| As one of the central cities in Northeast China,Harbin is in the stage of rapid urban expansion and development.A lot of ecological land with important ecological functions in Harbin has been converted into construction land,which has resulted in a series of environmental issues,and the ecosystem services couldn’t meet the needs of citizens.Therefore,the quantity and spatial pattern of ecological land affect the stability and safety of urban ecosystems.The studies about the spatiotemporal change and simulation of ecological land pattern have gradually become one of the important hot spots.At present,most of the researches on the spatiotemporal change of ecological land pattern focused on the analysis of the law of historical change,and only paid attention to the quantitative change of ecological land.There are few studies have analyzed the spatiotemporal change of ecological land from the perspective of ecological land quality and ecological function.In the study of the simulation of urban ecological land pattern,there are few studies have considered the spatial relationship between the ecological functional attributes and the ecological land pattern.In addition,most of the simulation models applied in the study of ecological land pattern haven’t considered the influence of the interaction between driving factors,and they have ignored the impact of the relationship between natural ecosystems and socio-economic systems on the quantity of ecological land.These problems have led to that it is impossible to simulate the demand quantity and spatial pattern of future urban ecological land scientifically and reasonably.In order to solve these problems,this study analyzes the quality change of ecological land from the perspective of the spatiotemporal change of ecological service value,for revealing the evolution law and mechanism of ecological land pattern in Harbin more comprehensively.In order to link the ecological function attribute with ecological land pattern together,this paper uses the Minimum Cumulative Resistance Model(MCR)model to divide the ecological protection zone in Harbin,which is set to the module of spatial policies and restrictions in the CLUE-S model.In addition,this study explains the effects of interactions of various factors in the evolution process of ecological land based on the SD model,and simulates the ecological land pattern in Harbin under multi-target scenarios in the future based on the CLUE-S model coupled with the SD model.The results are as follows:(1)From 2000 to 2015,the area of ecological land in Harbin has decreased by 665.2 km~2,and the reduction rate was increasing faster and faster.The area of cultivated land,grassland and wetland has decreased,while the area of water and forest land has increased by 374.72 km~2and 194.40 km~2 respectively.The area of bare land and construction land increased year by year,and the expansion speed was also accelerating.This shows that Harbin is in the stage of rapid urban expansion and development.The expansion of construction land occupies a lot of ecological land such as cultivated land,grassland and wetland.The grassland and bare land on the edge of the city changed into construction land.The woodland,which is far from the city or near the road or village land,has been transformed into cultivated land.Most of the bare land and wetland has been converted into cultivated land.It shows that the transformation of ecological land and non-ecological land is closely related to the food needs of residents,the distance to residential area,and the distance to traffic lines.In addition to the influence of natural factors and the influence of economic and social factors,the spatiotemporal change of ecological land pattern was influenced by the natural factors,economic and social factors.Therefore,this study selects 16 representative driving factors to build the driving force indicator system from three aspects:natural factors,economic factors and social factors.(2)From 2000 to 2015,the total of ecosystem service value(ESV)in Harbin fluctuated over the years,but the total change trend of the ESV was reducing.The areas with higher ESV values are mainly concentrated in the water area,wetland and woodland in the southeast of Harbin.The gravity center of ESV is mainly concentrated in areas with high ESV values.It is obvious that the ecological quality of the upstream of Songhua River was getting better,according to the spatial change of the gravity center of ESV.In general,the spatiotemporal change of the ESV in Harbin is relative to the spatiotemporal change of ecological land pattern.The regulation services and support services of ecological land account for a large proportion,while the ecosystem services of the hydrological regulation,biodiversity conservation and soil conservation are more important.The important ecological“source”area in Harbin is recognized based on the above characteristics of the ESV change,then determining the resistance coefficient of ecological land expansion,finally dividing the ecological protection zone by the MCR model.The areas with lower cumulative resistance values in Harbin are mainly distributed in the water area,wetland,woodland and the cultivated land far away from the city,where the landscape connectivity is relatively better.The ecological protection zone can be recognized as the area with the lower cumulative resistance values,which is prepared for the simulation of ecological land pattern.(3)This study simulates the demand quantity of ecological land by the SD model,and the ecological land change system dynamics model includes the social subsystem,the economic subsystem,the land subsystem.The relative error of the results is less than 0.95,which illustrates that the demand of ecological land in Harbin can be well simulated.In addition,based on the ecological land in 2000,this study carried out the logistic regression analysis based on the previously selected driving factors.The 200m×200m grid resolution with the highest ROC value was determined as the research scale.And then,the results of the ecological land demand and ecological protection zone were input into the CLUE-S model for simulation.The Kappa index was 0.89898,indicating that the selected driving factors and ecological protection zone can better explain the spatial variation of ecological land pattern in Harbin.This paper simulates the ecological land pattern in Harbin in 2030 under four target scenarios by coupling the SD model and the MCR model into the CLUE-S model.Not only the interaction between various factors in the evolution process of ecological land is considered,but the ecological function attribute could be closely linked to the ecological pattern to determine the quantity and layout of the ecological land.(4)Through the analysis of the ecological land pattern of Harbin in 2030 under the four target scenarios,it demonstrates that the spatiotemporal change of ecological land pattern is closely relative to the urban development speed.There are many conflicts between the protection of ecological land and the expansion of urban land.Under the dominant scenario of economic construction,wetland,grassland and other land with important ecological service functions are occupied by construction land and cultivated land.In the future,it is necessary to prohibit the development and construction in areas with weak ecological sensitivity,and to divide the basic ecological red line and ecological protection area.Under the dominant scenario of ecological construction,the protection of ecological environment is generally better,but there are relatively serious phenomena of water and soil erosion.It is necessary to strengthen the vegetation protection around the waters and the watershed ecological restoration,and promotes the implementation of conservation tillage.Under the economic-ecological balance scenario,ecological land protection and urban land expansion are in a relatively balanced state.Because of the expense of cultivated land to meet the needs of urban expansion,there is a certain threat to food security.It is necessary to solve the conflict between cultivated land and construction land by the fallow rotation in the future.Under the slow economic-ecological development scenario,the water area has been greatly reduced,and there are phenomena of land reclamation.It is necessary to strengthen urban river comprehensive management,ecological restoration,and returning farmland to lakes to restore the important watershed ecosystems.The results of ecosystem service value in different scenarios indicate that the faster the urban development speed,the less the ecosystem service value.There are the higher ecosystem service value in the southern mountain forests,where should be divided as an ecological protection zone in the future,in order to protect the integrity of the ecosystem.By proposing corresponding planning suggestions for the ecological land pattern of Harbin in the four scenarios,it can achieve the purposes of the reasonable control of land use,protecting important ecological systems,maintaining urban ecological security,and the balance between the urban economic development and ecological environmental protection. |
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