新疆塔里木河下游植物群落逆向演替分析   总被引：29，自引：10，他引：29  

刘加珍  陈亚宁 《干旱区地理》2002,25(3):231-236

通过对塔里木河中下游沿河植物群落的调查分析及地下水位下降对地表植被生态过程影响的研究，探讨塔里木河下游近几十年来植被的逆向演替过程，并划分出不同的演替阶段。根据草、灌、乔植被对地下水位具有不同的适应能力，塔里木河下游植物群落退化顺序也不相同，首先是草本退化，其次是灌木退化，再者是乔木退化。经调查分析表明，塔里木河下游植物群落的逆向演替顺序为：矫灌草群落阶段→乔灌群落阶段→乔木或灌木少阶段，在逆向演替过程中，各阶段有规律地进行，群落结构特征、种类组成也都发生了明显的变化。  相似文献   

Religion and technology: refiguring place, space, identity and community   总被引：1，自引：0，他引：1  

Lily Kong 《Area》2002,33(4):404-413

This paper reviews the literature on the religion–technology nexus, drawing up a research agenda and offering preliminary empirical insights. First, I stress the need to explore the new politics of space as a consequence of technological development, emphasizing questions about the role of religion in effecting a form of religious (neo)imperialism, and uneven access to techno-religious spaces. Second, I highlight the need to examine the politics of identity and community, since cyberspace is not an isotropic surface. Third, I underscore the need to engage with questions about the poetics of religious community as social relations become mediated by technology. Finally, I focus on questions about the poetics of place, particularly the technological mediation of rituals.  相似文献   

Promoting social justice and conserving montane forest environments: a case study of Nepal's community forestry programme   总被引：1，自引：0，他引：1  

Netra Prasad Timsina 《The Geographical journal》2003,169(3):236-242

This paper analyses participatory forest policy and the ways it has influenced the relationships between people as it relates to the forest resource management. This case study was conducted in the middle hills of Nepal, and information was collected through direct observation, individual interviews, group discussion and secondary information analysis. It substantiates a few examples of how the community forestry programme can be used as a means to promote the participation of the women, the poor and dalit (untouchables) in forest resource management, as well as enhancing social justice and improving the forest resources in their locality. However, it also demonstrates that though the community forestry programme has a positive impact, it faces several constraints and challenges. The local Forest User Group is controlled by a few élites making the poor and disadvantaged vulnerable to further marginalization. The results of the case study strongly indicate that community forestry processes must address the political, economic and social needs of the forest users, and also provide a neutral platform on which the poor can present their cases.  相似文献   

岷江上游毛榛、辽东栎灌丛及3种人工幼林土壤种子库的比较   总被引：7，自引：0，他引：7  

刘文胜  曹敏  唐勇 《山地学报》2003,21(2):162-168

本文采用野外调查与萌发实验相结合的方法对岷江上游地区自然恢复的灌丛以及 3种人工林的土壤种子库状况进行了比较研究。结果显示 ,各样地土壤种子库的储量为 192 5 0～ 3 13 60粒 /(m2 × 10cm)之间 ,人工林的土壤种子库储量和物种数量都大于自然恢复的灌丛 ,其顺序为连香树Cercidiphyllum japonicum、油松Pinustabulaeformis混交林 >连香树林 >油松林 >毛榛Corylusmandshurica、辽东栎Quercusliaotungensis灌丛 ,各样地土壤种子库密度的垂直分布均为上层 >中层 >下层。在各样地土壤种子库的生活型组成中 ,乔木种类所占比例极少 ,而草本种类的数量较多。在灌丛的土壤种子库中 ,灌木的物种数量及其在种子库中所占的比例均大于人工林。大序醉鱼草Buddlejamacrostachya、喜阴悬钩子Rubusmesogaeus、华西绣线菊Spiraealaeta在种子库中的大量存在明显提高了灌木在各样地土壤种子库中所占的比例  相似文献   

胶茶人工群落在改善山地土壤生态环境上的作用     

汪汇海  李德厚 《山地学报》2003,21(3):318-323

经过多年的实践和研究结果表明，橡胶(Hevea brasiliensis)—茶树(Camellia sinensis)两层人工群落结构，比单一橡胶种植模式有着明显的改善山地土壤生态环境的特点。胶—茶人工群落对减少水土流失，改善土壤微生物状况，增强土壤地表呼吸强度，促进团聚体形成和提高土壤肥力以及增加单产等方面，均有显著的效果。因此，胶—茶人工群落为合理利用我国西部热带山地资源，开辟了一条新的经营种植模式。  相似文献   

盐碱化湿地稻-鱼复合生态系统微生物特征   总被引：1，自引：0，他引：1  

杨富亿  李秀军  王志春  赵春生  朱世成 《湿地科学》2003,1(2):105-110

为揭示盐碱化湿地稻-鱼复合生态系统微生物群落结构特征,1994-1995年,对松嫩平原苏打盐碱化湿地稻-鱼复合生态系统水体与土壤中的微生物数量及种群组成进行了初步研究。结果表明,稻-鱼湿地水体中异养细菌数量显著高于稻田湿地(P<0.05),季节变化特点为秋季>夏季>春季。异养细菌的数量分布与鱼产量有显著相关关系(r=0.879)。稻-鱼湿地系统的土壤微生物数量明显高于稻田湿地(P<0.01)。稻-鱼湿地和稻田湿地分别检测出10个和11个属的异养细菌。稻-鱼湿地系统1个生长期细菌的平均生物量为0.973g/m3,生产量为307.5 kg/hm2,所提供的鱼产力为7.0 kg/hm2。  相似文献   

Representation of fish communities by scale sub-fossils in shallow lakes: implications for inferring percid–cyprinid shifts     

T.A. Davidson  C.D. Sayer  M.R. Perrow  M.L. Tomlinson 《Journal of Paleolimnology》2003,30(4):441-449

The palaeoecological potential of fish scales was assessed by comparing contemporary population data with scale remains obtained from littoral (n = 10) and open water (n = 10) surface sediment samples in two English shallow lakes, Selbrigg Pond and Cockshoot Broad. Scales and/or scale fragments were present, in low numbers (<20 per 100 cm³ wet sediment) in 34 of 40 sediment samples. In accordance with fish population data, higher densities of scale remains were found in Selbrigg compared to Cockshoot, and in littoral compared to open water samples. Taxonomic difficulties, exacerbated by scale fragmentation, made it impossible to assign the majority of remains to individual species. Most remains could, however, be placed into one of two groups: (i) percids – represented by both scales and scale fragments; and (ii) cyprinids – largely represented by scale fragments. To allow comparison of fish population and sedimentary scale data, both were converted to percentages of the aggregate percid–cyprinid total. Whole scales recovered were almost exclusively percid (45 of 48), thus bore little resemblance to the contemporary fish data. Nevertheless, percentages of scale fragments (Selbrigg: 34 and 66%; Cockshoot: 13 and 87% percid and cyprinid, respectively) and of whole scales and fragments combined (Selbrigg: 54 and 46%; Cockshoot: 46 and 54% percid and cyprinid, respectively) reflected the presence of the numerically dominant fish groups and the broad inter-site differences in their relative abundance (Selbrigg: 36 and 64%; Cockshoot: 10 and 90% percid and cyprinid, respectively). A running mean of scales per sediment volume indicated that some 400 cm³ of sediment was required to accurately characterise the remains present. This study suggests that, with the appropriate methodological considerations (e.g., collection of large sediment samples), fish scale remains may be used to determine the past presence–absence and relative abundance of percid and cyprinid species. As such, this technique may be a valuable supplementary tool for establishing longer-term changes in the fish communities of shallow lakes.  相似文献   

Re-placing the Pilbara's mining unions     

Bradon Ellem 《The Australian geographer》2003,34(3):281-296

This paper examines the attempt by mining management in Western Australia's Pilbara to replace mining unions—quite literally—by removing them from the processes of representation and bargaining. It analyses the way in which those unions have tried to re-place themselves, in the senses of transforming themselves in those spaces in which they were already operating and reviving themselves where they were not. Where unionists have succeeded in these engagements, it has been by working at a range of geographical scales, using the ‘power of place’ in the Pilbara and reshaping traditional geographies of union organisation. It is suggested here that many of these emergent outcomes are the result of the embeddedness of geographically specific historical structures along with new intersections of nationally and locally scaled labour politics.  相似文献   

Quantifying Storm Tide Risk in Cairns   总被引：6，自引：5，他引：6  

Ken Granger 《Natural Hazards》2003,30(2):165-185

The United Nations International Decade for Natural Disaster Reduction (IDNDR)gave rise to an increasing level of attention to the risks posed by a range of naturalhazards and the development of strategies by which to reduce those risks. It waswidely recognised that in order to evaluate risk treatment strategies it was necessaryto `measure' the level of risk that already existed and the level of risk that would beencountered with the treatment strategy(s) in place.This paper outlines the methodology developed under the AGSO (now GeoscienceAustralia) Cities Project to quantify the risk associated with storm tide inundation. It includes the methodology for `measuring' the level of community exposure to storm tide hazards and the methodology for `measuring' community vulnerability. The Far North Queensland city of Cairns is used as the case study to demonstrate the application of these methods.  相似文献   

Community Vulnerability to Tropical Cyclones: Cairns, 1996–2000     

Linda J. Anderson-Berry 《Natural Hazards》2003,30(2):209-232

This paper is a partial discussion of a four-year study that investigated the vulnerability of the people living in the Cairns region to the tropical cyclone hazard. The longitudinal case study, focussing on the Cairns Northern Beaches area, was unique in that it included a social and societal `pre-cyclone impact' evaluation of various resident communities within the region, and then two consecutive `post-cyclone impact' studies. The primary research method supported an inductive qualitative approach to the collection and analysis of survey data. Some quantitative methods were invoked to support qualitative research findings. Survey data was collected in five separate questionnaire-based social surveys that were administered between 1996 and 2000. During the study, residents experiencedthe direct impact of two land-falling tropical cyclones. In addition to this, targeted andfocussed tropical cyclone awareness education was made increasingly available withinthe community. The social and demographic attributes that influence the individual'sperception of risk and contribute to our understanding of community vulnerability were examined and evaluated. Changes in the residents' attitudes, cyclone preparednessbehaviours and willingness to respond to cyclone warnings were monitored and measured. Analysis of early survey data indicated that community residents generally had some knowledge of cyclones but a limited understanding of cyclone processes and very little direct personal experience of the cyclone hazard. Individually and collectively, residents frequently demonstrated a biased perception of the risks associated with cyclones. The resident community was shown to be fragmented, with limited support being available to individual households. Initially, residents were found to be poorly prepared for cyclones and unlikely to respond to warnings appropriately. It appeared that, in the event of a land-falling tropical cyclone impacting the area, the community was highly vulnerable to unnecessary loss of property, livelihood and – in extreme circumstances – life. By 2000, Cairns community residents were somewhat better informed about cyclones and certainly more experienced. This paper provides some insight into how cyclone experience and education may synergisticly have contributed to a change in risk perceptions and a reduction in the vulnerability of Cairns residents to the tropical cyclone and storm surge hazards.  相似文献