Miyun County Research Articles

Gross ecosystem product accounting in Miyun County: the supply and use of ecosystem services

The ability of an ecosystem to provide services differs from its actual consumption and use by human society. Overuse of ecosystems can degrade ecosystems. In order to evaluate the supply capacity and use status of the ecosystem in Miyun County, so as to better apply the ecosystem services to different policies and management, the supply and use of 10 types of ecosystem services in Miyun County were calculated by using value indicators, namely potential gross ecosystem product (GEP) and actual gross ecosystem product. The results show that: (1) In 2020, potential gross ecosystem product of Miyun County is 254.32 billion yuan, and actual gross ecosystem product is 53.28 billion yuan, accounting for 21% of the potential gross ecosystem product. (2) Among all kinds of ecosystem services, the contribution of water conservation services in potential gross ecosystem product is the highest, and the contribution of climate regulation services in actual gross ecosystem product is the highest. (3) The contribution of wetland was the highest in potential gross ecosystem product, while the contribution of forest was the highest in actual gross ecosystem product. (4) Natural ecosystem area and vegetation coverage are the main factors affecting potential gross ecosystem product, while actual gross ecosystem product is mainly affected by GDP and population. (5) By studying the potential supply and actual use of ecosystem services, we evaluated and distinguished between the services that ecosystem could produce and the services that were actually used by humans, and compared the supply capacity and actual use to assess the sustainability of ecosystem services, in order to formulate different policies and management measures for gross ecosystem product surplus and deficit regions. Potential gross ecosystem product could provide data support for the assessment of ecological protection benefits. Actual gross ecosystem product could be included in the system of national accounts, and as a standard for ecological compensation and ecological trading. Confusing potential supply and actual use in policy application would affect the effect of policy implementation, and distinguishing them could ensure policy implementation. The relative size of the relationship between the two could reflect the present and future levels of human well-being in a region. Both together provided management basis and policy-making support for guiding regional ecological protection and sustainable development.

Estimating the Soil Erosion Response to Land-Use Land-Cover Change Using GIS-Based RUSLE and Remote Sensing: A Case Study of Miyun Reservoir, North China

Soil erosion by water is a major cause of land degradation. Agricultural practices and many other ecological environmental problems contribute to land degradation worldwide, especially in arid and semi-arid areas. Miyun County, which is located in a mountainous region of North China, is an important natural ecological zone and surface source of drinking water for Beijing and is very vulnerable to soil erosion due to its thin soil layer and human activities. Landsat images from 2003 and 2013 were used to analyze the land-use and land-cover change (LULCC) over this period. The revised universal soil loss equation (RUSLE) model integrated with Geographic Information System (GIS) was used to quantify soil loss and to map erosion risk. In addition, the response of soil erosion to LULCC was evaluated. The results showed that the areas under cropland, forest, and water bodies increased over the study period by 66.03, 243.44, and 9.01 km2, respectively. The increase in forested land indicated that the improved ground vegetation cover was due to the implementation of active ecological measures. Between 2003 and 2013, light soil erosion increased by 587.46 km2, and extremely severe soil erosion increased by 9.57 km2. The extents of slight, moderate, severe, and very severe soil erosion, however, decreased by 8.02, 445.21, 142.69, and 1.11 km2, respectively. A total of 57.5% of land with moderate soil erosion has been converted to light soil erosion, which could be highly beneficial for the improvement of vegetation control of soil and water losses. In terms of area, forestland exhibited the greatest increase, while moderate soil erosion exhibited the greatest decrease over the study period. Land-use change led to an alteration in the intensity of soil erosion due to changes or loss of vegetation. The conversion from high intensity soil erosion to low intensity was attributed to the implementation of ecological environmental protection. The results generated from this study may be useful for planners and land-use managers to make appropriate decisions for soil conservation.

Agricultural nitrogen flow in a reservoir watershed and its implications for water pollution mitigation

Miyun Reservoir plays a fundamental role in providing drinking water for Beijing Municipality. In this study, agricultural nitrogen (N) flow was analysed for water pollution mitigation in Miyun Reservoir watershed. A partial substance flow analysis (SFA) method was applied to evaluate the historic changes in N flow from 2001 to 2017. Based on this method, N flow, N losses, N accumulation, and nitrogen use efficiency (NUE) over 17 years were identified and quantified. The results showed that N input, N output, and N stock gradually decreased in this period. The decline of N input mostly resulted from the considerable decrease in chemical fertilizer use and livestock excrement application. With decreasing N input, the N stock also decreased over these years. The N losses generally decreased, except for 2009–2012, as a result of the substantial increase in harvested grains which generated even more straw for feeding or burning. In addition, the average NUE was as low as approximately 15% which may due to the huge straw storage and N losses. It is indicated that there was a great potential to decrease N input especially chemical fertilizer for mitigation of water pollution through analysis. Therefore, combined technology innovation with policy impact was proposed in Miyun County. Reducing chemical fertilizer, improving waste cycling, reducing ammonia volatilization, preventing erosion and runoff and improving peasant awareness of environmental protection were proposed as recommendations. The historic analysis of N flow could be helpful to understand the challenges of N pollution. The integrated policy and technology measures will be effective to achieve water quality control. Both will provide a reference for other countries or regions with the similar issues.

Association between muscle strength and health-related quality of life in a Chinese rural elderly population: a cross-sectional study

ObjectiveTo investigate the relationship between upper and lower limb muscle strength and the health-related quality of life (HRQoL) of a Chinese rural, elderly population.DesignA population-based, cross-sectional study.SettingMiyun, Beijing, China.ParticipantsThe participants...

Geospatial Analysis of Mass-Wasting Susceptibility of Four Small Catchments in Mountainous Area of Miyun County, Beijing.

Driven by the pull of gravity, mass-wasting comprises all of the sedimentary processes related to remobilization of sediments deposited on slopes, including creep, sliding, slumping, flow, and fall. It is vital to conduct mass-wasting susceptibility mapping, with the aim of providing decision makers with management advice. The current study presents two individual data mining methods—the frequency ratio (FR) and information value model (IVM) methods—to map mass-wasting susceptibility in four catchments in Miyun County, Beijing, China. To achieve this goal, nine influence factors and a mass-wasting inventory map were used and produced, respectively. In this study, 71 mass-wasting locations were investigated in the field. Of these hazard locations, 70% of them were randomly selected to build the model, and the remaining 30% of the hazard locations were used for validation. Finally, a receiver operating characteristic (ROC) curve was used to assess the mass-wasting susceptibility maps produced by the above-mentioned models. Results show that the FR had a higher concordance and spatial differentiation, with respective values of 0.902 (area under the success rate) and 0.883 (area under the prediction rate), while the IVM had lower values of 0.865 (area under the success rate) and 0.855 (area under the prediction rate). Both proposed methodologies are useful for general planning and evaluation purposes, and they are shown to be reasonable models. Slopes of 6–21° were the most common thresholds that controlled occurrence of mass-wasting. Farmland terraces were mainly composed of gravel, mud, and clay, which are more prone to mass-wasting. Mass-wasting susceptibility mapping is feasible and potentially highly valuable. It could provide useful information in support of environmental health policies.

Analysis of the triggering conditions and erosion of a runoff-triggered debris flow in Miyun County, Beijing, China

The occurrence of debris flow from channel-bed failure is occasionally noted in small and steeply sloping watersheds where channelized water flow dominates debris flow initiation. On August 12, 2016, a debris flow from channel-bed failures occurred in the Caozhuangzi Watershed of the Longtan Basin, Miyun, Beijing. Rainfall records over 10-min intervals and field investigations including channel morphology measurements were used to study the triggering conditions and erosion process. The results indicated that the occurrence of this event lagged the peak 10-min rainfall interval and that the cumulative rainfall prior to the occurrence time played an important role in its formation. A mean 10-min rainfall intensity–duration expression in the form of I10 = 5.0 × D−0.21, where I10 denotes the mean 10-min rainfall intensity and D is the rainfall duration ranging from 10 to 60 h, was proposed. The debris flows have low proportions of grain size fractions < 0.1 mm and higher fractions of grains 0.1–2 mm in size, indicating that the flow had low viscosity and was coarse-grain dominated. Channel morphology analysis revealed that abrupt changes in topography in the study area, including a steep section, a concave stream bank area, and a partial concave stream section were eroded more extensively than other sites. The maximum sediment erosion volume and erosion depth were not proportional to the variation in stream gradient. Consideration of the degree of erosion in the channel at sites with abrupt morphology changes, the maximum sediment erosion volume, and the erosion depth and volume at the initial channel site and downstream region of forest area together showed that the prime factor controlling erosion was entrained sediment volume. This work, thus, provides a case study regarding the triggering conditions of runoff-triggered debris flows and the topographical changes by debris flow erosion.

A simulation–optimization modeling approach for watershed-scale agricultural N2O emission mitigation under multi-level uncertainties

In this research, an integrated simulation–optimization modeling approach (ISOMA) was developed for supporting agricultural N2O emission mitigation at the watershed scale. This approach can successfully combine soil N2O emission simulation and the consequential mitigation management within a general modeling framework. Also, uncertainties associated with the key soil parameter can be effectively reflected and addressed through adoption of Monte Carlo analysis for the simulation results. The Monte Carlo simulated results were then used to generate fuzzy membership functions that can be consequentially used for emission mitigation management, reflecting the combined uncertainties for N2O emission simulation and mitigation management. The developed ISOMA was then applied to a reservoir watershed in Miyun county of Beijing municipality. In the studying watershed, the simulation model was calibrated and verified. Then, N2O emission from multiple agricultural land-use patterns were predicted. The amounts of N2O emission of four land use patterns (i.e., cash tree, orchard, cropland, and natural forest) were (536.9, 590.8, 653.1), (237.7, 254.4, 275.9), (79.5, 100.7, 105.1), (33.0, 47.3, 61.1) kg CO2 eq ha−1 year−1, respectively. Two scenarios (i.e., G1 and G2) were set up according to development priorities of local economy and society. Meanwhile, multiple credibility levels were considered according to the risk of N2O emission. The land use patterns could be adjusted according to solutions of ISOMA. The developed methods could help regional manager choose various production patterns with cost-effective agriculture N2O emission management schemes in the Miyun reservoir watershed. The manager also can obtain deeply insights into the tradeoffs between agricultural benefits and system reliabilities.

Identification of key patches for biodiversity conservation based on possibility of connectivity method

Abstract: The optimization of landscape structure will benefit for biodiversity conservation by analysing the best landscape layout as the habitat patches have been rapidly lost. Based on the possibility of connectivity (PC) method have been proposed for the assessment of biodiversity value that considered both habitat size and spatial connectivity, which regards the index of PC as its primary parameter. Miyun County, Beijing is studied as a case area to evaluate the biodiversity value by both the popular method and the proposed method. It is concluded that the total biodiversity value of each concerned land use types based on 2010 dataare: grazing land 3.69×106 Yuan•ha-1•year-1, forest land 132.39×106 Yuan•ha-1•year-1, cropland 5.65×106 Yuan•ha-1•year-1, water area 18.94×106 Yuan•ha-1•year-1, built-up land 0, and unused land 0.11×106 Yuan•ha- 1•year-1. Secondly, for the identification of key patches, there are three kinds of key patches: (1) the patches with larger habitat size; (2) the satellite patches around the large patches as the undertaken area for biologicalmigration; (3) the stepping stone patches. It is found that biodiversity value is not evenly distributed with patch area because of the difference of connectivity. Larger patches and the patches locate in the connecting position are important for maintaining connectivity. The results of this paper will provide technology and data references for environmental protection in the near future.

Regional Daily ET Estimates Based on the Gap-Filling Method of Surface Conductance

Remote sensing allows regional evapotranspiration (ET) values to be obtained. Surface conductance is a key variable in estimating ET and controls surface flux interactions between the underlying surface and atmosphere. Limited by the influence of clouds, ET can only be estimated on cloud-free days. In this study, a gap-filling method is proposed to acquire daily surface conductance, which was coupled into a Penman-Monteith (P-M) equation, to estimate the regional daily ET over the Hai River Basin. The gap-filling method is coupled with the canopy conductance, surface conductance and a simple time extension method, which provides more mechanisms and is more comprehensive. Field observations, including eddy covariance (EC) fluxes and meteorological elements from automatic weather station (AWS), were collected from two sites for calibration and validation. One site is located in Guantao County, which is cropped in a circular pattern with winter wheat and summer maize. The other site is located in Miyun County, which has orchard and summer maize crops. The P-M equation was inverted to the computed surface conductance at the field scale, and latent heat fluxes from EC were processed and converted to daily ET. The results show that the surface conductance model used in the gap-filling method performs well compared with the inverted surface conductance, which suggests that the model used here is reasonable. In addition, the relationship between the results estimated from the gap-filling method and EC measurements is more pronounced than that between the other method and the EC measurements. The R 2 values improve from 0.68 to 0.75 at the Guantao site and from 0.79 to 0.88 at the Miyun site. The improvement mainly occurs during the growing crop season, according to the temporal variations in the results.

The sources of trace element pollution of dry depositions nearby a drinking water source.

Miyun Reservoir is one of the most important drinking water sources for Beijing. Thirteen atmospheric PM sampling sites were established around this reservoir to analyze the mineral composition, morphological characteristics, element concentration, and sources of atmospheric PM pollution, using transmission electron microscope, X-ray diffraction, and inductively coupled plasma mass spectrometry analyses. The average monthly dry deposition flux of aerosols was 15.18g/m2, with a range of 5.78-47.56g/m2. The maximum flux season was winter, followed by summer, autumn, and spring. Zn and Pb pollution in this area was serious, and some of the sample sites had Cr, Co, Ni, and Cu pollution. Deposition fluxes of Zn/Pb in winter and summer reached 99.77/143.63 and 17.04/33.23g/(hm2 month), respectively. Principal component analysis showed two main components in the dry deposition; the first was Cr, Co, Ni, Cu, and Zn, and the other was Pb and Cd. Principal sources of the trace elements were iron mining and other anthropogenic activities in the surrounding areas and mountainous area north of the reservoir. Mineralogy analysis and microscopic conformation results showed many iron minerals and some unweathered minerals in dry deposition and atmospheric particulate matter, which came from an iron ore yard in the northern mountainous area of Miyun County. There was possible iron-rich dry deposition into Miyun Reservoir, affecting its water quality and harming the health of people living in areas around the reservoir and Beijing.

A holistic school-based nutrition program fails to improve teachers’ nutrition-related knowledge, attitudes and behaviour in rural China

Purpose– The purpose of this paper is to examine the effectiveness of a holistic school-based nutrition programme using the health-promoting school (HPS) approach, on teachers’ knowledge, attitudes and behaviour in relation to nutrition in rural China.Design/methodology/approach– A cluster-randomised intervention trial design was employed. Two middle schools were randomly selected and assigned to either the intervention school using the HPS framework (HPS School), or to the Control School, in Miyun County, Beijing. From each school 20 teachers were randomly selected to complete the survey. Nutrition-related knowledge, attitudes and behaviour were measured at pre- and post-intervention surveys with the same instrument. The nutrition intervention last for six months.Findings– The holistic school-based nutrition programme using the HPS framework had no statistical impact on improving teacher’s knowledge, attitudes and behaviour in relation to nutrition (p&gt; 0.05).Practical implications– Future holistic school-based nutrition programmes targeting adolescents should also design and implement longer and more intensive interventions for teachers focusing on how to equip them with the awareness and ability to disseminate their knowledge, positive attitudes and role model behaviours to students, rather than on how to teach them basic knowledge and skills.Originality/value– Although teachers play a critical role in the HPS framework, there is very limited published research investigating the change in teachers’ nutrition-related knowledge, attitudes and behaviour as a result of a nutrition promotion programme.

Study on incidence and risk factors of fall in the elderly in a rural community in Beijing

To investigate the incidence of fall in the old farmers of Miyun county in Beijing. The old farmers who lived in Jugezhuang and Fengjiayu townships of Miyun county were selected for a questionnaire survey to collect the information about the incidence of fall and their health status. A total of 2 397 old farmers, including 967 males and 1 430 females, were surveyed. Fall occurred in 347 old farmers(14.5%). The difference in the incidence of fall was significant between males(9.6%)and females(17.8%). A total of 282 falls occurred in courtyards, 45 falls occurred in field/hilly areas. Among the falls occurred, 216(27.2%)led to injuries. The most common site of injuries was hip(45 falls). Logistic regression analysis showed that physical exercise and high income were protective factors, but difficult standing up and walking, visual problem and stroke were the risk factors. In the males, the special risk factor was mid cognitive impairment, and in the females, the special risk factor was urinary incontinence, but afternoon nap was a protective factor. The incidence of fall in the rural community was relatively high with distinct area distribution, which has caused serious influence on the mental and physical health of the elderly.

Effect of interventions to improve adolescents’ nutrition knowledge in China

Purpose – The purpose of this paper is to improve adolescents’ nutrition knowledge and to examine the effect of interventions component to improve adolescents’ nutrition knowledge. Design/methodology/approach – The study design was multi-factorial with repeated measures, at two points in time, of dependent samples from three schools, which were randomly selected from 15 middle schools in Miyun County, Beijing, and then randomly assigned to control school or intervention school. The instrument for baseline survey was a 14-item and for follow-up survey was a 26-item, self-administered, structured questionnaire, designed in Chinese. Findings – Students’ nutrition knowledge improved significantly in intervention schools after intervention compared with controls. The extent to which students felt that peer support activities were helpful and that what they learned in class about nutrition was helpful, was related to their resultant level of nutrition knowledge. Originality/value – To the authors’ knowledge there have been no previous studies which explore the effect of specific intervention components on levels of nutrition knowledge among adolescents.

Residues and Sources of DDT and HCH in Agricultural Soils in the Suburb of Beijing, China

Abstract. Twenty-five topsoil samples (0-20cm) were collected to determine the dichlorodiphenyltrichloroethane (DDT) and its metabolites, isomers of hexachlorocyclohexane (HCH) residues from the agricultural soil in the Miyun County. The average measured concentrations of HCH and DDT were 1.07±0.84 and 6.54±7.88 ng·g-1, separately (dry weight; n=25; shown as arithmetic mean and standard deviation), which were lower than most of the results reported in literatures. Both of the detectable rates of HCH and DDT were 100％ and the residual levels was lower than most of other Chinese region．According to the values of isomers ratios, it show that HCH mainly from residues, therefore there were still new sources of DDT which entered into the soil of the studied area.

Endogenous derivation of optimal environmental policies for proper treatment of stockbreeding wastes in the upstream region of the Miyun Reservoir, Beijing

AbstractStockbreeding industries are increasing rapidly in rural areas around big cities in China. This increase carries high risks to the environment due to emissions of large amounts of water pollutants and greenhouse gases. On the other hand, stockbreeding wastes are a typical biomass resource and can be used as an energy source by advanced technologies. In this study, we selected Miyun County and focused on analysing the synthetic environmental policies as endogenous variables by computer simulation including the introduction of advanced technologies to improve the environment and provide more biomass energy. The model considered both the total ecological system and the socio‐economic situational changes. The purpose of our research is to establish effective utilization methods for biomass resources as well as co‐ordinate resource reutilization, environmental preservation and economic development, and finally realize sustainable development of the society.

Identification of key factors governing chemistry in groundwater near the water course recharged by reclaimed water at Miyun County, Northern China

Reclaimed water was successfully used to recover the dry Chaobai River in Northern China, but groundwater may be polluted. To ensure groundwater protection, it is therefore critical to identify the governing factors of groundwater chemistry. Samples of reclaimed water, river and groundwater were collected monthly at Chaobai River from January to September in 2010. Fifteen water parameters were analyzed. Two kinds of reclaimed water were different in type (Na-Ca-Mg-Cl-HCO3 or Na-Ca-Cl-HCO3) and concentration of nitrogen. The ionic concentration and type in river were similar to reclaimed water. Some shallow wells near the river bed had the same type (Na-Ca-Mg-Cl-HCO3) and high concentration as reclaimed water, but others were consistent with the deep wells (Ca-Mg-HCO3). Using cluster analysis, the 9 months were divided into two periods (dry and wet seasons), and all samples were grouped into several spatial clusters, indicating different controlling mechanisms. Principal component analysis and conventional ionic plots showed that calcium, magnesium and bicarbonate were controlled by water-rock interaction in all deep and some shallow wells. This included the dissolution of calcite and carbonate weathering. Sodium, potassium, chloride and sulfate in river and some shallow wells recharged by river were governed by evaporation crystallization and mixing of reclaimed water. But groundwater chemistry was not controlled by precipitation. During the infiltration of reclaimed water, cation exchange took place between (sodium, potassium) and (calcium, magnesium). Nitrification and denitrification both happened in most shallow groundwater, but only denitrification in deep groundwater.

Use of a no prism total station for field measurements in Pinus tabulaeformis Carr. stands in China

A Pentax R-422N no prism total station was used to improve data quality, survey efficiency and contributed to crown volume study in field measurements of forestry resources. The study was conducted through field measurements in Chinese Pine, Pinus tabulaeformis Carr. (Pinaceae) stands in Beijing, Miyun County of China. The data included independent tree variables, such as three-dimensional coordinate, tree height, diameter at breast height (DBH), and crown width. Compared with control values which were approximate to values obtained by a research team composed of skilled surveyors, the results indicated that three-dimensional coordinate, tree height, DBH, and the crown width of each tree can be measured to a high precision using a no prism total station in less than 1 min. The relative error of tree height was 90%, which means measurement quality objectives (MQOs) adopted in the Forest Inventory and Analysis Programme (FIA) of the USDA Forest Service were achieved. Crown volume calculation and three-dimensional modelling by using 3D-MAX were practiced out with reliable data acquired by the no prism total station. The results can be used in different tree growth studies and for the assessment of forest volume and biomass in China.

Research of the Response of Ecosystem to LUCC in Miyun County, Beijing: Based on Ecosystem Services Valuation

Abstract Miyun County, located in the northeast of Chinese capital Beijing, was underwent remarkable variations in land use in recent years. This paper aimed to detect changes in land use of Miyun from 1997 to 2005, and to qualify the response of ecosystem to LUCC based on ecosystem services valuation. With two-periods TM images, we got land use change data, and then ecosystem services values were calculated using ecosystem services valuation coefficients proposed by Chinese scholar Xie Gaodi. Results showed that water area, farm land and unused land decreased while residential land, forest land, grassland and orchard land increased during the study period. The loss of ESV was RMB 206 million and the main reason was the decrease of water area and farm land area. As for spatial variation, there were most dramatically land use change and ESV decline in reservoir ecological protection region. The coefficient sensitivity analysis indicates that valuation coefficients used in the study are suitable and results...

北京城市绿地的蒸腾降温功能及其经济价值评估

PDF HTML阅读 XML下载 导出引用 引用提醒 北京城市绿地的蒸腾降温功能及其经济价值评估 DOI: 10.5846/stxb201203150345 作者: 作者单位: 中国科学院 地理科学与资源研究所,环保部 南京环境科学研究所,中国科学院 地理科学与资源研究所,中日友好环境保护中心 作者简介: 通讯作者: 中图分类号: 基金项目: 环保公益性行业科研专项(201209027);中国科学院地理科学与资源研究所"一三五"战略科技计划项目(2012ZD007) Preliminary evaluation of air temperature reduction of urban green spaces in Beijing Author: Affiliation: Institute of Geographical Sciences and Natural Resources Research,Chinese Academy of Science,Nanjing Institute of Environmental Sciences of the State Environmental Protection Administration of China,Institute of Geographical Sciences and Natural Resources Research,Chinese Academy of Science,Sino-Japan Friendship Center for Environmental Protection Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:尽管已有大量研究证实,城市绿地具有明显降温作用,但是从生态经济学角度定量评估城市绿地降温功能及其价值的研究不多。以夏季高温热害显著的北京建成区为研究区,在前人多项绿地降温功能实测结果基础上,利用第七次园林绿地资源调查数据,定量评估了城市绿地夏季蒸腾降温的功能及其价值。结果表明:北京建成区6.1万hm2 绿地每年夏季蒸腾吸热可达4.61×1015 J,平均每公顷绿地每天吸热8.4×108 J,相当于10台1000瓦空调的降温作用。参照居民用电价格,建成区绿地夏季降温价值为6.4亿元,单位绿地降温价值约1.05元/m2。此外,不同绿地类型和区县绿地的降温功能差异较大,主要受绿地面积和组成结构的影响。 Abstract:Climate change is the most serious problem we face in the 21st century. Accompanied by the rapid expansion of cities worldwide, the phenomenon of urban heat islands has become a critical environmental issue in many large cities, since it is associated with a warmer climate. An exposure to higher temperatures can result in a spectrum of outcomes in the realms of human health and well-being. These outcomes range from mild discomfort to life-threatening medical conditions. Fortunately, trees and vegetation in the urban environment help to cool urban climates. This occurs through shading and evapotranspiration. Although there have been numerous studies on microclimate-adjusting effects of urban green spaces, few of these studies quantify the economic value of air temperature reduction provided by these spaces. This is especially true for cities suffering from the heat island effect. Urban heat island conditions have been observed for more than half a century in the city of Beijing. The area affected by this heat island rapidly expanded from 111 km2 in 1987 to 292 km2 in 2009, and the percentage of heat island to built-up area increased sharply from 11% to 27%. Therefore, it is very important for city managers to estimate and achieve economic benefits of the cooling effect of green spaces. Based on a number of empirical studies and inventory data concerning urban green spaces in Beijing (2009), this study estimates the economic effects of the city's green space on air temperature reduction through evapotranspiration. The results show that green areas in Beijing could reduce the temperature by 0.8-4.8℃. As a consequence, urban green spaces totaling 6.1×104 hm2 in built-up areas of the city could absorb 4.61×1015 J of heat via evapotranspiration during summer. The average heat absorbed by these spaces could reach 8.4×108 J·hm-2·d-1, which corresponds to the cooling effect of ten 1000-W air conditioners. According to the price for residential electricity, the summer temperature reduction from the urban green spaces could save 641 million RMB of the cost of electric energy consumption per year. This figure is based on annual average savings reaching 1.05 RMB/m2 for urban green area with temperature reduction. In addition, the temperature reduction effects of urban green spaces varied with type and location. The amount of heat absorption of protected green zones was significantly less than those of public, roadside, affiliated, and productive green spaces. Average values of air temperature reduction per unit area of green space in Dongcheng District, Xicheng District, Miyun County, and Yanqing County were significantly higher than those of the districts of Pinggu, Fengtai and Shijingshan. These cooling effect variations may be related to differences in area and structure of urban green spaces. Therefore, evidence is provided to support the commitment of resources to urban green infrastructure enhancements. Furthermore, such evidence conveys the importance of the structural characteristics of green land. Urban foresters, ecologists, and landscape planners should take advantage of this type of data to plan, design and manage green spaces in heat island areas. In this way, communities can realize energy savings, and cities and urban neighborhoods can be made more livable. 参考文献 相似文献 引证文献

Testing for adverse selection of crop insurance in northern China

PurposeThe purpose of this paper is to examine the efficiency of current subsidized crop insurance products (SCIPs) in Miyun county, in northern China, by testing the existence of adverse selection.Design/methodology/approachThe authors examine the efficiency of SCIPs from a farmers' point of view by testing the existence of adverse selection using nonparametric tests and logit regression on data from individual interviews in Miyun County. Due to adverse selection, producers with more risk should be more likely to buy crop insurance in pursuit of the benefits from SCIPs.FindingsHowever, both methods conclude no existence of adverse selection, which indicates that the programs are inefficient. This may not be surprising based on the issues of concern cited above. The opportunities and challenges of a growing interest in weather index insurance are discussed toward the end of the paper.Originality/valueThis paper weaves together literature on traditional and weather index insurance, along with primary data from a survey, to examine the pros and cons of each type of insurance. Implications for policy makers are to compare the tradeoffs between concerns of the two types of insurance examined here, traditional and weather index insurance. Ultimately, the political goals might best determine which option is most desirable.