Cycling In Urban Areas Research Articles

The effects of tree characteristics on rainfall interception in urban areas

Trees in urban areas have significant effects on the urban ecosystem. They can be used to improve the water cycle in urban areas by increasing evaporation and reducing runoff through rainfall interception. Street trees placed in planters on impervious areas reduce runoff by intercepting rainfall and by temporarily storing raindrops on leaves. Therefore, understanding tree canopy geometry and the effect of rainfall interception is important in urban hydrology. In this study, we assessed the effect of tree canopy morphology on rainfall interception using four major street tree species, Sophora japonica L., Ginkgo biloba L., Zelkova serrata (Thunb.) Makino, and Aesculus turbinata Blume, in Seoul, South Korea. We measured throughfall for each tree and also derived three-dimensional data of tree canopy morphology with a terrestrial laser scanner. Tree height, canopy crown width, leaf area index (LAI), leaf area density, mean leaf area, and mean leaf angle were used to determine canopy morphology. The interception rate was mostly affected by the LAI; a higher LAI tended to result in a higher interception rate. Leaf area affected the rainfall interception rate when trees had similar LAIs. These findings on individual tree canopy rainfall interception can help us to understand the importance of rainfall interception in hydrology and for ecological restoration when planning urban green spaces.

Calibração do modelo de consumo de combustível do simulador AIMSUN com dados coletados via OBD

Dados coletados por meio da interface de diagnóstico de bordo (On-Board Diagnostics ‒ OBD), presente nos automóveis nacionais fabricados a partir de 2009, foram usados na calibração de modelo microscópico de consumo de combustível do simulador AIMSUN. Para a calibração dos parâmetros do modelo de consumo, mediu-se a velocidade instantânea, o fluxo de ar de admissão e o teor de oxigênio na mistura ar/combustível. Calibrou-se o modelo de consumo do simulador seguindo a abordagem modal, usando regressão para os modos de aceleração e velocidades constantes e média simples para os modos de marcha lenta e desaceleração. Para validar o modelo, os consumos de combustível medido e estimado foram comparados em ciclos de condução em áreas urbanas. Os resultados indicam a adequação do método para avaliação do consumo de combustível por veículos em malhas viárias urbanas. Além disso, o modelo calibrado com dados do OBD de quatro tipos de veículos foi usado no estudo por simulação de cenários atual e futuro no contexto de projeto de ampliação viária. Por meio de abordagem comparativa entre cenários, mostra-se que a estimação com parâmetros calibrados produz indicadores distintos e mais confiáveis em relação aos obtidos com os parâmetros originais do simulador.

Realizing the opportunities of black carbon in urban soils: Implications for water quality management with green infrastructure

Soils and associated microbial processes regulate the carbon cycle and provide a sink for atmospheric black carbon (BC). Particularly in urban areas, present and accumulated soil BC may act as an effective sorbent of anthropogenic contaminants in green spaces. We characterized carbon concentrations that have accumulated in urban soils (organic carbon, BC, and inorganic C) and determined soil physical attributes (soil texture, hydraulic conductivity) from urban soil assessments (surface and sub-surface horizons) carried out in eleven cities in the United States. We used both ordinary least squares and non-parametric classification and regression tree (CART) methods to discern trends in soil BC concentrations with regard to soil, landscape, and emission characteristics. We found that for all cities, regional traffic density and vegetation were good predictors of soil BC concentration. Additionally, the thickness of the top soil horizon explained additional variation in sub-surface BC concentrations. Sites with coincident BC stocks and favorable infiltration rate were discussed as per their potential for improving water quality in multifunctional green infrastructure installations. In the broader sense, the high sorption capacity of existing, accumulated soil BC can contribute to regulation of contaminant cycling in urban areas and may enhance the overall value of urban soils in terms of ecosystem services.

Temporal consistency between gross primary production and solar-induced chlorophyll fluorescence in the ten most populous megacity areas over years

The gross primary production (GPP) of vegetation in urban areas plays an important role in the study of urban ecology. It is difficult however, to accurately estimate GPP in urban areas, mostly due to the complexity of impervious land surfaces, buildings, vegetation, and management. Recently, we used the Vegetation Photosynthesis Model (VPM), climate data, and satellite images to estimate the GPP of terrestrial ecosystems including urban areas. Here, we report VPM-based GPP (GPPvpm) estimates for the world’s ten most populous megacities during 2000–2014. The seasonal dynamics of GPPvpm during 2007–2014 in the ten megacities track well that of the solar-induced chlorophyll fluorescence (SIF) data from GOME-2 at 0.5° × 0.5° resolution. Annual GPPvpm during 2000–2014 also shows substantial variation among the ten megacities, and year-to-year trends show increases, no change, and decreases. Urban expansion and vegetation collectively impact GPP variations in these megacities. The results of this study demonstrate the potential of a satellite-based vegetation photosynthesis model for diagnostic studies of GPP and the terrestrial carbon cycle in urban areas.

Responses of urban heat island in Atlanta to different land-use scenarios

The urban heat island (UHI) effect changes heat and water cycles in urban areas, and has been accused of elevating energy consumption, deteriorating living environment, and increasing mortality rates. Understanding various UHI effects necessitates a systematic modeling approach. A major problem in UHI simulations is that urban areas were either considered to have only one category of land use/cover or outdated in land use/cover patterns due to the lack of high resolution data. Therefore, this study aims at integrating up-to-date remotely sensed land use/cover data with the Weather Research and Forecasting (WRF/UCM)/Urban Canopy Model modeling systems to simulate surface temperature patterns in Atlanta, Georgia. In addition, three land-use scenarios, i.e., spontaneous scenario (SS), concentrated scenario (CS), and local policy scenario (LPS), were designed and incorporated into the modeling. Five numerical experiments were conducted by using the Weather Research and Forecasting (WRF) model to explore the impact of urbanization-induced land-cover changes on temperature patterns. Land use and land-cover patterns under all three scenarios suggested that urban growth would continue through in-filling development and outward expansion. Compared to temperature simulations in 2011, temperature maps corresponding to the three urban growth scenarios showed warmer and cooler temperature patterns outside and inside the urban core, respectively. Analysis of the mean diurnal temperature cycle suggested that the highest temperature difference of 3.9 K was observed between 2011 and the LPS, and occurred around 22:00 local time. Overall, the simulations showed different UHI effects respond to the land-use scenarios in the summer. It is recommended for urban managers and policy makers to reflect on the potential impacts of alternative urban growth policies on thermal environment.

Shared Use Routes for People Who Walk or Cycle: Addressing the Challenges

Background Active travel (particularly walking and cycling) in urban environments is promoted for public health benefits and as a means of reducing motorised traffic. Walking is the most popular and inclusive form of active travel. In many urban areas, completely segregated space for cycling can be difficult to accommodate. This, combined with perceived dangers of sharing roads with motorised traffic, can act as barrier to cycling uptake. A solution has been to designate some paths as shared use. In Bristol this has led to some conflict between pedestrians and cyclists. In particular, older and disabled pedestrians can feel unsafe on shared use routes. Methods In preparation for a larger research bid, we undertook a social media campaign (mid-Feb to mid-Mar 2016). We encouraged pedestrians and other users to pinpoint shared spaces on a map of Bristol and insert a comment about the shared use. In addition, a researcher went out to community groups to help with use of the map (including taking paper maps) and/or collect verbal information about shared spaces. Results 427 points with comments were submitted from across the city. On-line use of the map focused on more central areas and cycling routes further out of the city (approx. 50% of responses). Researcher assistance generated comments from both inner city and outer neighbourhood groups with an emphasis on the elderly and people with disabilities (approx. 50% of responses). The Framework method was used to assist data analysis. All comments were entered into a chart and the text was coded as issues were identified. Five key themes emerged: space, speed, surfaces, signage and social behaviour. Space issues included: path widths, positioning of street furniture and dangerous pinch points. The speed of motorised traffic on roads, and cyclists on shared pathways, created feelings of vulnerability and tension for the slower user. Uneven surfaces and inconsistent design lead to discomfort and confusion for both pedestrians and cyclists. Signs are often unclear about who has priority and which areas are for pedestrians or cyclists. Much greater awareness of the social etiquette for shared use is required. Conclusions Walking and cycling in urban areas require appropriate infrastructure. Where shared use is a design solution, it should be considered from the perspective of a variety of users. Space, speed, surfaces and signage can all contribute to conflict between users. Clear guidance relating to behaviour on shared use routes is required and should be promoted.

Phosphorus cycling in urban aquatic ecosystems: connecting biological processes and water chemistry to sediment P fractions in urban stormwater management ponds

Phosphorus (P) dynamics in urban landscapes may differ from that in natural landscapes due to different P sources and unique environmental conditions. However, many aspects of P cycles in urban areas, especially within engineered aquatic ecosystems, remain largely unknown. Through this work, we aim to contribute to better understanding of P cycling in urban aquatic ecosystems by investigating P fractions in sediment and their relationship with ambient chemistry in surface water from six urban stormwater management ponds located in Ontario, Canada. We found that organic P contributed up to 75% of total P in pond sediment, but this percentage decreased significantly between our two sampling events in June and September 2012. This decrease coincided with increased rates of extracellular enzyme (especially phosphatase) activities, which is indicative of fast mineralization processes in these ecosystems. Moreover, the decreased sediment organic P was matched by increased water column P concentration. This inverse relationship suggests that the large organic P pool in pond sediment, and its fast decomposition, contributed to internal release of P from sediment and increased water column P concentrations. The dominance of organic P in sediment and the putative role of relevant biological processes (i.e., decomposition and productivity) in urban ponds found in this study strongly contrast with classic water management expectations of physicochemically controlled P dynamics and long-term P storage in sediment of aquatic ecosystems. This difference suggests that urban stormwater ponds may perform poorly in terms of P retention and thereby contribute to poor water quality in terms of P pollution to downstream urban watersheds. Thus, stormwater pond design and future management strategies should consider these biogeochemical features of urban ponds, including internal P release, to help prevent eutrophication of downstream ecosystems.

Metabolism-based modelling for performance assessment of a water supply system: a case study of Reggio Emilia, Italy

A new class of conceptual simulation tools, as a complement to physically based models, is becoming available to simulate the whole water cycle in urban areas for strategic planning, often involving the allocation of a great amount of financial resources. These simulation tools are required to estimate the impact of the today's decisions on the system performance over the next decades and to compare and rank different intervention strategies. To achieve this, this paper aims to build the metabolism-based modelling of a real water supply system using the recently developed WaterMet2 model in order to evaluate long-term performance metrics for possible intervention strategies. This metabolism-based approach was demonstrated for evaluation of the water supply system of Reggio Emilia, Italy, which is one of the demonstration case studies in the EU TRUST (TRansitions to the Urban water Services of Tomorrow) project. Based on the strains imposed by pressing challenges (here population growth) two intervention strategies were analysed. The results obtained show that the built and calibrated WaterMet2 model allows a broader understanding of the impacts of alternative intervention strategies taking into account multidimensional aspects of the sustainability beside conventional service performance.

Copro-necrophagous beetles (Coleoptera: Scarabaeinae) in urban areas: A global review

The world has become an urban world, more than 50 % of the human population live in cities. The effects of urbanization are diverse, complex and wide; ranging from unbalanced biogeochemical cycles in urban areas, to the local extinction of several species in different cities around the globe. However, diverse biological groups live and thrive in cities adapting to the new and sometimes harsh conditions of urban areas. In an effort to compile and assess the current status of knowledge of copro-necrophagous beetles in urban areas, we performed an extensive search for publications regarding Scarabaeinae beetles in urban areas. We found 27 publication that address four general topics: (1) ecological patterns; (2) disease transmission; (3) conservation biology; and (4) species lists. Although in the last fifteen years it has been published extensively about Scarabaeinae as an indicator group in biodiversity studies and in the analysis of ecosystem functions, references to Scarabaeinae in cities are scarce. In a broad sense, the study of copro-necrophagous beetles in urban areas is in an early stage of advance, providing an opportunity for entomologists to explore their response to urbanization, altogether with the role of these insects as host and intermediates of parasitic diseases, but also, with the environmental services provided by them, like the burial and destruction of a great amount of excrements found in urban soil.

THE RELATIONSHIP BETWEEN STREET NETWORK MORPHOLOGY AND PERCENTAGE OF DAILY TRIPS ON FOOT AND BY BICYCLE AT THE CITY-LEVEL

There are various factors that affect walking and cycling in urban areas, such as density, diversity and design, but there have been few studies that examine the relationship between urban morphology factors such as street network and green travel modes (e.g., walking and cycling) at the city-level (macro-level). Thus, this paper focuses on this relationship by introducing street network morphology factors, such as blocks per area, nodes per blocks and nodes per area. The street network in this study includes interconnecting lines and points that present streets, roads, motorways, intersections and blocks. The percentage of daily trips on foot and by bicycle data that represents walking and cycling are collected from the International Association of Public Transport’s (UITP) database. The blocks per area, nodes per area and the nodes per blocks are estimated by modifying and analyzing Open Street Maps (OSM). The data that are used in this study are from 30 cities in different parts of the world. The strength of the relationship in this study was found using the Pearson correlation coefficient. The results show that increase in daily trips on foot and by bicycle is correlated with increasing number of blocks per area and number of nodes per area while daily trips on foot and by bicycle has negative relationship with number of nodes per blocks. Because the urban street network is the result of macro-scale planning decisions, considering the relationship between street network morphology and travel behavior can lead to better planning decisions.

Impervious surface extraction in urban areas from high spatial resolution imagery using linear spectral unmixing

Impervious surface, as an important indicator of urbanization assessment, plays a significant role in analyzing the climate, environment and hydrologic cycle in urban areas. Impervious surface extraction in urban areas from satellite imagery attracts growing attention in many applications. Recently, the increasing availability of high spatial resolution satellite imagery provides new opportunities for impervious surface extraction at a fine scale. However, impervious surface like asphalt roads, parking lots, and sidewalks is often obscured by tree canopies, which can remarkably underestimate impervious surface area in urban areas. In order to overcome this problem, this study adopts linear spectral unmixing to detect impervious surface information through tree canopies, and further incorporates with object-based classification to mitigate the negative effects of tree canopy obscurity when extracting impervious surface from high spatial resolution imagery. The performance of the proposed impervious surface extraction method is investigated by a subset of QuickBird imagery in Beijing urban areas. Results demonstrate that the proposed method effectively reduces impervious surface underestimation in urban areas by 11.20%, and more accurate impervious surface extraction and mapping can assist government policy makers for timely monitoring of urban hydrological environment.

Interventions in Bicycle Infrastructure, Lessons from Dutch and Danish Cases

Today the interest in cycling is increasing worldwide and in many countries authorities are faced with the question how cycling can be promoted efficiently. In the Netherlands and Denmark, this question came up already in the 1970s when the downsides of the rapidly increasing motorisation became evident. At the time, in both countries large scale interventions in bicycle infrastructure were introduced and evaluated extensively in order to create knowledge on efficient promoting of cycling in urban areas. The interventions included the construction of new bicycle routes on urban arterials in some larger cities and an area wide comprehensive upgrade of the bicycle network one medium sized city (Delft). The evaluations were based on before and after studies where in the case of Delft also a long-term after study was performed. The evaluations produced a wealth of information about the impacts of interventions in bicycle infrastructure on travel choices, safety, design appreciation, and other factors. These clarify under which conditions certain measures are effective or not and inform about the effectiveness of improving a single route versus upgrading a whole network. The information from the studies was used in both countries for formulating guidelines for road and bicycle infrastructure design. However, at that time the study results were not shared with the international scientific audience. The paper describes briefly the classical cases and the main study results.The outcomes of the classical studies are compared with those of some more recent cases of assessed interventions in urban bicycle infrastructure in the Danish largest cities. Generally the outcomes are in line with those from the classical studies. This indicates that results of the latter are rather timeless and are likely to be still generally valid. In addition to studies that traditionally focus on dedicated bicycle infrastructure, two cases of shared space are discussed, a rather new type of intervention that assumes mixed use of infrastructure. One case is from Denmark, the other from the Netherlands.The paper will so uncover the valuable results of the possibly largest evaluations of interventions in bicycle infrastructure ever made, verify these by examining more recent studies, and contribute to the discussion of shared space.

분산형 빗물 저류조용 모래 여과층을 적용한 도심지 비점오염원의 TSS와 COD 정화효율에 대한 실험적 연구

도심지 불투수성 포장의 증가로 지하수위 저하, 생활용수 부족 등의 물과 관련된 다양한 환경문제가 점차 심화되고 있으며, 이를 해결하기 위해 빗물 저류조가 설치되어지고 있다. 빗물 저류조는 지반 저류층에 강우 유출수를 저장하여 향후 갈수기에 이용할 수 있어 도심지의 원활한 물순환에 도움이 된다. 그러나 도심지의 초기 강우는 다량의 비점오염물질을 포함하고 있으므로, 초기 강우를 빗물 저류조에 저류하기 전에 빗물에 포함된 오염물질을 정화하기 위한 시스템이 필요하다. 본 연구에서는 초기 강우의 오염물질 정화를 위해 경제성과 비점오염물질 제거효율 측면에서 우수한 토양여과기술을 적용한 빗물 저류조의 전처리시설인 모래 여과층에 대한 정화효율 및 적용성을 실내 시험과 현장 시험을 통해 평가하였다. 실내 시험은 <TEX>$20cm{\times}30cm{\times}60cm$</TEX>의 규격으로 제작된 챔버에 3종류의 각기 다른 모래 여과층을 조성한 후 인공 강우를 유입하는 과정으로 진행되었으며, 유출된 오염수의 TSS (총 부유물질)와 COD (화학적 산소요구량)를 측정하여 모래 여과층의 정화효율을 평가하였다. 또한 폐색 현상으로 인한 모래 여과층의 투수계수 변화를 간접적으로 평가하였다. 실내 시험을 통하여 비점오염물질 정화에 적합한 여과층을 제시하였으며, 이를 현장 빗물 저류조에 시험 시공하여 선정된 여과층의 적용성을 검증하였다. Prevalent construction of impermeable pavements in urban areas causes diverse water-related environmental issues, such as lowering ground water levels and shortage of water supply for the living. In order to resolve such problems, a rainwater reservoir can be an effective and useful solution. The rainwater reservoir facilitates the hydrologic cycle in urban areas by temporarily retaining precipitation-runoff within a shallow subsurface layer for later use in a dry season. However, in order to use the stored water of precipitation-runoff, non-point source pollutants mostly retained in initial rainfall should be removed before being stored in the reservoir. Therefore, the purification system to filter out the non-point source pollutants is essential for the rainwater reservoir. The conventional soil filtration technology is well known to be able to capture non-point source pollutants in a economical and efficient way. This study adopted a sand filter layer (SFL) as a non-point source pollutant removal system in the rainwater reservoir, and conducted a series of lab-scale chamber tests and field tests to evaluate the pollutant removal efficiency and applicability of SFL. During the laboratory chamber experiments, three types of SFL with the different grain size characteristics were compared in the chamber with a dimension of <TEX>$20cm{\times}30cm{\times}60cm$</TEX>. To evaluate performance of the reservoir systems, the concentration of the polluted water in terms of TSS (Total Suspended Solids) and COD (Chemical Oxygen Demand) were measured and compared. In addition, a reduction in hydraulic conductivity of SFL due to pollutant clogging was indirectly estimated. The optimum SFL selected through the laboratory chamber experiments was verified on the in-situ rainwater reservoir for field applicability.

Trucks and Bikes: Sharing the Roads

More cycling in urban areas could alleviate congestion that would benefit logistics operations as well as provide health and environmental benefits to the community at large. However, cycling within many Australian cities is currently being impeded due to poor road design and the absence of best practice freight vehicle standards (amongst other deterrents). Rising levels of fear and road trauma are creating the opportunity to address safety issues associated with the interaction between trucks and bicycles in urban areas. Those involved in city logistics can help to promote cycling and other forms of active transport by participating in the development and implementation of measures that increase the level of safety for cyclists. Measures that could be supported include: intersection design, design modifications for trucks, education of drivers, cyclists and road managers, enforcement aimed at behavioural change, as well as logistics customers requiring the use of safer trucks. Road management approaches with integrated safety benefits include designating routes and times for the movement of freight vehicles to avoid cyclists and requiring the trucks used in urban areas to have better visibility (e.g. lower driver position). This paper discusses several measures for improving the safety of cyclists including freight vehicle engineering and truck driver training programs as well as environmental management and land use changes.

Exploring the causal relationship between bicycle choice and trip chain pattern

Choices of bicycle and trip chain are important decisions in an individual's daily travel activities. Little is known about the causal relationship between the two decisions. It is interesting to ask if a decision on bicycle choice is made prior to the determination on a trip chain, or is dependent on the pre-determined chain pattern. This study aims to explore the relationship between the choices of bicycle and trip chain and capture the order of decision between them. Based on the survey data from a medium-sized Chinese city, the co-evolutionary approach with logit-modeling framework was estimated for the study purpose. Results show that there are more bicycle uses in the subsistence trip chains as compared to these non-subsistence ones. Considering the interaction between the two decisions improves the predicting accuracy of both bicycle choice and chain choice. In most cases, a trip chain is determined prior to a decision on bicycle choice, especially when the chain contains subsistence activities. For travelers who currently using a bicycle, most of them first decide the chain type and then choose a bicycle accordingly. Most of travelers who first determine the trip mode do not consider using a bicycle. We also estimate a model to predict the decision process of travelers. The order of decision is mainly impacted by the individual and household characteristics as well as the travel attributes. Findings of this study are discussed to assist the development of policies to promote cycling in urban areas.

城市不同地表覆盖类型对土壤呼吸的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 城市不同地表覆盖类型对土壤呼吸的影响 DOI: 10.5846/stxb201303290548 作者: 作者单位: 中国矿业大学(北京)化学与环境工程学院,中国农业大学生物学院,中国科学院生态环境研究中心城市与区域生态国家重点实验室,中国科学院生态环境研究中心城市与区域生态国家重点实验室,中国科学院生态环境研究中心城市与区域生态国家重点实验室,中国矿业大学(北京)化学与环境工程学院 作者简介: 通讯作者: 中图分类号: S731.2 基金项目: 国家自然科学基金资助项目(71273254, 30970507) Impacts of different surface covers on soil respiration in urban areas Author: Affiliation: School of Chemical and Environmental Engineering, China University of Mining and Technology,,State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences,State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences,State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences,School of Chemical and Environmental Engineering, China University of Mining and Technology 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:采用Licor-6400-09的土壤呼吸测量系统对北京市区3种不同覆盖类型地表(全硬地表、半透砖地表、草坪覆盖地表)的土壤呼吸速率及其影响因子进行了测定和分析。结果表明:(1)不同地表覆盖类型的土壤呼吸速率年均值分别为7.928 μmol·m-2·s-1(全硬地表),5.592 μmol·m-2·s-1(部分硬化地表)、2.625 μmol·m-2·s-1(草坪覆盖地表);土壤呼吸日均值最高均出现在夏季(14.785,10.296,5.143 μmol·m-2·s-1),最低为冬季(0.490,0.319,0.239 μmol·m-2·s-1);(2)3种地表类型的土壤呼吸速率有显著差异(P<0.05),大小排序为:草坪覆盖地表<部分硬化地表<全硬地表;(3)3种地表类型土壤呼吸速率均与土壤温度呈显著的指数相关,Q10值排序为:草坪覆盖地表<部分硬化地表<全硬地表;(4)土壤含水率和土壤电导率与土壤呼吸均有一定的相关性,但关系较为复杂,有待于进一步研究。 Abstract:Urban soils are one of the most important components of urban ecosystem, which provides significant ecosystem services.The surface hardening resulted from rapid urbanization and industrialization changes the material and energy exchanges between the soil and the atmosphere, changes the physical and chemical properties of soils, changes the richness and diversity of species, leads to the deterioration of urban communities environment, and affect the urban environment and ecosystem services.Soil respiration intensity, as one of the most important indicators of soil fertility, soil texture and soil permeability, is one of the key factors of the carbon cycle in terrestrial ecosystems.The supply capacity of soil nutrients is not only reflected by the level of soil respiration, but also affected by the local ecosystem primary productivity.Therefore, the study of impacts of different land covers on soil respiration rate is important for carbon cycle in urban areas.In this paper, the surface hardening is divided into full and part built-up lands, and the soft-cover land with grass is chosen as the contrast.Combining on-site sampling method with field experiments, the response mechanism of ecophysiology of soil respiration in urban areas with different surface hardening is investigated.This research aims to explore the service and stress response mechanism between soil respiration and urban environment, clarify the response mechanism and its difference under different surface hardening types, and reveal the coupling relationship and effecting mechanism between soil respiration and environmental factors.This study can provide scientific experimental parameters for improvement of ecological benefits of urban plants and optimization of urban land structure for ecosystem services, which has important theoretical and practical significance to urban ecosystems.The rapid development of urbanization makes the urban land use types changed in much degree.The original natural landscape is replaced by so many artificial buildings.Soil respiration in urban areas is one part of the terrestrial carbon flux, which is very of importance to ecosystems.Therefore, study spatial and temporal variability of soil respiration on different surface covers in urban areas and its effects on urban environment and ecosystem services is of great significance.In this article, using Licor-6400-09 soil chamber system to measure soil respiration and its main regulating factors on the three different types of urban surface covers (totally impervious cover(TIC), partially impervious cover(PIC)) and turf surface cover(TC) in Beijing, China.The results indicated that: (1) The mean annual soil respiration rate in TIC, PIC, and TC was 7.928, 5.592 and 2.625 μmol·m-2·s-1, respectively.The maximum of 14.785, 10.296, and 5.143 μmol·m-2·s-1in Summer, and the minimum of 0.490, 0.319, and 0.239 μmol·m-2·s-1 in Winter, respectively.(2) The mean soil respiration rate was significantly different among the three different land covers (P<0.05).The order of the mean soil respiration rate was: TC< PIC< TIC.(3) Soil respiration was significantly correlated to soil temperature on the three different types of urban surface covers, The order of Q10 value was: TC< PIC< TIC.(4) Soil respiration was significantly correlated to soil moisture and soil conductivity, but it is very complicated, which needs to be further studied in the future. 参考文献 相似文献 引证文献

Commuter Cyclist Travel Behavior

The study reported in this paper examined commuter cyclist travel behavior specifically in response to changes in weather. An investigation into how bicyclists made their day-to-day riding decisions provided insights into the factors that guided their behavior in adverse weather. Disaggregate travel data collected from an in-depth survey were analyzed. Examination of general commuter cyclist travel behavior led to the identification of differences on the basis of riding frequency. Weather conditions were found to be a paramount factor in a commuter's riding decisions. Further survey results were analyzed to gain insight into the influence of end-of-trip facilities and to quantify whether riders who had access to such facilities were less sensitive to changes in weather. More than half of the respondents indicated that these facilities were important, in that they encouraged the respondents to ride to work when the weather was not favorable. Given the variability in day-to-day ridership, commuter riders were expected to alternate modes when faced with adverse weather. The modal shift of commuter riders was analyzed with a logistic regression model. When the model was used to predict the probability of a shift to private transport (e.g., drive alone, get a lift from someone else, use a motorcycle or motor scooter), it correctly predicted nearly 80% of the cases. The implications of the results for government policies and strategies that seek to increase commuter cycling in urban areas are discussed.

A bikeway network design model for urban areas

This work develops a bikeway network design model for cycling in urban areas. The objectives of the proposed model are to minimize cyclist risk, maximize cyclist comfort, maximize service coverage for residents, and minimize the impact of the bikeway on existing traffic. The proposed model considers the following constraints: bikeway type, monetary budgets, path continuities, and value ranges of decision variables. Grey numbers are employed to deal with parameter uncertainties, and the proposed model is developed as a multi-objective grey 0–1 programming problem. A case study of the Xinyi District, Taipei City, is conducted. The grey one-stage algorithm is applied to solve this problem. In total, six non-dominated alternatives are generated for the case study. In comparing model alternatives with the existing network, this work confirms that the existing biking network prioritizes cyclist comfort. Scenario analyses indicate that maintaining the lower bound of the length percentage of wooded areas at 20–40 % generates better performance than that of the other scenarios, while decreasing the number of traffic accidents only decreases cyclist risk and does not alter the other objectives. The proposed model is the first network design model for bikeways in literature and will assist bikeway planners in developing alternatives for further evaluation and in developing detailed designs efficiently and systematically.

Visions for a walking and cycling focussed urban transport system

Walking and cycling can make a considerable contribution to sustainable transport goals, building healthier and more sustainable communities and contributing to traffic and pollution reduction. There have been many national and local initiatives to promote walking and cycling, but without a long term vision and consistent strategy it is difficult to see how a significant change may be achieved. This paper presents three alternative visions for the role of walking and cycling in urban areas for the year 2030: each vision illustrates a ‘desirable’ walking- and cycling-oriented transport system against a different ‘exogenous social background’. These visions have been developed through a process of expert discussion and review and are intended to provide a stimulus for debate on the potential for and desirability of such alternative futures. Each is based on the UK and represents a substantial change to the current situation: in particular, each of the visions presents a view of a society where walking and cycling are considerably more important than is currently the case and where these modes cater for a much higher proportion of urban transport needs than at present. The visions show pictures of urban environments where dependence on motor vehicles has been reduced, in two of the visions to very low levels. The methodological approach for devising visions is informed by work on ‘utopian thinking’: a key concept underlying this approach is one of viewing the future in social constructivist terms (i.e. the future is what ‘we’, as a society, make it) rather than considering the future as something that can be ‘scientifically’ predicted by the extrapolation of current trends.

A Numerical Model for the Study of Thermal Effect of Grass-Covered Parks in a Humid Urban Area

Abstract A numerical simulation is carried out to analyze the tempera-ture change of an urban green area for different times of day for a meteorologically calm condition in summer. Several parameters contribute to changes of the surface layer, e.g., irrigation, plants height, water bodies, etc. Grassland cooling effect can lead to sub-stantial decrease of energy consumption, especially in urban areas in warm seasons, for air-conditioning. In this study a numerical model for the simulation of the temperature and humidity changes of an urban grass-covered park was developed. Also the main object in this study was to determine the effect of soil and grass leaf humidity of an urban park with grass cover on air temperature in a humid city in summer. In this approach, air flow over grass was simulated using solutions of two dimensional Reynolds Aver-aged Navier-Stokes (RANS) equations and a standard k -e model for turbulence. Also heat and humidity equations with RANS equations were solved using the SIMPLE algorithm with a finite difference method. For the air surface interaction, the Deardorff Soil–Vegetation–Atmosphere Transfer (SVAT) model was used to estimate the evaporation-evaportranspiration of grass which has a key role in controlling the temperature and humidity of air over grass. For a more realistic numerical simulation, instead of well mixed air assumption for the inlet flow, a wind logarithmic profile based on stability conditions of air at the inlet of the computation-al domain was utilized. The model results, with conditions of an urban grass-covered park in Nagoya, Japan, show similar trends with observation; hence it seems that such model may be used for the study of air temperature and humidity variations, while using an irrigation program over grass, during the diurnal cycle in urban areas.