西安城市化进程与环境生态问题研究

通过对西安城市化过程的分析,得出50年来西安城市化的发展大体经历了三个阶段:快速发展阶段,停滞阶段和稳步上升阶段。城市化水平的提高与国民经济的增长基本同步,回归分析表明:西安城市化水平与人均GDP的对数呈正比关系,城市化水平的提高有效地推动了社会经济的发展。在城市化进程中,产业结构的调整与第二、第三产业比重的上升加速了城市化的推进。第三产业在国民经济中的比重与城市化水平呈正相关系。伴随城市化的发展,出现了耕地面积减少及大气污染、水污染、固体废物污染、噪声污染等环境生态问题,通过对城市化过程中的环境生态问题分析,指出实现西安城市化可持续发展的基本途径。     

京张区域生态与环境特征及问题分析

京张区域是中国首都圈的生态功能核心区域,通过分析认为,该区域环境具有区位特殊性、系统脆弱性、功能一体性、地域分割性、发展二元性等特征,存在有干旱缺水、土地沙漠化、水土流失、风沙危害、环境污染等突出问题。北京作为特大城市发展所依赖的周边环境与上海、广州等城市有本质不同,必须作为特殊情况给予高度重视。     

汉唐间敦煌地区的环境生态问题及其治理研究

对汉唐之间敦煌地区由于过度开发所造成的环境生态问题及当地民众为应对生态环境问题加剧所采取的治理举措进行了梳理和研究,以期为今天敦煌地区建设资源节约型、环境友好型社会提供有益的历史借鉴。     

塔里木河下游生态输水前后生态与环境的动态变化研究

早在4000年前的原社社会,塔里木河(以下简称塔河)下游绿色走廊已经形成。在近百年的历史中,前20年是绿色走廊的兴盛时期,自20世纪20年代中期以后,绿色走廊开始近代历史上的衰败过程,特别是近50年来塔里木河上中游的水土开发活动,使得下游地区的来水量骤减并中断有近30年的历史,从而引发了下游绿色走廊的逐步走向衰败、土地荒漠化趋势加剧等生态环境恶化问题。为了改善塔河下游地区的生态与环境、抑制土地退化的加剧、挽救濒临灭绝的下游天然植被,截止2005年11月共向该地区输水7次,断流30年的塔里木河下游完成了第四次应急输水后,大体达到维系下游生态的必须水量,输水使河道两侧植被生长状况发生明显改善,生物呈多样化变化。笔者在1998年5月,2002年10月和2004年5月三次对塔河中、下游地区进行实地考察获得了第一手资料,本文在前人研究的成果基础上和实地考察资料相结合,对塔里木河下游生态输水前后生态与环境的动态变化进行探讨。     

对新疆生态环境问题及其对策的若干思考

新疆分布着我国重要的绿洲农业区 ,又是我国资源能源的接替区。在经济发展取得长足进步的同时 ,新疆的生态环境问题日益突出。清醒、客观、准确地认识新疆的生态环境现状 ,制定相应的环境保护对策 ,对于新疆经济社会的可持续发展是十分重要的。本文从了解新疆的自然环境、社会经济特征入手 ,分析了生态环境变化的趋势和主要的生态环境问题 ,提出了有针对性的生态环境保护对策和建议     

资源环境产权缺陷与矿区生态补偿机制缺失:影响机理分析

矿区生态环境持续恶化的根源在于资源环境产权制度的缺失。我国矿产资源产权制度主要存在所有权、管理权、经营权混淆导致权责不清,采矿权权能残缺,以及一元矿权与二元地权的矛盾与冲突问题。对环境质量的使用权尚没有在法律层面上进行明确界定。对榆林矿区的实证研究表明,在矿产资源开发中利益主体与生态补偿的责任主体严重背离。只有从改革资源环境产权制度着手,才有望建立完善的矿区生态补偿机制,从而彻底解决矿区生态环境问题。     

玛纳斯河流域生态与环境需水研究

在总结国内外关于生态和环境需水研究的基础上,本文界定了玛纳斯河流域生态与环境需水的内涵。结合国内外生态与环境需水量的计算方法和玛纳斯河流域的实际情况,初步探讨了玛纳斯河流域生态和环境需水的研究思路、计算内容和方法,并对玛纳斯河流域的生态与环境需水进行了分析计算,从而为定量评价玛纳斯河流域水资源的合理配置提供理论基础。     

新疆平原绿洲环境变化与生态维护

干旱区陆地生态系统的稳定性主要受控于水分因素,绿洲环境变化既相互联系,又互相制约,但都有自身的生态系统特点和对人类服务的功能。对新疆平原地区绿洲环境的变化进行分析发现,人工绿洲扩大和发展、城镇绿洲兴起和开拓、天然绿洲缩小和维护的总趋势。因此,需要在以流域或盆地为单元,以水为纽带并受水资源条件的限制,对流域或盆地内的所有农业绿洲、城镇绿洲和天然绿洲等生态系统与荒漠生态系统进行总体的水资源消耗平衡与生态平衡规划,科学配置水资源,才能维护相互的依存关系,并使各类绿洲得到生态维护。     

环境规制对煤炭企业生态投资的影响——基于面板数据的实证分析

利用2009-2015年我国煤炭上市公司的数据,建立面板回归模型,定量分析了命令控制型和市场激励型环境规制对煤炭企业生态投资的影响。实证结果表明:我国环境规制强度与煤炭企业的生态投资存在"U"型关系,我国命令控制型环境规制对煤炭企业生态投资的作用处于正向拉动阶段;税收优惠和财政补贴两项市场激励型规制手段对煤炭企业的生态投资具有显著的激励作用,相比而言,税收优惠政策的作用小于财政补贴政策的作用。     

神府煤田采煤塌陷引起的生态问题探讨

通过野外定位观测和室内分析,研究了神府煤田风沙区采煤塌陷1-2年后地表颗粒组成、土壤水分和植被群落的动态变化及引发的生态问题.结果表明:非塌陷区(对照)沙丘,地表颗粒组成以细砂和极细砂为主,占整个组成的63.76％,而采煤塌陷1-2年后,颗粒组成以粗砂和中砂为主,占整个组成的65％以上,呈现粗化现象,潜在可风蚀性程度加强;形成的塌陷裂缝和地表破损,增加了土壤蒸发面,导致土壤水分降低,和对照相比,地表层(O-20cm)范围内的土壤水分流失量最大,达151％,中间层(30-70cm)流失139％,深层(70cm以下)流失101％,整个沙丘典型位置的累积土壤水分流失量达392％,且随着剖面深度的增大而减小,直接加剧了沙质土壤的旱化;采煤塌陷引起的塌陷裂缝、地表破损、地表颗粒粗化以及土壤水分的流失等因素,促使植被大量死亡,植被的死亡率加大又直接反作用于塌陷地表,在风的作用下引发严重风蚀.     

论西部大开发中张掖市生态环境建设问题

张掖市长期受干旱、大风及沙尘暴影响,生态环境极为恶劣,制约着西部大开发建设进程。其存在的重要问题是:水资源匮乏,植被破坏严重,覆盖率低等;针对具体情况提出:改善水资源条件和恢复植被是张掖地区生态环境建设的重点。     

Effects of vegetation patterns and environmental factors on woody regeneration in semi-arid oak-dominated forests of western Iran

This study assesses the effects of vegetation patterns and environmental factors on the abundance of natural tree and shrub regeneration in semi-arid forests of the Zagros Mountains, western Iran. We sampled 120 releves at different topographic positions in a protected area of the studied region. Floristic composition, slope, elevation and soil properties were recorded at each releve, and woody seedling density was measured. We have first discerned five floristic groups using two-way indicator species analysis(TWINSPAN), detrended correspondence analysis(DCA), and canonical correspondence analysis(CCA) and then explored the relationships among the floristic group compositions, environmental factors and seedling densities. The indicator species of the five groups were Quercus brantii, Acer monspessulanum, Cerasus microcarpa, Rhamnus arvensis and Astragalus licyoides. Our results indicated that these groups were significantly affected by elevation and soil properties and the soil properties refer to: EC(electrical conductivity), N(nitrogen), K(potassium), OM(organic matter), and bulk density. Woody regeneration was composed of Q. brantii, A. monspessulanum, C. microcarpa, Amygdalus scoparia and Crataegus pontica seedlings. The highest density of seedlings was found for Q. brantii(97.14(±48.00) plants/hm~2) and the lowest for A. scoparia(2.28(±1.50) plants/hm~2). Quercus brantii was the dominant species and the seedling density was positively correlated with soil p H and P(phosphorus) values. Amygdalus scoparia regeneration was negatively correlated with elevation, and the seedling density peaked in C. microcarpa group. There was no significant variation in distribution of C. pontica seedlings among the groups, but the seedling density of this species was positively correlated with slope and K. Cerasus microcarpa seedlings were more abundant in the Q. brantii group than in other groups. This study showed that the regeneration of tree and shrub species was unequally distributed in different floristic groups for some species(A. scoparia and C. microcarpa) but not for other(Q. brantii and C. pontica) and was generally correlated with some environmental factors, particularly elevation, slope and soil nutrients(P and K). These results are a first step to implement future management and restoration strategies for promoting forest regeneration.     

Trichoderma: systematics, the sexual state, and ecology

ABSTRACT A chronology is presented that charts the development of a genus and species concept in Trichoderma. Eighty-nine species of Trichoderma have been named, and several species of Hypocrea have been linked to unnamed Trichoderma anamorphs. Eighty-three taxa of Trichoderma and their teleomorphs, Hypocrea spp., have been included in phylogenetic analyses, including 11 species of Hypocrea with unnamed Trichoderma anamorphs. Phylogenetic analyses show that Trichoderma and Hypocrea are congeneric. Trichoderma species not linked to Hypocrea teleomorphs are derived from among species that are linked to teleomorphs, indicating sexual and asexual lineages are not independent of each other. Many more species remain to be discovered and described. Molecular phylogenetic analyses have revealed the existence of more species than have been recognized on the basis of morphology alone. A suggestion is made to modify the International Code of Botanical Nomenclature to enable adoption of a single generic name for Trichoderma/Hypocrea, with Trichoderma being the older and more utilitarian name. As increasing numbers of species are studied, the few morphological characters of anamorph and teleomorph have reached their limit for defining species. DNA-based characters have assumed an indispensable role. Exploration of new niches, such as within tree trunks and new geographic locations, have resulted in a substantial increase in the number of species of Trichoderma. Trichoderma is usually considered a genus of free-living soil fungi but evidence suggests that Trichoderma species may be opportunistic, avirulent plant symbionts as well as parasites of other fungi. Members of the genus Trichoderma are universally present in soils, although individual species may be either cosmopolitan (e.g., T. harzianum) or limited (e.g., T. viride) in their geographic distribution. To facilitate identification of species, a list of correctly identified strains of Trichoderma and their GenBank numbers for sequences of translation-elongation factor EF-1alpha and internal transcribed spacer rDNA is provided.     

Weed dynamics in the Mediterranean urban ecosystem: ecology, biodiversity and management

This paper presents a review of weed dynamics in the Mediterranean urban ecosystem, seen both in an ecological and biological perspective and also in relation to the interaction between human activity and the survival strategies of the various phytocoenoses. Although generalizations on urban weeds cannot easily be drawn on account of the wide range of microenvironments, anemochoric dissemination mechanisms (Asteraceae), resilience (grasses) and perennation are of particular importance. The reasons underlying the undesirability of weeds in the urban environment are investigated. Not only are weeds considered unsightly, but they may also give rise to ‘functional’ obstacles, damaging sidewalks or clogging storm drains. Furthermore, they may adversely affect human health by releasing allergenic pollen into the atmosphere. Management of urban weeds is based almost exclusively on mechanical control, as chemical measures may involve a toxicity risk for man. Paradoxically, certain weeds species may however have a positive effect if they are linked to fauna (butterflies, birds, etc.) considered to give a favourable impression in the cityscape. Finally, the possibility of favouring the biodiversity of the urban ecosystem by introducing some wildflowers typically associated with the degree of biodiversity of the surrounding environment is discussed.     

Germination ecology of Leptochloa chinensis: a new weed in the Italian rice agro-environment

Leptochloa chinensis is a new weed that has been found with increasing frequency in Italian rice paddies. The germination ecology of L. chinensis seeds was studied in order to investigate the development mechanisms and survival strategy of this weed in rice paddies of northern Italy. Leptochloa chinensis seeds showed no dormancy and exhibited germination even in anoxic conditions. Germination was strongly influenced by temperature (minimum around 15°C; optimal 25–35°C) and light (phytochrome dependent). Temperature fluctuation caused an increase of seed germination in the dark. Seed burial also strongly inhibited germination and emergence of this species. At 5 cm seed burial only 5% of seedlings emerged in flooded conditions, while at the same depth, but with no flooding, no seedling emergence was observed. This phenomenon was not due to oxygen depletion, as germination was not inhibited by complete anoxia, as demonstrated by the fact that some seedlings did emerge in flooding conditions when water was no deeper than 6 cm. Seed burial and concomitant flooding induced an unusual germination: first coleoptile emergence and subsequently emergence of the radicle was observed. The possible exploitation of this knowledge for weed management is discussed.     

The role of ecology in the development of weed management systems: an outlook

This paper discusses the extent to which a knowledge of weed biology and ecology can contribute to the development of weed management strategies. To date, such contributions have been modest and have been constrained by a number of factors that are discussed in this review. In contrast to other pest management disciplines, devising integrated weed management strategies that address a diversity of weed species with a diversity of life history traits is difficult. Because of this diversity, robust systems that require ecological insight beyond that of individual species are needed. Although the contributions have been modest, research findings have helped to shape weed management strategies in a number of important ways. Approaches directed at weed population management have revealed important insights into population equilibria, density-dependent mortality and life stages particularly important in regulating population size. Eco-physiological research has helped to guide the development of biologically effective herbicide dosage strategies, whereas mechanistic interplant competition modelling coupled with empirical field studies have aided in the identification of weed-suppressive crop phenotypes. Finally, much has been learned about the influence of control tactics and agronomic measures on the evolution of herbicide resistance and the development of integrated weed management strategies to address it. In this paper, examples are reviewed where research in ecology and biology has helped to shape the practice of integrated weed management. More importantly, characteristics of such research programmes are identified so that future efforts in the discipline will have a context in which the relevance of research questions and approaches can be considered.     

呼和浩特市环境库兹涅茨曲线与环境影响因素分析

为探究呼和浩特市经济发展与城市环境污染之间的关系,文中对工业三废排放量与人均GDP进行库兹涅茨曲线拟合;并选取四组环境影响因子,比较四组因子与环境污染物排放的灰色关联度.结果表明,工业污水拟合结果不佳,;工业废气与工业固废排放量与经济增长同向变动;环保科技进步与政府环保措施这两部分因子对环境的影响较大.可知,呼和浩特市可通过优化产业结构、促进生产与环保技术进步、增加政府环境投资实现经济环境的协调发展.     

Weed management in organic agriculture: are we addressing the right issues?

Summary Despite the serious threat which weeds offer to organic crop production, relatively little attention has so far been paid to research on weed management in organic agriculture, an issue that is often approached from a reductionist perspective. This paper aims to outline why and how this problem should instead be tackled from a system perspective. Compared with conventional agriculture, in organic agriculture the effects of cultural practices (e.g. fertilization and direct weed control) on crop:weed interactions usually manifest themselves more slowly. It follows that weed management should be tackled in an extended time domain and needs deep integration with the other cultural practices, aiming to optimize the whole cropping system rather than weed control per se . In this respect, cover crop management is an important issue because of its implications for soil, nutrient, pest and weed management. It is stressed that direct (physical) weed control can only be successful where preventive and cultural weed management is applied to reduce weed emergence (e.g. through appropriate choice of crop sequence, tillage, smother/cover crops) and improve crop competitive ability (e.g. through appropriate choice of crop genotype, sowing/planting pattern and fertilization strategy). Two examples of system-oriented weed management systems designed for organic agriculture are illustrated as well as future perspectives and problems.     

A review of the ecology and control of thistles in Australia

Studies on the ecology and control of thistles in Australia, particularly those related to pasture improvement, are reviewed, and the results used to interpret increases and changes in thistle dominance. Several hypotheses, based on ecological differences in the thistles, their life cycles and changes in the soil/seed environment may explain the changing species incidence in the field, and it is postulated that, within a restricted group of competing thistle species, it may be more meaningful to interpret these ecological differences in terms of ‘tolerance of unfavourable conditions’ than in terms of ‘optimal requirements’. Alternative strategies for the control of thistles, including pasture competition, grazing management, the utilization of high soil fertility, and chemicals, are also assessed. It is re-emphasized that the aim of any long-term programme to control thistles, with or without the release of biological agents, should be the establishment and/or maintenance of a vigorous perennial pasture. The relative importance of different thistle species in Australian pastures and the ecology and dynamics of soil seed banks are identified as important areas for future thistle research.     

Fifty years of the integrated control concept: the role of landscape ecology in IPM in San Joaquin valley cotton

In defining the integrated control concept, Stern, Smith, van den Bosch and Hagan described ‘understanding the ecosystem’ as a key underpinning of the concept. In following years, Stern and van den Bosch continued to refine and expand the role of the ecological landscape. They and their colleagues developed cultural practices that took advantage of this understanding to limit the need of pesticide intervention in cotton in the San Joaquin Valley during the 1960s and 1970s. Research and extension activities in the intervening years built upon those fundamental concepts using geospatial tools and analytical techniques to refine current understanding and develop ecological landscape level approaches to manage Lygus hesperus (Knight) in San Joaquin Valley cotton, Gossypium hirsutum (L.) and more recently G. barbadense (L.). The result has been a significant drop in insecticide use against L. hesperus, with less than one application per season during the 1990s and early 2000s. Copyright © 2009 Society of Chemical Industry