The Analysis On Spatial Distribution And Structure Of Urban Forest In Central Beijing

Urban forest is one of the most important ecological development in the urban area of a city,which can help beautify cities,reduce dust and nosie,maintain soil quality and conserve water supply.We take the urban forests within the fifth ring in Beijing as the research object,and divided it into 4 main types including subordinated forest,road river shelter-forest,city park leisure forest,suburban recreation forest and respective subclass according to its landscape and ecological service features.Analyzed the number of patches,patch constitution,fragmentation index,Simpson's diversity index,Simpson's dominance index and aggregation index based on GF-2 high-resolutiaon images on September 16,2016 using object-oriented method.Analysed forest layer structure,the frequency of plant species,trees composition,forest structure characters in height,diameter,crown and stand densitecological,societal and economic benefits aiming at the status and problems of urban forests in Beijing.y.optimized the distribution and composition to improve urban forest functions with futher Characteristics of Beijing urban forests were described in this thesis1)In total,about 32.35%area of central Beijing are covered by urban forests with 27494 patches and total area being 22,514.79 ha.In Beijing,13.62%of all patches are large patches with area being 73.20%;however.Unbalanced and irrational distribution on different types of unban forest,subordinated forest and road river shelter-forest are the dominant landscapes,however,with high fragmented landscape and low aggregation index,the other two kinds of landscapes take small proportion.With the expansion of Beijing city,the landscape structure vaies with speicifc pattern.The fragmentation level reduces from second ring road to fifth ring road,especially highest whin 2 ring about 183.50.The accessibility of urban parks whin the third ring road is better than outside of the third ring road,especially well around the west of the second ring road but poor in south Beijing.2)Urban forests in central Beijing compose of 54 tree species in 34 genera of 27 family.The most common trees are Sophora japonica,Sabina chinensis Pinus tabulaeformis,Acer mono Maxim Populus tomentosa.The forest structures compose of double type(55.7%),multilayered type(32.9%),and single layer type(11.4%).The single layer type forest mainly distributes in the road river shelter-forest.The forest composition on genera and family are reasonable but not on species,which is all more than 10%within different rings and in different types.Sophora japonica(35.74%)is the most important species in road river shelter-forest,which is more than 3 times of other types.Trees are generally small within the fifth ring,trees with larger DBH and height are in low proportion.The density of city park leisure forest(579.91/hm2)and subordinated forest(9579.91/hm2)are more than suburban recreation forest(452.57/hm2),and road river shelter-forest(427.90/hm2).Based on these results,suggestions are promoted as follows.Strengthen space control and make full use of small patches in order to improve the quantity and quality about urban forest totally.Inrich the canopy layer of urban forest.Make full use of family trees and kind trees,besides,optimize trees composition and forest density.