保护区主要植物群落的生物量以及生物量在九寨沟的空间分布格局 ,并用群落的总生物量量度不同群落在九寨沟陆生生态系统中的相对重要性 .在野外实地调查中 ,采取皆伐法测定了乔木群落林下层以及灌丛和草甸群落的地上部分生物量 ;对样方中乔木的胸径、树高进行了测量 ,利用经验公式估算乔木层的生物量 .研究结果表明 ,所有群落中生物量最大的为亚高山暗针叶林 ,平均为 380thm-2 左右 ,总生物量亦占了整个九寨沟生物量总量的 90 %以上 ,为九寨沟陆地生态系统中最重要的植物群落 ;高山草甸和流石滩植被生物量最小 ,平均为 1thm-2以下 .整个九寨沟的总生物量约为 8.3× 10 6t,平均生产力大于 5 .89thm-2 a-1.垂直分布上 ,生物量一般随海拔的升高而增加 ,在halt=30 0 0m以上达到最大值 ,之后则随海拔的升高而急剧下降 ,这种分布格局与土壤、气候、人类干扰等各种环境因素密切相关 .与全国平均水平相比 ,九寨沟几乎所有类型的群落的平均生物量都要高于全国同类群落的平均水平 .图 3表 4参 18