Evolution And Optimization Of Green Space Pattern In Central Beijing Based On Multi-source Data

The green space composed of urban green space,farmland,woodland and wetlands and waters is significant for ensuring the social harmony,economic efficiency,pleasant ecology,comfortable living and maintaining sustainable development in central Beijing.Rapid urbanization,companied with social economy development and environment disruption,has caused changed spatial patterns of green spaces.Characterizing the spatiotemporal dynamics of green spaces,figuring out its evolution mechanism and putting forward scenarios to predict the future development of green space could provide suggestions for decision-making.Four time node(1992,2000,2008 and 2016)remote sensing images from 1992 to 2016 in central Beijing were used to characterize the spatial-temporal pattern change by calculating the green space area combined with landscape metrics.We explored the influence of socioeconomic,natural and policy factors on the evolution of spatial pattern change and spatial heterogeneity to clarify the evolution mechanism of spatial pattern of green spaces using partial least squares regression and geographical weighted regression method combined with qualitative discussions.We proposed the ideal space form to solve the problems evolving in the dynamics of the green spaces,aiming at maintaining ecological safety,meeting recreation demand and protect culture.Furthermore,we could predict the area and spatial change of green spaces coupled with the systematical dynamics model and cellular automata model to simulate the development of green spaces.We also put forward various green space models to simulate scenarios and seek macro-socioeconomic strategies,spatial allocation and policy implementation proposals of green space.The research indicates that(1)For green spaces area,it has appeared "three decreases,one increases" during the study period.The area of farmland,woodland,wetland and water area decreased,grassland increased,leading to the green space loss during 24 years.The area of farmland showed a large reduction.The woodland area showed a local fluctuating point increase.Grassland area showed a small amount of stable increase.The area of wetland and water area decreased.The conversion of land use is mainly focused on the transition of farmland to construction land and woodland as well as woodland and grassland to construction land.The conversion of farmland to construction land is mainly distributed beyond the 4th Ring Rd.The conversion of woodland to construction land distributed more in the north of the central city,grassland to construction land distributed more between the 3rd Ring Rd and 4th Ring Rd.The conversion to green space distributed mainly between 4th Ring Rd and 5th Ring Rd and point spaces such as the Olympic Forest Park.(2)The landscape pattern evolution of green spaces are different.The overall landscape pattern of green space tend to be fragmented and heterogeneous.The pattern of farmland showed fragmentation and wetland and water simplification.Patches of woodland and grassland were gradually distributed.The fragmentation degree decreased and connectivity index increased.The distributional regions where the fragmentation increased happened outside the 4th Ring Rd mostly.(3)The study explored the impact of socioeconomic factors on the evolution of green spatial pattern.The results showed the social economy has a significant impact on the evolution of green space area.The spreading of construction land is the biggest factor affecting farm land layer reduced.The increasing demand of population is the core motivation of woodland increasing.The industrial structure adjustment is an important cause of the forest land and woodland increased.The total output value and the number of permanent residents have a significant impact on the fragmentation of green space.The level of urban sprawl is highly negatively correlated with green space diversity.The second industry share shows significant negative correlation with the green space connectivity.The social economy has obvious spatial difference of green space landscape.Jiuxianqiao,East Xiyuan and Qinghe edge group city zone showed the biggest influence on the landscape pattern of green space.(4)The study found that natural factors has restrictive effect on the evolution of the pattern of green space,which is relatively static.According to the spatial difference of the landscape pattern evolution in the green space,elevation obviously restricts the evolution of the green space pattern in the high altitude area of the central city.(5)Planning and government decision-making mechanism have a positive role in the formation of green space structure.The green core,the first green belt and the green belt have begun to shape.The influence of green space planning and construction on the evolution of green space pattern shows that the Olympic Forest Park has not been effectively optimized in the Olympic Park's regional landscape pattern.The construction of "three mountains and five gardens" Greenway in the western suburb has been optimized for the integrity,connectivity and diversity of the green space landscape patches in three hills and five gardens area.The implementation of the plain forest in the east of the city has slowed down the process of the loss of green space area.(6)The study regarded the ideal pattern of green space as a green space optimization pattern form to the maintenance of ecological security,recreation demand and cultural heritage protection.We used elevation and slope,vegetation coverage,water buffer,farmland,soil erosion sensitivity,geological disasters,green space accessibility,green space 500m service coverage radius of population density,use frequency of green space and the cultural heritage as 10 indicators for high,medium and low ideal optimization green space pattern.The results showed that the area of four high level of ecological security pattern accounted for 3.96%,7.51%,18.66%and 69.70%.The higher and relatively higher recreational demand area are 1307.87hm2 and 1669.76hm2,most of which are present recreational resources.The structure of cultural protection mainly considers the distribution of the cultural heritage and its buffer zone.We obtains the ideal pattern of green space by multi factor superposition.It is found that the bottom line area of green space is 1630.52hm2,the satisfactory safety pattern area is 20454.07hm2,and the ideal pattern area is 40678.02hm2,which accounts for 37.34%of the total area of the central city.Then the ideal pattern of green space is determined by the spatial connection,including ecological recreation source and connection corridor.The key ecological sources are mainly in the northwest region and the east of the central city.Key recreation sources are mainly distributed in the old city and the surrounding,and the northwest part of historic gardens.We analyzed the minimum accumulation resistance,forming 51 ecological corridors and 28 current corridors of.The study put forward 19 recreation corridors through the scenic corridor connecting recreation sources of high frequency use demand.(7)Finally,based on system dynamics and cellular automaton simulation,we simulated and green space with 3 scenario,providing social and economic macro-control strategy and space optimization strategy for the realization of the ideal pattern of green space.The results of the system dynamics model show that if the central Beijing continued to maintain the current socio-economic development,the total area of green space will continue to decrease,but it can exceed the demand of low ideal pattern.If scenario 1 is achieved,when the central Beijing has a population of 9 million 290 thousand and GDP with an average growth rate of 6.1%,the demand of medium ideal pattern can be realized.If scenario 2 is achieved,when the population of central Beijing is reduced to 8 million 590 thousand,and the average growth rate of GDP will be reduced to 4.9%,the high ideal pattern can be realized.The simulation of green space in 2035 shows that when maintaining the current socio-economic development trend,a large number of farmland is occupied by construction land.When scenario 1 simulated the medium ideal pattern of green space,that is,the middle speed of economic development and controlling population growth,the patch density,landscape shape index and edge density of green space were higher than control scenario and scenario 1.When scenario 2 simulated the high ideal pattern,that is,the slow development of economy and the further tightening of population,the most obvious change of land use was the decrease of construction land,and the increasing trend of woodland,grassland and wetland and water area.The fragmentation degree of green space decreased significantly,while the connectivity and diversity increased significantly.The green space of central Beijing was obviously optimized.We proposed to promote the construction of key ecological and recreational space and corridor through policies planning for the old city ruins parking ring,first city parking ring,second country park ring,wedge park green corridor,north south axis of ecological space and small green space.Finally,we take the practice of "leaving white and increasing green" in the central Beijing as an example to promote the practical application of this research through implementation in the guidance of the ideal pattern of green spaces.