| At present,Chinese urbanization has entered to the stage of rapid development,the urbanization has become one of the important strategies in the process of national development.The land carries all the contents of human activities,and the development of society and economy is largely dependent on the growth of construction land.With the continuous development of urbanization,the excessive growth of construction land has led to the dynamic balance of urban and rural land use pattern has been broken;The phenomena of land use unreasonable layout and inefficient utilization are increasingly prominent.At the same time,the land use pattern is becoming more and more fragmented,which leads to the threat of species diversity,and the excessive growth of construction land has become a serious obstacle to the implementation of urbanization strategy.The optimization of land use pattern is of great benefit to the prosperity and stability of social economy and the improvement of ecological environment.It is an effective way for sustainable land use and biodiversity conservation.It has important theoretical value and practical significance.However,most of the current research on land use pattern optimization is based on the mathematical model.With the help of mathematical model,the future land use structure and layout are simulated,and on the basis of this,a number of optimization objectives are used to optimize the quantity and space of land use pattern.Among them,using time series extrapolation to simulate land use quantity,which leads to the increase in the total amount of construction land.The layout is simulated by the neighborhood or eight adjacent rules,the simulation is too simple to study with specific ecological processes.With the development of land in total control and reduction strategy of national construction,it needs to discuss on the problem of land use pattern optimization under the situation that the total amount of construction land does not increase urgently.It is of great theoretical value and practical significance to study this topic with the ecological process.In view of this,the Su-Xi-Chang area and the Little Egret were selected as the study case and target species,respectively.Land use pattern will be optimized from two aspects:construction land with unchanged total amount and construction land with reduced total amount.Based on the prerequisite of construction land with unchanged total amount and the Little Egret habitat network conservation,a combined approach was designed to optimize land use pattern in following four main steps:(a)identify urban-rural construction land parcels which located within 200-meter-wide migration corridors and transfer these parcels as arbor forest(moving-out parcels);(b)identify suitable areas where the moving-out parcels of the former step could be moved in(moving-in parcels),i.e.,parcels of other land use types were transferred as urban-rural construction land in same amount;(c)design three scenarios of spatial arrangement for the moving-in parcels,i.e.,the moving-in parcels were distributed to the suitable areas of the former step in first priority ranking within the same administrative unit of a)district level,or b)municipal level,and or c)the whole study area level,respectively,which correspondingly generated a)scenario one,b)scenario three,and c)scenario two;and(d)assess the results of above scenarios using landscape pattern indicators.Based on the prerequisite of construction land with reduced total amount and the Little Egret habitat network optimization,a combined approach was designed to optimize land use pattern in following three main steps:(a)in order to improve the habitat quality of the little egret,the buffer zone of the core habitat patch was set up,and the human disturbance area of the buffer was reduced;(b)In order to ensure the safety of little egret migration process,the appropriate width buffer area were set up at the two sides of the migration corridor to protect the birds,and the human disturbance area of the buffer was reduced;(c)In above two steps of reduction,there will be a reduction in the area of dry land,based on the total dynamic balance of cultivated land,it needs equal area compensation.In other words,by using the method of land ecological security zoning,the human disturbance area in the ecological core area were changed into paddy field by the rural residential land consolidation project so as to achieve the balance of arable land,that is,the second reduction in construction land.The results show that:(1)Land use pattern optimization with the situation of the total amount of construction land unchanged:(a)the optimized land use pattern of above three scenarios have reached the goals of the Little Egret habitat network conservation as well as network connectivity quality improvement.The spatial layouts of urban-rural construction land of these scenarios trend more compact,compared with that of the current land use pattern.The above scenarios have realized the aim of land use pattern optimization.(b)in scenario two,most of moving-out parcels are from Suzhou municipal city which their total size is 1019.57 ha mainly from districts of Wuzhong,Industrial Park,Xiangcheng and Changshu;while most of moving-in parcels are to Wuxi municipal city which total size is 943.61 ha mainly including districts of Chong’an,Nanchang,Beitang and Wuxi-new.The value of aggregation index of urban-rural construction land for scenario two is highest among three scenarios;while that of fragmentation index of arbor forest is lowest.In addition,the newly-added value of urban-rural construction land for scenario one is zero due to parcels’ moving-out and-in realized within the same district;while the values for scenario two and three are different due to parcels’ moving-out and-in realized among different average price districts.The newly-added value for scenario two is 2.8 times of that of scenario three.Scenario two is the optimized result finally recommended which,compared with the other two scenarios,has obtained a good balance between economic growth and biodiversity conservation.(c)the total number of patches for three scenarios,compared with that for the current land use pattern,has increased;while values of average patch area and contagion in landscape level have decreased.Values of patch density and mean shape index of urban-rural land construction land in landscape type level for three scenarios,compared with those for the current land use pattern,have increased;while values of average patch area and mean adjacency degree have decreased.The above changes show that land use patterns of three scenarios seem becoming more fragmented;however,have been optimized indeed.This conclusion also supports the previous statement that landscape pattern indicators have limitations in explaining relations between landscape pattern and ecological process.Lastly,shortcomings of the study and future research directions are discussed.(2)Land use pattern optimization with the situation of the total amount of construction land reduced:(a)the core habitat patchs of little egret were far away from human disturbance area,and the number of construction land reduction is less,but most of the core habitat patchs’ area is lower than the mean,fragmentation phenomenon is more serious.(b)the migration corridor of little egret was seriously disturbed by human beings,and the reduction number of construction and is 6542.1 hm2,accounting for more than 99%of the total area.(c)through the balance of arable land,the reduction number of urban and rural construction land in ecological core area was 213.7 hm2,and the newly added paddy field is 208.7 hm2.Finally,the total reduction area of urban and rural construction land in study area is 6755.8 hm2.Construction land with unchanged or reduced total amount combining with the specific ecological process is a new research idea and method of land use pattern optimization.It has great theoretical value and practical significance.But many realistic factors also determine that the construction of the above analysis system need constantly enrich and perfect. |
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