三种类型森林林下植物多样性及生物量比较

对相同立地条件下海南天然次生林、桉树和马占相思林的林下植物多样性及生物量进行调查,通过比较,灌木植物的物种丰富度S、多样性Simpson指数、Shannon-wiener指数,Margalef指数、均匀度Pielou指数为:天然次生林＞桉树人工林＞马占相思人工林,方差分析前两者之间差异不显著,后两者之间差异极显著;而草本植物的变化趋势为:桉树人工林＞天然次生林＞马占相思人工林,方差分析结果前二者间除均匀度Pielou指数差异不显著外,其它多样性指数间差异极显著,后二者间差异不显著.灌木植物地上部分总生物量的变化趋势为:天然次生林＞桉树人工林＞马占相思人工林,草本植物的变化趋势为:桉树人工林＞马占相思人工林＞天然次生林.     

What makes affirmative action‐based hiring decisions seem (un)fair? A test of an ideological explanation for fairness judgments

Studies show that Whites tend to show the lowest level of support for affirmative action (AA) policies. Opponents of AA often argue that this is because it violates principles of meritocracy. However, self‐interest (based on social identification with those adversely affected) could also explain their opposition. In three studies, we varied whether an Asian or White male is adversely affected by AA to test another explanation; namely, that Whites' fairness judgments are based on both the adversely affected person's race and the fairness evaluator's ideological beliefs. Although we found some support for the meritocratic explanation, this was not sufficient to explain why Whites view AA as (un)fair. Instead, we found strong support for our prediction that Whites who are opposed to equality perceive more unfairness when a White (vs. Asian) was harmed by AA, whereas Whites who endorse egalitarian ideologies perceive the opposite. This finding suggests that neither self‐interest nor meritocratic explanations can fully account for Whites' opposition to AA. Copyright © 2014 John Wiley & Sons, Ltd.     

污泥土地利用对草坪草及土壤的影响

以沈阳北部污水处理厂污泥为研究对象,开展了污泥土地利用对草坪草及土壤环境影响的研究.结果表明,污泥土地利用可提高土壤养分含量特别是土壤中有机质含量;使草坪草获得了良好的生长响应,草坪草生物量增加,绿期延长;使土壤重金属含量有所增加,Cd元素含量超过土壤环境质量二级标准,而土壤Pb、Cu、Zn元素含量均未超过土壤环境质量二级标准;早熟禾对Pb具有良好的吸收富集能力,污泥在25、30、60t·hm^-2低施入量时,结缕草对Cd、Cu、Zn具有良好的吸收富集能力.     

北京大气PM2.5中微量元素的浓度变化特征与来源

为了解北京大气细粒子中微量元素的污染水平和来源,在车公庄和清华园进行了连续1年、每周1次的PM_2.5采样和全样品分析.微量元素浓度的周变化大,尤以冬季为甚,相邻2周最大相差达1.6倍;但除冬季的平均浓度较高之外,其季节变化并不显著.微量元素的富集因子在春季最低,反映了频繁发生的沙尘天气的影响.Se、Br和Pb的浓度比来自于北京A层土壤中的含量要高出约1000～8000倍,表明它们主要来自于人为污染.其中Se的富集度最高,反映了北京细粒子来自于燃煤污染的特征.Pb的年均浓度(0.31μg·m^-3)虽然未超过WHO的年均标准,但与洛杉矶和布里斯班相比处于较高的水平;与Br、Se的比较分析表明,燃煤可能是Pb除机动车排放之外的另一个重要来源.     

Cadmium-induced DNA damage and mutations in Arabidopsis plantlet shoots identified by DNA fingerprinting

Random amplified polymorphic DNA (RAPD) test is a feasible method to evaluate the toxicity of environmental pollutants on vegetal organisms. Herein, Arabidopsis thaliana (Arabidopsis) plantlets following Cadmium (Cd) treatment for 26 d were screened for DNA genetic alterations by DNA fingerprinting. Four primers amplified 20-23 mutated RAPD fragments in 0.125-3.0 mg L⁻¹ Cd-treated Arabidopsis plantlets, respectively. Cloning and sequencing analysis of eight randomly selected mutated fragments revealed 99-100% homology with the genes of VARICOSE-Related, SLEEPY1 F-box, 40S ribosomal protein S3, phosphoglucomutase, and noncoding regions in Arabidopsis genome correspondingly. The results show the ability of RAPD analysis to detect significant genetic alterations in Cd-exposed seedlings. Although the exact functional importance of the other mutated bands is unknown, the presence of mutated loci in Cd-treated seedlings, prior to the onset of significant physiological effects, suggests that these altered loci are the early events in Cd-treated Arabidopsis seedlings and would greatly improve environmental risk assessment.     

Can Labor Out-Migration Reduce Firewood Consumption by Rural Households in Western Mountainous China

The relationship between out-migration of labor in the Qinling mountain area and households’ firewood consumption is explored. Migration and remittances reduce households’ firewood consumption due to increases in both income and opportunity cost of firewood collection. Previous studies have been equivocal because they ignored uncertainty in household economy, which is widespread in forest areas of less developed countries. This study provides additional insight by considering vulnerability and subjective assessment of poverty generated by unstable income and an uncertain future. We provide evidence that the amount of firewood consumed depends on income and opportunity cost of firewood collection, but also on a prudent consumption strategy, due to farmers’ subjective assessment of their future possible poverty. We also find out-migration of labor can reduce per capita firewood consumption but subjective poverty also acts against reduction of firewood consumption.     

Optimal heat rejection pressure for transcritical CO2 refrigeration cycle with an expander

Heat rejection pressure plays an important role in designing a transcritical CO₂ refrigeration system, and it has an optimal value to maximize the system’s coefficient of performance (COP). With a thermodynamic simulation model, the optimal heat rejection pressure is studied in the paper for an expander cycle, as well as conventional throttle valve cycle. The effects of compressor efficiency, expander efficiency, gas cooler outlet temperature, and evaporation temperature on the optimal heat rejection pressure are analyzed. It is the first time for a transcritical CO₂ expander cycle that the optimal heat rejection pressure is correlated with the gas cooler outlet temperature and the evaporation temperature at given compressor efficiency and expander efficiency. The average deviation from the correlation to simulation results is less than 1.0%. The correlation provides a guideline to system development and performance optimization of a transcritical CO₂ expander cycle.     

重庆主城区建设用地扩展的时空特征及驱动因子分析

以多时相的遥感影像为基础,选用归一化裸露指数（NDBI）、重归一植被指数（RDVI）和改进的归一化水体指数（修改后的NDWI）,通过阈值分割、掩膜处理提取建设用地信息,结合重庆主城区的社会经济数据,利用扩展速度指数、扩展强度指数、扩展弹性指数、紧凑度指数、建设用地扩展系数及扩展方向分析研究了不同阶段建设用地扩展的时空动态特征,并运用灰色关联分析,对建设用地扩展的驱动因子进行探讨。结果表明：1988～2011年重庆主城区建设用地扩展了39332 km2,扩展速度和扩展强度呈现增大的趋势;扩展弹性系数、建设用地扩展系数波动变化,反映了重庆主城区建设用地逐渐由粗放型向集约型转变;建设用地扩展的空间分析表明重庆主城区的城市形态由非紧凑型向紧凑型发展,同时扩展方向具有明显的分异性,主要向正北和西北方向扩展;人口增长,尤其是城市人口的增长是重庆主城区建设用地扩展最主要的驱动因子;经济发展、产业结构变化与建设用地的扩展也有明显的相关性     

Residents’ concerns and attitudes toward a municipal solid waste landfill: integrating a questionnaire survey and GIS techniques

The ever-growing industry of municipal solid waste (MSW) disposal appeals to the growing need for disposal facilities, and MSW treatment facilities are increasingly an environmental and public health concern. Residents living near MSW management facilities are confronted with various risk perceptions, especially odour. In this study, in an effort to assist responsible decision-makers in better planning and managing such a project, a structured questionnaire was designed and distributed to assess the nearby residents’ concerns and attitudes surrounding the Laogang Landfill in Shanghai. Geographic information system techniques and relevance analysis were employed to conduct the spatial analysis of physical perceptions, especially odour annoyance. The findings of the research indicate that a significant percentage of the responding sample was aware of the negative impacts of landfills on the environment and public health, and residents in close proximity preferred to live farther from the landfill. The results from the spatial analysis demonstrated a definite degree of correlation between odour annoyance and distance to the facility and proved that the benefits of the socially disadvantaged have been neglected. The research findings also direct attention to the important role of public participation, information disclosure, transparency in management, and mutual communication to avoid conflicts and build social trust.