基于GIS的我国农村老年人口时空发展研究

以2000年、2003年、2006年和2009年4个时间点的农村老年人口数据为基础,从农村老年人口系数、老少比和养老负担3个指标对我国大陆31个地区的农村老年人口状况做了时间和空间上的对比分析。结果表明,农村老龄化发展迅速且从东部向中西部快速递进,农村老龄化的集中程度趋于降低。     

成都生态城市建设与大气环境质量的关系

通过对成都近5年的大气环境数据的分析,描述出其发展趋势,并找出其存在的主要问题与成因,在此基础上提出了以改善大气环境质量为中心的完善和促进成都建设生态城市的对策与途径.     

Psychosocial and Ergonomic Factors,and Their Relation to Musculoskeletal Complaints in the Swedish Workforce

A random sample of 1 000 subjects (20–65 years old) from the national population of Sweden received a questionnaire; 70% (n = 695) replied, of whom 532 were occupationally active. Female gender, working with neck and/or body bent forward, arms above shoulders, and precision work tasks were predictors of musculoskeletal symptoms. Neck, shoulder, and upper back symptoms were more common in a strained situation at work (high demands, low control) (adjusted odds ratios [adjOR] 2.76, 2.80, and 2.26, respectively). Among females, neck and shoulder symptoms were more common in an iso-strain situation (high demands, low control and low social support) (adjOR 4.43 and 3.69, respectively), and low back symptoms were more common at low social support combined with a passive work situation (adjOR 3.35). No associations were found between iso-strain model and symptoms among males. In conclusion, iso-strain work situation was associated with neck symptoms among females, even when controlling for ergonomic factors.     

有害物品运输的总风险分析

随着工业的发展,有害物品的生产量和运输量均在逐年增加,有害物品对环境和人的危害正在扩大和加深。有害物品运输中的风险是有害物品对于人类、环境和财产等方面威胁的最为重要的组成部分。笔者将有害物品的运输风险分为人口风险、环境风险和财产风险3个部分;在基于事故发生率和事故产生的后果两个方面,分别对人口风险、环境风险和财产风险进行了度量,并给出了风险度量的模型。同时由于各个部分风险度量的量纲并不统一,笔者对3部分风险进行了度量的统一化,获得了总风险的构成,并与传统的单独考虑人口风险的情况进行了对比,为有害物品的运输提供了参考依据。     

Effects of Restoring Oak Savannas on Bird Communities and Populations

Abstract:  Efforts to restore and maintain oak savannas in North America, with emphasis on the use of prescribed fire, have become common. Little is known, however, about how restoration affects animal populations, especially those of birds. I compared the breeding densities, community structure, and reproductive success of birds in oak savannas maintained by prescribed fire (12 sites) with those in closed-canopy forests (13 sites). All sampling was conducted in Illinois (U.S.A.). Of the 31 bird species analyzed, 12 were more common in savannas, 14 were not affected by habitat structure, and 5 were more common in forest habitat. The species favored by disturbance and restoration included Northern Bobwhites ( Colinus virginianus ), Mourning Doves (  Zenaida macroura ), Red-headed Woodpeckers (  Melanerpes erythrocephalus ), Indigo Buntings (  Passerina cyanea ), and Baltimore Orioles ( Icterus galbula ). Those more common in closed-canopy forest included Ovenbirds ( Seiurus aurocapilla ) and Wood Thrushes (  Hylocichla mustelina ). Few species were unique to one type of habitat, but overall avian community structure in oak savannas and closed-canopy forests was generally distinctive. Estimates of nesting success (derived from 785 nests) revealed that 6 of the 13 species considered experienced greater productivity in the savanna habitat. Rates of brood parasitism were unaffected by restoration and habitat structure. Within savannas, tract size had little effect on breeding abundances and reproductive success. My results illustrate that restoration techniques can significantly affect the ecology of constituent animal populations and communities and have key implications regarding avian conservation and the management of forest habitat in fragmented landscapes. Small patches of forest habitat that regularly function as population sinks may offer far better prospects for birds if they are subjected to disturbance and ecosystem restoration.     

Objectives for Multiple-Species Conservation Planning

Abstract:  The first step in conservation planning is to identify objectives. Most stated objectives for conservation, such as to maximize biodiversity outcomes, are too vague to be useful within a decision-making framework. One way to clarify the issue is to define objectives in terms of the risk of extinction for multiple species. Although the assessment of extinction risk for single species is common, few researchers have formulated an objective function that combines the extinction risks of multiple species. We sought to translate the broad goal of maximizing the viability of species into explicit objectives for use in a decision-theoretic approach to conservation planning. We formulated several objective functions based on extinction risk across many species and illustrated the differences between these objectives with simple examples. Each objective function was the mathematical representation of an approach to conservation and emphasized different levels of threat. Our objectives included minimizing the joint probability of one or more extinctions, minimizing the expected number of extinctions, and minimizing the increase in risk of extinction from the best-case scenario. With objective functions based on joint probabilities of extinction across species, any correlations in extinction probabilities had to be known or the resultant decisions were potentially misleading. Additive objectives, such as the expected number of extinctions, did not produce the same anomalies. We demonstrated that the choice of objective function is central to the decision-making process because alternative objective functions can lead to a different ranking of management options. Therefore, decision makers need to think carefully in selecting and defining their conservation goals.     

Influence of Forest Fragmentation on Community Structure of Frogs and Lizards in Northeastern Costa Rica

Abstract:  To better understand responses of reptiles and amphibians to forest fragmentation in the lowland Neotropics, we examined community and population structure of frogs and lizards in the fragmented landscape surrounding La Selva Biological Station in the Sarapiquí region of northeastern Costa Rica. We used diurnal quadrats and nocturnal transects to sample frogs and lizards in nine forest fragments (1–7 ha each) and La Selva (1100 ha). Species richness in all fragments combined was 85% of that found in La Selva with comparable sampling effort. Richness varied from 10 to 24 species among forest fragments, compared with 36 species at La Selva. Lizard density was higher and frog density was lower in forest fragments than in La Selva. Community composition varied among sites and by fragment size class, and species occurrence was nested with respect to fragment area. Isolation and habitat variables did not significantly affect species richness, composition, or nestedness. We classified 34% of species as fragmentation sensitive because they were absent or occurred at low densities in fragments. Nevertheless, the relatively high diversity observed in the entire set of fragments indicates that preserving a network of small forest patches may be of considerable conservation value to the amphibians and reptiles of this region.     

Losses of nitrogen and phosphorus from agricultural and forest areas in Finland during the 1980s and 1990s

The temporal changes and spatial variability of phosphorus andnitrogen losses and concentrations in Finland during the period1981–1997 were studied in 15 small agricultural and forestedcatchments. In addition, four coastal river basins with highagricultural land use located in southern Finland were includedin the study in order to assess the representativeness ofagricultural loss estimates from small agricultural catchments.The mean annual loss specific for agricultural land was estimatedto be on average 110 kg km^-2 a^-1 for total phosphorusand 1500 kg km^-2 a^-1 for total nitrogen. The resultsfrom small agricultural catchments were in agreement with thecorresponding loss estimates from rivers, with an average of137 kg km^-2 a^-1 for total phosphorus and 1800 kg km^-2a^-1 for total nitrogen. The results from the studiedagricultural catchments and rivers during the period 1981–1997suggest that weather-driven fluctuation in discharge was usuallythe main reason for changes in nutrient losses, and little or noimpact of changes in agricultural production or managementpractises can be observed. In forested areas the total phosphorusloss (average 9 kg km^-2 a^-1) and total nitrogen loss(average 250 kg km^-2 a^-1) were lower than inagricultural areas. In forested catchments the impact of forestryoperations, such as clear-cutting and fertilization, and theimpact of atmospheric nitrogen deposition can be seen in changesin nutrient losses.