Landscape Pattern Dynamics And Ecological Effects Of Urbanization In Small And Medium-sized Cities Of China

As a result of human activities,urbanization is one of the important aspects of LUCC(Land Use/Cover Changes),which impact on many aspects of the ecosystem composition,structure and function,as well as regional landscape process.During the last 50 years,the fastest growing cities in China are small and medium sized cities whose population below 50 million.The dominant position of medium and small cities in the regional social development and urbanization is irreplaceable.In the past 30 years,due to amount and rapid development of small and medium cities and the rapid pace of development,the urbanization of these cities is taken more and more attention.However,the current researches of the urban landscape are more concentrated in large cities.Few researches referred to complexity and dynamic of small and medium sized cities,as well as the relationship between urban landscape pattern and urban ecosystem function.In our research,using multi-temporal remote sensing data and urban landscape pattern analysis,we explored the urban landscape pattern and ecological effect of the rapid urbanization in small and medium sized cities.The main conclusions are as follows:(1)From 1991 to 2008,Zhangjiagang city experienced a rapid urbanization development.Land use had changed dramatically.The landscape pattern of this city was more and more fragmentary.The shape of these patches was more and more irregular.There are two phase during the 18 years:main town urbanization phase(1991-2001)and rural urbanization phase(2001-2008).In the main town urbanization phase,the urban edge-expansion growth appeared in urban center areas,while in the rural urbanization phase,the urban infilling growth was obvious.In rural areas,the urban spontaneous growth type was dominant in the main town urbanization phase,while both urban spontaneous growth type and urban edge-expansion growth type coexisted in rural urbanization phase.Using Urban Expansion Phases Theory,the main town urbanization phase was characterized by diffusion,and the rural urbanization phase was characterized by coalescence.(2)Fragmentation indices(patch density,total edge,and landscape division)in land use transects of Zhangjiagang and Shanghai city had many similarities,indicating common characteristics of urbanization in different-sized city.There were,however,some striking dissimilarities between the two cities,which did not support the hypothesis that patch density increases exponentially along a landscape modification gradient.These differences may be explained by three reasons:the proportion of urban road area,the width of urban road,and land use change in suburban and rural area.The proportion of urban road area and the width of urban road,which should be considered in future research,are two main factors that have been identified to influence landscape pattern analysis.In younger and smaller cities,spatial competition between local interest groups as well as imperfect Land Managerial Systems result in the increase of fragmentation in suburb,and policymakers should pay more attention to future city planning and management.Urban fragmentation would be a key to urban landscape studies and planning as a bridge linking urbanization landscape pattern and process.(3)We analyzed landscape patterns of small and medium sized cities in the Yangtze River Delta region and the Xinjiang region from 1986 to 2000.Cities of the two regions had similar landscape pattern changes.Fragmentation and landscape diversity had been enhanced,and patches shape tended to be more regular.Landscape variability of small and medium sized cities in Yangtze River Delta tended to decrease,but increased in the Xinjiang region.Primary driving forces of urban landscape pattern change in Yangtze River Delta are population growth and mobility,but in Xinjiang is the development of agriculture.Industrial structure,transport infrastructure and policy support are three main causes of the gap between east and west China city.(4)A common Cellular Automata(CA)model incorporating macroscaled contribution factors and an innovative acquisition method of the initial state was performed in Zhangjiagang Region to simulate the local urbanization development in 2006.Using Land Use Urbanization Level(LUUL)layer and recursive threshold procedure to extract the initial state,the model was operated by the weight of summing the neighborhood effects and 4 factors in GIS.96.90%of the High Degree in the simulated result was located in the actual urban and road area.The PD of the simulated result is 0.64 per 100ha,higher than the PD of the actual urban area.And the LPI,AREA_MN and CONTAG of the simulated result were 74.25%,156.12 ha and 20.01 respectively,lower than that of the actual urban area.Results indicated that the integrated approach can rapidly and accurately simulate urbanization,and the C A-based simulated result of 2006 is more reasonable and more in accord with the Theory of Urban Convergence than the actual urban area of 2006.It demonstrated that the simulated result could provide valuable decision-support information to the local government for the urban planning policy from the urban sustainability perspective.(5)Because of the LUCC of Zhangjiagang City,it lost a lot of net primary productivity(NPP).Due to irrigation,fertilization and field management,agricultural land use area had higher productivity than the potential productivity.NPPlucc changed along urban-rural gradient in Zhangjiagang City showed a similar trend as PL AND of urban land use type.LUCC and human activities impacted on the surrounding vegetation,resulting in significant loss of NPP.Because of the correlation between urbanization process and NPPlucc,NPPlucc could be considered as a measure of urbanization level.(6)In period of 2000 to 2008,the total ecological footprint per capita and agriculture ecological footprint per capita were both increased by 28.24%and 37.67%respectively.From the 4 land types of agriculture,grassland ecological deficit occupies the largest proportion of the agriculture ecological footprint all along during the 9 years,the ecological deficit of farmland and water area take second place,and forest ecological deficit is almost zero every year.The causation of agriculture ecological deficit was industrialization and urbanization,which led agriculture land use reducing and agriculture ecological deficit badly.In order to alleviate the agriculture ecological deficit,it is necessary to take a series of measures,such as protecting cropland,making reasonable land use plan,and improving the utilization efficiency and quality of agriculture resource.(7)From 1981 to 2008,the total Biocapacity per capita dropped 16.03%,while the total ecological footprint per capita increased by 220%.Ecological deficit sharpened year after year,and the ecological security situation of Fukang City was grim increasingly.The grassland Biocapacity per capita of Fukang City declined by 52.78%,while the grassland ecological footprint per capita increased by 625%.So the grassland ecological deficit evoked a particularly glaring problem,the grassland was facing seriously eco-deficit,and it had become the most insecure factor in these areas.The causation of grassland ecological deficit was industrialization and urbanization,which led Grassland Degradation and grassland ecological deficit badly.In order to alleviate the grassland ecological deficit,it is necessary to improve the utilization efficiency and quality of grassland resource,enlarge the area of grassland,and control the population.There are three points of innovation in our study as follows:1)using urban landscape pattern analysis and gradient analysis and combining with population and economic data,we explored characteristics of the various stages of urbanization in small and medium sized cities;2)Compared urban landscape pattern and its ecological effects of small and medium sized cities between different region and different scale cities.And further revealed ecological processes and socio-economic process of small and medium cities hidden in the process of urbanization;3)Analyzed NPPlucc along the urban-rural gradient.Our research developed this new concept the Human Appropriation of Net Primary Production(HANPP),which is still needed improvement and development in its theoretical framework.In short,through the analysis of landscape patterns and its ecological effects,we concluded that small and medium sized cities had experienced a period of rapid urbanization during the last 30 years,and land use dramatically changed.Urbanization of small and medium sized cities developed from main town urbanization phase(1991-2001)to rural urbanization phase(2001-2008).Small and medium sized cities will remain the trend of rapid urbanization in next 10 years.Urbanization had resulted in significant loss of net primary productivity,ecological carrying capacity decline,and the regional ecological deficit worse.Therefore,we must take effective measures,such as rational planning and scientific management,in order to improve the sustainability of small and medium sized cities.