Study On Accessibility To Urban Green Space Based On Road Distance And Its Equity

Urban green space is an important component of urban ecosystem.It plays a crucial role in improving urban environmental quality,optimizing urban ecosystem and beautifying the city.However,the distribution of urban green space is uneven in cities due to various factors,and its accessibility is constrained by socio-demographic factors such as income,ethnicity,and age.The existing researches on urban green space mostly aim at its natural attributes,i.e.analyzing its type and area.Studies on accessibility to green space have also been carried out,but the indicators and models are very simple,and the research areas are concentrated in developed countries.Scientific measurement of the accessibility to green space and evaluation of its equity not only helps people to understand green space in depth,but also provides referencees for the rational planning and management of green space,thereby improving its quality and configuration.It can also provide theoretical and technical support for the use of green space ecological functions and service values.In this study,Beijing was selected as the modeling experiment area.Based on remote sensing extraction of vegetation information,we introduced the theory and methods of landscape ecology,proposed the representative factors to describe the landscape structure of green space,constructed a comprehensive measurement model of green space accessibility based on road distance,and analyzed its equity to socio-demographic factors in Beijing.Furtherly,we applied this accessibility measurement model to Guangzhou to verify its scientificity and effectiveness.The main results and conclusions of this study are as follows:(1)Aiming at the problem of complexity and lack of ecological significance,a set of process for screening and optimizing the landscape metrics was proposed,and the quantitative measurement of the green space landscape structure was achieved.The results showed that:?1 The landscape structure of green space can be quantitatively measured by five landscape metrics,i.e.ED,AREA_SD,SHAPE_SD,FRAC_AM and COHESION.?2 The factor analysis of above five metrics could optimize two landscape structure description factors,i.e.shape complexity and aggregation.(2)Aiming at the problem of single measure factor and simple model in existing researches,a comprehensive measurement model of accessibility to green space based on road distance was constructed,taking into account the green space quantity,landscape structure and growth status,and the scientific and effective measurement of the accessibility to green space was achieved in the study area.The results showed that:?1 The accessibile area based on road distance is more practical than the straight-line distance.The average accessible area of each grid in Beijing is 2.56 km~2.The accessible area is inversely proportional to the distance from the center of the city.?2The accessibility to green space increased from city edge to urban center first and then decreased in Beijing.The maximum appeared at 57 km from the center of the city.Tongzhou,Shunyi,Changping and Pinggu district had the highest accessibility to green space,while Dongcheng and Xicheng district had the lowest accessibility to green space.Gradient analysis in four directions showed that the accessibility curve was“V”within±35km from the center of the city.From the second loop to the six loop,the accessibility to green space increased monotonously.(3)Aiming at the limitations of single socio-demographic factor,this study explored the accessibility to green space and its equity to nine socio-demographic factors in Beijing,and found out the key influencing factors.The results showed that:The inequity of green space to socio-demographic factors varied with the changes in the measurement factors and the study area.The percentage of the population with agriculture accounts and education level were the key socio-demographic factors having significant effect on the vareity of accessibility to green space in Beijing.In general,residents with agricultural accounts had an advantage in green space accessibility over non-agricultural residents,and residents with lower education level had an advantage over residents with higher education level in green space accessibility.(4)The accessibility measurement model based on road distance was applied to Guangzhou.The research results of its accessibility and equity showed that:the accessible green space area and shape complexity in Guangzhou are significantly higher than that in Beijing.The accessible green space aggregation is similar to that in Beijing.The accessible green space NDVI is slightly smaller than that in Beijing(caused by image acquisition time).In general,the level of greening in Guangzhou is better than in Beijing.The inequity of green space to socio-demographic factors in Guangzhou is less significant than that in Beijing.Age and education level are the key socio-demographic factors having significant effect on the vareity of accessibility to green space in Guangzhou.In general,residents greater than 14 years old had an advantage in green space accessibility over residents less than 14 years old,and residents with higher education level had an advantage over residents with lower education level in green space accessibility.The accessibility measurement model of green space based on road distance showed good applicability in different research areas,and it might be a promising tool to be used widely.This study integrated the theory and methods of landscape ecology into the measurement of green space accessibility,and proposed a set of systematic technology process for green space accessibility measurement and equity research.It provided a new perspective for understanding green space in depth,added new content to the study of green space,and provided technical services for urban greening,human settlement assessment,and urban fine management.Therefore this study has important theoretical significance and practical values.