| Landscape pattern optimization approach is an effective way to construct a better ecological environment and stimulate person and natural harmonious evolution.Forestry,as a scientific field with important ecological significance such as forest and wetland,has become the main body of ecological environmental protection and ecological construction,and plays an important role in the construction of ecological civilization.At present,a large of landscape pattern optimization researches have been carried out on the spatial pattern of forest and wetland,and the optimization method of landscape pattern has been formed,which takes the construction of ecological network as the main idea.The connotation of landscape pattern optimization includes quantitative structure optimization and spatial structure optimization of landscape.The combination of the two is a complete process to realize the overall optimization of landscape pattern.However,the current research of landscape pattern optimization mostly analyzes from a single content of the two,and less discusses the way of landscape pattern adjustment and optimization by combining quantity and spatial structure.The optimization process and method need to be further improved.Based on the quantitative changes and spatial characteristics of landscape patches,a complete idea of landscape pattern optimization was formed,which include landscape quantitative structure optimization,landscape conversion tendency analysis,landscape spatial structure optimization.From the ecological point of view,the purpose of this study is to promote coordinated and sustainable development.Taking the characteristics of the national economic and social development and the development status of Haikou as the base,this paper used system dynamics model to simulate the mechanism of landscape change in Haikou city,and the quantitative changes of Haikou landscape from 2010 to 2025 were analyzed under four development scenarios.According to the results of the analysis,the best scheme of landscape quantity composition is selected.Then,based on the analysis of landscape suitability and ecological benefit of forest land,according to landscape conversion tendency analysis,the landscape type conversion of patches is realized under the constraints of optimal landscape quantity composition scheme.In the end,this paper used granularity reverse method,cumulative cost distance model,spatial network analysis and hydrology analysis to constructed the ecological network of Haikou City based on the landscape pattern,which after landscape transformation.The research proposes the construction scheme of ecological sources and ecological nodes in detail,and organic combination of landscape quantitative structure optimization and spatial structure optimization is realized.The results show that:(1)The system dynamics model can simulate the complex relationships of multiple factors in the quantitative change of landscape types effectively,and the model has high simulation precision and can simulate the change trend of landscape pattern in Haikou City effectively.By simulating different development scenarios,this paper get four kinds of landscape.quantity composition schemes,including inertial development model,land planning model,ecological priority model and coordinated development model,which take the landscape pattern of Haikou City in 2025 as the prediction object.The coordinated development model can best adapt to the future development of Haikou City,and it is the best landscape quantity composition scheme.The result of coordinated development model plays a restrictive role in the analysis of landscape conversion tendency and the optimization of spatial structure of landscape pattern.The landscape quantity adjustment scheme is to turn 849.34hm2 cultivated land,6843.48 hm2 garden and 478.53 hm2 unused land to 3389.44 hm2 forestland,937.52 hm2 grassland,1027.38 hm2 water area and 2817.01 hm2 construction land.(2)Considering the main influencing factors of landscape suitability,10 evaluation indexes were selected to construct the suitability evaluation system from the four main impacts of Key aspects of suitability,include topography,soil conditions,environmental factors and human disturbance,and then paper use the suitability evaluation system evaluated the suitability evaluation of 7 kinds of forest types,grassland and construction land in Haikou.The study found that different landscape types showed three different spatial distribution trends of suitability distribution.First,Secondary broad-leaved forests,eucalyptus acacia,other plantations,shrubs and grasslands are suitable in the south but not in the north of Haikou.Second,Mangroves,Casuarina equisetifolia and coconut trees are suitable in the northeast but not in the southwest of Haikou.Third,rubber forest and construction land is suitable in the northwest but not in the southeast of Haikou.The main causes of this suitable distribution pattern are landform and human disturbance.On the whole,the suitability of different landscape types is obviously different,especially in local areas.The order of average suitability of each landscape types is that:eucalyptus acacia>rubber forest>construction land>other plantations>Casuarina equisetifolia and coconut trees>shrub>grassland>mangrove>secondary broad-leaved forest.Compared with natural forest,artificial forest has a higher suitability to the ecological environment of Haikou City,which is closely related to the special geographical location and natural environment of Haikou City.(3)From 8 aspects of water conservation,soil conservation,carbon sequestration and oxygen release and so on,25 indexes were selected to construct a perfect ecological benefit evaluation system.The ecological benefits of forestland in Haikou City are worth 3.921 billion yuan per year.Among them,carbon sequestration and oxygen release,water conservation,purification of the atmospheric environment have a higher value on the ecological balance of the region.The area of forest type has great influence on the ecological benefit,and the total ecological benefit ranking is as follows:Eucalyptus acacia(1499.98 million yuan)>secondary broadleaved forest(741.41 million yuan)>other plantations(590.45 million yuan)>Casuarina equisetifolia and coconut trees(482.00 million yuan)>mangrove(298.23 million yuan)>rubber forest(270.03 million yuan)>shrub forest(39.35 million yuan).There are obvious differences between the total value of ecological benefit of forest types and the value of ecological benefit of per hectare forest.The ecological benefits of mangrove and secondary broadleaved forest are the highest,and it highlights the differences between different forest types in the function of ecological services.(4)Based on the suitability evaluation and ecological benefit evaluation of landscape types,paper combined with the adjacent probability of patch and the spatial location of ecological source to put forward the adjacent probability index of landscape conversion,ecological source attribution index,ecological source distance index,suitability index and landscape conversion value index,and then combined them to form landscape conversion tendency index,and the organic combination of landscape quantity optimization and spatial structure optimization is realized.There is a complex relationship among the indices of landscape conversion tendency index,which reflects the main influencing factors of landscape transformation and the research achieves a good results.With the best landscape quantity scheme as the constraint,the landscape conversion tendency analysis determined the area of landscape conversion and realized the precise positioning of space.There are 3094.42hm2 patches from landscape type with low ecological benefit change to landscape type with higher ecological benefit,and this result provides good scientific guidance for the construction of ecology in Haikou City.(5)There are six landscape types were selected as the ecological landscape types of Haikou City,including secondary broad-leaved forest,mangrove forest,rubber forest,Casuarina equisetifolia and coconut trees,eucalyptus acacia and water area.The landscape composition structure with 1400m granularity is an appropriate reference for the selection of ecological sources from the perspective of global connectivity by using the granularity reverse method and principal component analysis.There are 36 ecological sources in Haikou City,and their total area is 32394.83hm2.The overall distribution trend of the ecological source is that thenorthwest is dispersed but the scale of ecological source is large,the southeast is concentrated but the scale is small,and the ecological sources are mainly separated by cultivated land and garden land.The scale of ecological sources varies greatly,it mainly caused by human disturbance,and the topography and geomorphology also have some influence on this phenomenon.The scale criteria for new ecological sources is 91.40 hm2.We need to convert 14 patches,which total 11.07hm2 to realize the Spatial connection of single ecological sources.The effect of landscape transformation tendency analysis on the enhancement of ecological sources is very obviously.The total scale of the ecological source area expanded by 1362.70hm2.(6)Considering the influence of slope,the comprehensive ecological resistance surface was constructed by using dominant and recessive ecological resistance surfaces.There are obvious differences between dominant and recessive ecological resistance surfaces,and these differences highlight the fragile parts of the ecological environment and ecological traps.The main difference areas include the red city lake and the area between urban area and Meilan airport.Different ecological resistance areas have different functions,ecological buffer zone accounts for 39.21%of total area and its main function is to protect the ecological source.Protection and utilization area accounts for 25.99%of total area and it takes protection as the main way and development is secondary,so it can manage the ecological industry properly.Key development area accounts for 18.16%of total area and it takes protection as the main way and development is secondary,so it can manage the ecological industry properly.Coordination control area accounts for 11.98%of total area and we should emphasize the implementation of ecological construction,coordinate the spatial relationship between land contradiction and landscape pattern,and control human disturbance accordingly.Restricted development zone accounts for 4.66%of total area and its development should be combined with the rational planning of regional development from the angle of ecological network,and takes ecological protection and restoration as the main direction of construction.(7)There are 81 ecological corridors in Haikou City,the total length of them is 402.46km,and the longest ecological corridor is 18.68 km.Ecological corridors connect scattered ecological sources into a whole and they are the key to the construction of ecological network.There are 33 cultivated land ecological corridors,30 garden ecological corridors,11 forestland ecological corridors and 7 construction land ecological corridors in Haikou City.Different ecological corridors have corresponding functions,and them should be classified and constructed in combination with landscape matrix.According to the length and cumulative ecological resistance of ecological corridors,them can be divided into 5 categories:71-level risk ecological corridors,31 2-level risk ecological corridors,28 3-level risk ecological corridors,14 4-level risk ecological corridors and 1 5-level risk ecological corridors.The distribution pattern of ecological corridors with higher risk grade is consistent with that of long ecological corridors,which is mainly affected by human disturbance.(8)The ecological nodes with high cumulative ecological resistance are mainly located in the middle and southeast of Haikou City,which highlight the blind area of ecological construction in Haikou City.The spatial morphology of ecological nodes is analyzed from the aspects of their functions and spatial shape characteristics,and there are 69 areas of ecological nodes were form by 76 ecological nodes.The appropriate size of ecological node was determined to be 900m by using granularity reverse method.The total area of 69 ecological node areas is 2942.05hm2,the area of maximum one is 94.75hm2,and its scale is equivalent to that of the smallest ecological source.The area of minimum one is 21.67hm2,and the difference of scale between ecological nodes is obvious.The shape and area of each ecological node are calculated by spatial network analysis.The construction of ecological nodes is accompanied by a great deal of landscape transformation,and there is 81.17%area of ecological node need to convert existing landscape types.This result highlights the importance of landscape transformation in landscape pattern optimization.According to the spatial position and environmental conditions of ecological nodes,the method of constructing wetland ecological nodes is put forward.There are 9 ecological nodes were established as wetland ecological nodes by using hydrological analysis,and their total area is 424.37hm2.According to the analysis of landscape conversion tendency and the need of ecological construction,60 ecological nodes were established as forest ecological nodes.There are 2388.00hm2 patches need to convert landscape types.(9)Based on the optimal quantity composition scheme and landscape conversion tendency analysis,this paper constructed the ecological network of Haikou City by using the method of granularity reverse method and cumulative cost distance model.The ecological network consists of 36 ecological sources,81 ecological corridors and 76 ecological nodes.The spatial distribution of these key parts of ecosystems are affected by topography and the present situation of land resource utilization,showing a general pattern that in the middle part is sparse but in the surrounding area is concentrated.It reflects the fragile part of the ecosystem in Haikou City.Through the analysis of the best landscape quantity composition,the landscape transformation tendency and the ecological network construction,this paper research on the optimization of the landscape pattern of Haikou city,which combines the quantity and the spatial structure.In 2025,the landscape pattern of Haikou City was composed of 67655.72hm2 cultivated land,38189.50hm2 garden land,44828.41hm2 woodland,6729.81hm2 grassland,19371.49hm2 water area,299.33hm2 unused land and 51834.47hm2 construction land.Follow with the final comparative analysis,the result of landscape pattern optimization is consistent with the coordinated development model of Haikou City,which effectively improves the overall connectivity of the ecosystem in the spatial structure,and it can better adapt to the development trend of Haikou City.The effect of landscape pattern optimization is good.It can provide scientific reference for the perfection of ecological construction in Haikou City andimprove landscape pattern optimization method. |
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