Short- and long-term effects of site factors on net N-mineralization and nitrification rates along an urban-rural gradient

Long- and short-term effects of urban site factors on net N-mineralization and nitrification rates were investigated in oak stands along an urban-rural land-use transect in the New York City metropolitan area. We used reciprocal transplants of undisturbed soil cores between urban and rural forests to determine the relative importance of long-term effects (mor vs. mull soils, quality of soil organic matter, and deposition of N) vs. short-term effects (soil temperature) of urban factors in controlling field N-transformation rates along the gradient. In addition, undisturbed soil cores from surface (A, Oe horizons) and subsurface (B horizon) soil were collected from urban, suburban, and rural stands and allowed to incubate in these respective sites to compare the net effect of all urban factors with transplanted-core results. The transplant experiment revealed that soil type (long-term) affected net N-mineralization and nitrification rates. Urban soils nitrified nearly 6.3 and 5.4 times more than rural soils incubating in urban and rural stands, respectively (p = 0.003 and p = 0.002, respectively). Similarly, in rural stands total accumulation of inorganic N was 87% higher in urban than in rural soils, whereas in urban stands, urban soils mineralized 83% more N than rural soils (p = 0.043 and 0.08, respectively). Comparing soils incubating in their native locations, urban soils incubating in urban stands mineralized more than 2.5 times the amount of N than rural soils incubating in the rural stands (p = 0.019). By contrast, urban soils incubating in urban stands exhibited a 8-fold increase in nitrification over rural soils incubating in rural stands (p = 0.008). As with the transplanted cores, the urban and suburban environments had a positive effect on net rates of N-mineralization and nitrification in both surface and subsurface layers of soil. The surface layer of suburban and urban stands had a 3- and 2.3-fold higher accumulation of net inorganic N than rural stands (ANOVA, p = 0.05). Similarly, in the subsurface layer both urban and suburban stands had 2.6-fold higher net N-mineralization rate than rural stands (ANOVA, p = 0.01). Along this urban-rural gradient, soils in oak stands exhibit higher net nitrification and, to a lesser extent, net N-mineralization rates in urban and suburban stands than in rural stands. Results from the transplant experiment and in situ measurements of surface and subsurface soil indicate that long-term effects (mor vs. mull soils, N deposition) contribute to the higher N-transformation rates in urban and suburban stands. As a result of these effects, urban and suburban stands have the potential for higher losses of N than rural stands.     

关于姚鼐章学诚批评《文选》分类之得失问题--兼论"七""设论"与赋的关系

<文选>分类的确有可议之处,尤其是其小类.然这往往是"天然地"存在的,故只要对一大批文章进行较细的分类,就难以完全避免他人之"议".姚鼐、章学诚诸家的批评主要是因其没有充分地考虑到实际操作与理论要求间的差异及其"不思当时事实"所致.姚说似是而非,<古文辞类纂>亦多类似<文选>之"失";章说太半责非其所当责,少半或有理而萧统"持之有故".<文选>在文体分类方面的历史贡献是巨大的,尽管其更多的只是继承而非新的建树.     

对哲学“物质”概念的思考

物质,这个古老的唯物主义哲学概念,经过马克思主义经典作家恩格斯和列宁的"扬弃",曾使辩证唯物主义和历史唯物主义的发展获得了新的生机和活力。列宁的物质概念从提出到现在已近一个世纪。20世纪的科学技术取得了突飞猛进的发展,人类社会也发生了翻天覆地的变化,微电子技术特别是发达的电脑网络技术将我们带入数字化空间。人类已经迈入21世纪,进入信息化社会,跨入知识经济时代,而我们的物质概念依旧停留在20世纪初的水平上。我认为,对物质概念进行新的"扬弃"的时机和条件早已成熟,文章通过对恩格斯与列宁的物质概念的追述、内涵与外延的比较与分析,找出其时代的局限性与逻辑上的缺陷或不足,并在此基础上提出了存在、实在(物质)、虚在、客观存在、非客观存在、现实性空间、非现实性空间和实践诸范畴,试图赋予物质(即实在)以新的意义和时代特色。     

李时珍、宋应星气学思想合论

科学与唯物主义具有本质的一致性。本文从历史与逻辑相统一的角度,论述和分析了我国古代两位杰出科学家李时珍、宋应星的气学思想,并对这一思想在我国科学和哲学发展史上的地位和作用作了评价。     

Integrating risk assessment and life cycle assessment: a case study of insulation.

Increasing residential insulation can decrease energy consumption and provide public health benefits, given changes in emissions from fuel combustion, but also has cost implications and ancillary risks and benefits. Risk assessment or life cycle assessment can be used to calculate the net impacts and determine whether more stringent energy codes or other conservation policies would be warranted, but few analyses have combined the critical elements of both methodologies In this article, we present the first portion of a combined analysis, with the goal of estimating the net public health impacts of increasing residential insulation for new housing from current practice to the latest International Energy Conservation Code (IECC 2000). We model state-by-state residential energy savings and evaluate particulate matter less than 2.5 microm in diameter (PM2.5), NOx, and SO2 emission reductions. We use past dispersion modeling results to estimate reductions in exposure, and we apply concentration-response functions for premature mortality and selected morbidity outcomes using current epidemiological knowledge of effects of PM2.5 (primary and secondary). We find that an insulation policy shift would save 3 x 10(14) British thermal units or BTU (3 x 10(17) J) over a 10-year period, resulting in reduced emissions of 1,000 tons of PM2.5, 30,000 tons of NOx, and 40,000 tons of SO2. These emission reductions yield an estimated 60 fewer fatalities during this period, with the geographic distribution of health benefits differing from the distribution of energy savings because of differences in energy sources, population patterns, and meteorology. We discuss the methodology to be used to integrate life cycle calculations, which can ultimately yield estimates that can be compared with costs to determine the influence of external costs on benefit-cost calculations.     

马克思物质变换理论与中国生态环境问题的成因分析

马克思物质变换理论是马克思在《资本论》中提出的关于人与自然进行物质交换以及实现物质循环的理论观点,是马克思生态思想的重要组成部分。物质变换不仅需要在消费领域、生产领域实现,也同样需要在流通领域实现。物质变换受阻是导致生态环境问题产生的直接原因。当前,不合理的产业结构、外向型经济占主导地位的经济政策以及化石能源的过度依赖是造成物质变换和物质循环受阻,进而产生中国生态环境问题的重要成因。     

李煜词浅论

南唐后主李煜的词,对后世产生了极大的影响,其一是他拓展了词的表现题材,摆脱了花间派专事妇女描写的局限;其二是他善于运用贴切的比喻,使抽象的感情形象化、具体化;三是他的语言风格明净优美、朴素自然,接近口语     

《雨中的小猫》隐喻序列的对抗性－－兼评海明威性格矛盾性

用隐喻的方式及结构来描写、阐释人物和事件,使得表层意义下寓含深层的主题意旨生动地突现出来,这是20世纪现代文学阐述主题的一个重要手段.本文深入研究海明威的短篇小说<雨中的小猫>中的多个隐喻,并对它们所显示出来的序列对抗性进行论证和分析,同时指出该隐喻序列的对抗性折射出海明威性格中的矛盾性.     

人类自由与“美的规律”

人类最高的自由不能在必然性领域里寻到,只能存在于超必然性的世界。思维或精神自由是人类最彻底的自由。马克思提出“物的尺度”、“人的尺度”以及“美的规律”等概念,与真、善、美密切相关,且是一个渐次升高的系列。隐含着真和善的“美的规律”是人类实践活动必须遵循的最高规律,是人类向自由世界迈进的路标。     

湘绣题材的功能形成、分类及文化内涵

湘绣创作离不开题材的选择,为了给湘绣创作者提供更多的选择参考,有必要对湘绣题材的 功能形成进行探讨,对众多已出现的湘绣题材进行分类并分析其文化内涵。理论上,湘绣题材的选择 范围相当广泛,但在湘绣的实际创作中,其题材选择受到诸多因素的影响。其中,文化因素是决定湘 绣题材选择的隐性因素,实际用途是影响湘绣题材选择的显性因素。从其用途上看,湘绣题材可分为 祈福禳灾、赏心悦目、怡情悦性、修身养性四大类型,并且每一类型都具有独特的文化内涵和代表性 作品。