| Urban forest is the key components of urban ecosystem and structure and function is its primary characteristics. To understand the city forest structure and its relationship with function and to coordinate variety functions for the better construction is the key area. The landscape quality is the most important aspect of it's social service function.This study taking the urban forest of Beijing city as the research object, the plants composition-structure characteristics and spatial distribution characteristics are studied by the community survey as the foundation, landscape quality evaluation index and method are studied, the typical urban forest landscape aesthetic quality and the main species of monomer landscape aesthetic quality are evaluated, landscape aesthetic quality prediction test was researched. Then elaborating the structural features of the urban forest, exploring the relationship between the structure and landscape quality, revealing the main factors to affect the aesthetic quality of urban forest landscape, providing a reference for landscape construction, renovation and optimization practice of the urban forest and providing a theoretical basis for the enhancement of the urban forest ecosystem services in Beijing. The main conclusions are as follows:(1) It can be divided into72community types based on community appearance of dominant species in urban forest of Beijing city, and it can be divided into coniferous forest, broad-leaved forest, broad-leaved and coniferous mixed forest and bamboo forest four physiognomy types and seven kinds of life types. According to the urban floral category, there are633plant species in total which belong to108families and323genus in the green space in urban forest of Beijing city, which occupy63.12%,33.82%and29.62%of the total plant families, genus and species, the overall population is low and focus on Compositae, Gramineae, Leguminosae, Rosaceae, Cyperaceae such worldwide families. Pinaceae. Salicaceae and Rosaceae constituted dominant families in plant community of woody plants. Native species have a low proportion and occupy22%of the total native plant species in Beijing. Exotic species have a high proportion and occupy48.30%of exotic plants in Beijing, and native arbors, shrubs, herbs occupy62.22%,53.45%and23.56%of total species of Beijing mountainous area. It showed a certain amount of variability by influence of zonal effects and urbanization of the human disturbance. Native plants use is not enough, especially shrub and herb plants have very great application potential. A few kinds of application of high frequency application of low frequency and which was one of the reasons the vegetation landscape single.(2) Arbor, shrub, herb diversity index have certain differences in different urban forest green space from human interference. Patrick index is arranged in the herbs layer, arbor layer and shrub layer, and Pielou index is arranged in the arbor layer, shrub layer and herbs layer. Wood Simpson index, Patrick index and herb Patrick index were Gaussian model trend, herb Simpson index was exponential model trend, native wood Patrick index showed a trend of spherical model. Semivariance curve of wood Patrick index and herb (local herb) Patrick index have high Still value, woody Patrick index and Simpson index have high structural variance ratio value, native wood Patrick index are not the same trends in different directions on Sill, Nugget value and the Range process and banded anisotropic characteristics, showing a certain degree of imbalance. Wood Patrick index in the big patches distribution among have value higher or lower small patches, there is a certain difference from South to north. Herb Patrick index was lower in city center and higher in the northwestern, the rest place where the boundary complex, patch fragmentation more serious, patch is crisscross distribution. Native Patrick index regularity is obvious, the downtown area low, toward the city around extensions gradually increase. Urban forest plant species composition condition clearly influenced by the human interference, types and distribution has had a complex changes.(3) Based on the actual investigation and access relevant literature material as the basic primary evaluation factors, the indicators of the aesthetic quality of urban forest landscape were screened through grey system theory, analytic hierarchy process and statistics evaluation method. Then Identified density of canopy, coverage of herbage, stock density, diameter distribution, noticeability of dead branch, spatial relation, ornamental characteristics diversity, unified degree of shrub and grass et cl23indicators that affect the aesthetic quality of urban forest landscape of Beijing city, then evaluation index system were established.(4) Landscape sample evaluation were conducted with AHP method SM-PPC method, TOPSIS method and SBE method. Four different method for the evaluation of the landscape value does not exist significant differences, to be able to reflect the overall landscape features, credibility is stronger. Psychological paradigm's SBE method are easy operation with mass taste as evaluation standards and Evaluation results are reliable, SBE method is still effective landscape evaluation method current. The objectivity of the other three kinds of methods is strong, but the process is more complex. Four evaluation methods can be combined with practice applications. With the development of computer technology and geographic information technologies, new evaluation methods continue to emerge, has a good role in promoting the construction of urban forest landscape.(5) Landscape quality evaluation were conducted using SBE method in urban forest, and nearly nature park is the highest value and country park is the lowest value of landscape beauty in different types of urban forest, and broad-leaved and coniferous mixed forest has the highest value and deciduous broad-leaved pure forest has the lowest value of landscape beauty in different vegetation types. Different types of urban forest landscape beauty models were built using multiple quantitative method, the single factor models were constructed using curve regression method. The model fitting high, each model fitting degree is high, can reflect the characteristics of different urban forest green space and the landscape elements of landscape aesthetic quality. Crown density, herb coverage and stand density are two times curve model in test. Adjust forest structure so that the stand and canopy density are in medium level so as to form a good landscape is the key construction aspect in the future. Which provides a theoretical basis for further optimization of urban forest landscape.(6) Landscape beauty value method and gray association analysis in good agreement with the evaluation results has the very good consistency with scenic beauty estmation method and grey correlation analysis method in urban forest species monomer landscape. Monomer landscape evaluation shows that conifers landscape quality higher than broadleaf trees, exotic species higher than native species. â… ,â…¡ grade landscape tree species each accounted for18.97%and63.79%, frequency and single-number account for an absolute advantage in the urban forest. It embodies the overall appearance and style of urban forest landscape in Beijing. We should make fully exerting landscape effect to increase the application of native species. (7) Urban forest scenery aesthetic quality was predicted and tested in five different model, and chi-square statistical test shows no significant differences between the measured value and the predictive value of the five models. The BP model has high forecast accuracy, good stability, low risk, higher decision coefficient, good linear relationship and predict pass rate up to90%. Generally, the BP model prediction effect is the best, we suggest using BP model in the prediction of urban forest landscape quality.(8) POE method was used in typical parks, the results show that the current urban forest landscape construction still cannot meet the needs of users. It has a large space in increasing the quality of urban forest landscape and improving the quality of urban forest landscape constantly based on multi-disciplinary knowledge is a very hard work.
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