黄土丘陵区纸坊沟流域近70年农业生态安全评价

在国内外已有研究的基础上,结合黄土丘陵区纸坊沟流域近70a来农业生态经济系统演变过程,参考PSR模型,从生态环境、社会经济和综合功能3方面构建黄土丘陵区流域农业生态安全评价指标体系,基于层次分析法赋权的综合指数评价方法,对纸坊沟流域1938～2005年农业生态安全状况进行评价.结果表明:该流域农业生态安全状况发生了先降后升的变化,1938年处于较安全状况,1958年为极不安全状况,1975年和1985年都处于较不安全状况,1995年处于临界安全状况,2005年属于较安全状况.评价结果表明纸坊沟流域还需要进一步优化农业系统结构,实现农业生态安全.     

京津风沙源区沙障固沙技术评价指标体系构建

由于构成材料、规格形状以及自然风向和地貌形态的多样性,不同沙障固沙技术的固沙效果有较大差异,如何科学客观的筛选沙障固沙技术,是保证沙障固沙技术长期稳定发挥其最大作用的重要基础。针对京津风沙源区沙障固沙技术效果评价问题,建立了沙障固沙技术评价的方法体系,明确了沙障固沙技术评价指标集、评价指标权重以及沙障固沙技术评价面临的问题。在沙障固沙技术与地区自然条件、经济发展水平相协调的前提下,基于文献频次法和层次分析法(analytic hierarchy process,AHP)从技术成熟度、技术应用难度、技术相宜性、技术效益、技术推广潜力5个方面共筛选出1项判断性指标、4项准则性指标、14项二级指标和25项三级指标指标,构建沙障固沙技术评价指标体系。该指标体系以技术效益为主导,兼顾功能性和应用性综合评价,从而对京津风沙源区沙障固沙技术进行全面评价。     

四川短尾鼩尿液气味在社会等级识别中的作用

本文在中立竞技场中通过两两互作确定四川短尾鼩(Anourosorex squamipes)同性个体间的社会等级,并在此基础上利用其尿液,研究不同社会等级个体的自我或非自我识别能力及模式、尿液气味的行为响应机制,以及社会等级识别能力。结果表明:(1)四川短尾鼩优势个体表现攻击行为较多,从属个体防御行为较多,优势个体的标记行为显著高于从属个体;攻击行为表现为同等级雄性高于同等级雌性,且雌性间的攻击强度低于雄性;(2)从属个体和优势个体分别对自身尿液气味和非自身尿液气味存在明显偏好差异;不同性别、等级个体自我识别模式差异不明显,不同社会等级个体对于自身识别模式和非自身尿液的行为反应模式均不同。不同社会等级个体具有自我识别能力且能力不同;(3)四川短尾鼩能够识别不同社会等级个体的尿液气味,雌性对雄性尿液更感兴趣,雄性对优势雄性尿液选择回避;雄性对其他个体的访问时间与嗅舔频次均显著高于雌性,雌雄个体在识别不同社会等级的尿液气味时存在性二型。     

Evolutionary Psychology – Towards a More Integrative Model

Aspects of the history of behavioural science are reviewed, pointing to its fragmented and faction-ridden nature. The emergence of evolutionary psychology (EP) is viewed in this context. With the help of a dual-layered model of behavioural control, the case is made for a more integrative perspective towards EP. The model's application to both behaviour and complex human information processing is described. Similarities in their control are noted. It is suggested that one layer of control (‘on-line’) corresponds to the encapsulated modules of EP whereas the off-line controls provide the plasticity and flexibility suggested by its critics.     

Behavioral aspects of cold tolerance in blackchin tilapia,Sarotherodon melanotheron,at different salinities

Synopsis Cold tolerance and behavioral responses of blackchin tilapia, Sarotherodon melanotheron, to rapidly decreasing temperatures were investigated at salinities of 5, 15, and 35 parts per thousand (ppt). Cold tolerance did not significantly differ with salinity or social rank. Mean temperatures were 10.7° C for beginning loss of equilibrium, 9.6° C for complete loss of equilibrium, and 6.9° C for death at all salinities. Behavioral activity declined with decreasing temperature and ceased between 10–12° C. Certain behavioral actions were significantly more frequent at 15 or 35 ppt salinity than at 5 ppt. The northward range expansion by introduced populations of the blackchin tilapia in the United States probably will be limited by its lower lethal temperature limits, but may also be affected by temperatures at which social behavior becomes disrupted.     

Structure and Dynamics in an Urban Landscape: Toward a Multiscale View

Ecosystems and city systems often form hierarchically structured landscapes whose spatial pattern is scale dependent. While trends in the upper tail of national city-size distributions leave the impression that fractal-scaling laws such as Zipf's law or the rank-size rule truly represent the essence of the system, the linearity depicted at aggregate scale actually obscures variation and discontinuity in the urban size-density function, including multimodalities evident in regional data sets. Tracing individual city trajectories through these hierarchical patterns reveals structural resilience at macroscopic scale, the punctuated growth of individual cities of differing sizes, the persistence and self-reinforcing character of spatial agglomeration, and a general need for further empirical investigation of the relationship between city size and growth. It also raises questions for future exploration, including the meaning of persistent departures from the power laws of traditional urban systems theory. Interpretation of such departures in the context of questions of jurisdictional scale in environmental management and “smart growth” policy adds a practical dimension to the research agenda. Received 14 November 2000; accepted 5 September 2001.     

The Cell Biology of Antigen Processing

Abstract

T lymphocytes recognize antigen only after a series of intracellular events known as antigen processing. The result of antigen processing is the production of short segments of the primary peptide sequence bound to a polypeptide-binding groove on major histo compatibility complex (MHC) molecules. Antigen originates from one of two sites: intracellular or extra cellular. There are two corresponding pathways for antigen processing and two corresponding classes of MHC molecule. Analysis of each pathway has demonstrated that their separation is not purely anatomical, but is maintained by molecular interactions with other molecules. Antigen processing has been shown to regulate the overall immune response, but the mechanisms involved remain obscure.     

Changes in woody community structure and composition under constrasting landuse systems in a semi-arid savanna, South Africa

We aimed to explore the farm scale effects of three landuse types, communal grazing, wildlife management and commercial cattle farming, on the woody vegetation of a semiarid savanna. Location The study farms were located within a single bioclimatic zone in semiarid savanna, South Africa. Methods The species composition and structure of woody vegetation on three farms of each of three landuse types were sampled. Results We found that communal grazing land sites were classified outside the topland-bottomland vegetation dichotomy characteristic of this region. Comparisons of size class distributions showed the communal grazing lands had fewer small and large individuals; suggesting both lower levels of regeneration and regenerative capacity in the communal grazing lands. The species richness and biomass of woody plants was lower on communal grazing lands than on private game reserves and commercial cattle farms. The longevity of tree species explains the observed lag between changes in abundance and species loss; we consequently predict that there will be future losses of species in the communal grazing lands. By classifying species into a range of use-categories we showed that utilization and species loss was not limited to certain plant use categories. Higher levels of wood harvesting measured in the communal grazing lands are likely to be responsible for the observed differences. Main conclusions It is concluded that communal grazing management at this study site has substantially changed the composition and structure of woody plant communities, and that these changes have reduced the current availability of natural resources and will reduce resource production in the future.     

Measures of giant panda habitat selection across multiple spatial scales for species conservation

Examining ecological processes across spatial scales is crucial as animals select and use resources at different scales. We carried out field surveys in September 2005, March–September 2006, and April 2007, and used ecological niche factor analysis to determine habitat preferences for the giant panda (Ailuropoda melanoleuca) across 4 spatial scales: daily movement, core range, home range, and seasonal elevational migration. We found that giant pandas prefer conifer forest and mixed forest at higher than average elevation (2,157 m) of study area in the 4 scale models. However, we also observed significant scale differences in habitat selection. The strength of habitat preference increased with scale for the 2 disturbed forests (sparse forest and fragmented forest), and decreased with scale for 0–30° gentle slope and south- and north-facing aspect. Furthermore, habitat suitability patterns were scale-dependent. These findings highlight the need to determine species–environment associations across multiple scales for habitat management and species conservation. © 2012 The Wildlife Society.