| As one of the most important physical characteristics of landscape forest appearance,vegetation color is the first information received by human vision and affecting the perception of landscape.As their high value in landscape aesthetics,it is urgent to quantify the color characteristics and optimize the color patterns of landscape forests.The capacity of landscape quality would promate the tourism potential of an area by affecting the experience of tourists.Evaluation of the landscape aesthetic quality for the area is the basis of its landscape structure adjustment and important to improve the economic benefits of forest resources on the basis of forest ecological functions.Four typical plant communities were selected in Lixian County,Sichuan Province,including broad-leaved mixed forest(BMF),coniferous and broad-leaved mixed forest(CBMF),coniferous-leaved pure forest(CPF)and broadleaved pure forest(BPF).From September to November of 2018 and in early May of 2019,to obtain landscape photos we tracked and photographed around 50 meters above the center of each plot using UAV every 5 to 10 days.Based on the HSV color mode,the color information(hue,saturation,lightness)of the images were quantified by MATLAB program writing by myself,and the patches were classified using ArcGIS and FRAGSTATS software,and the spatial patterns of color patches were calculated.Using BIB-LCJ evaluation method,the questionnaires were designed and distributed to obtain the scenic beauty estimation values of autumn landscape photos,the questionnaire evaluation groups came from different types of people(profession,age,gender,education background,residence).At the same time,the species composition and structure of tree layer in the selected typical communities were investigated.In this paper,we studied spatial variabilities of color attribute of subalpine landscape forests,evaluated the aesthetic quality of subalpine landscape forests in autumn and found out how the landscape elements affect the aesthetic quality of landscape from the perspective of community characteristics and color characteristics in western Sichuan.The main results are listed as follows:(1)The seasonal change of the color of the appearance of subalpine landscape forest in western Sichuan is obvious,and the color saturation and lightness are concentrated in the middle level in spring to autumn.During non-color period from spring to summer,color coverage of landscape is narrow and mainly green.During the color period in autumn,landscape color covers a wide range of hue,mainly red,orange,yellow and green,the order of which is percentage of green(H3)> percentage of orange(H1)> percentage of yellow(H2)> percentage of red(H0).Because red,orange and yellow constitutes a contrast color with green,the color of landscape in autumn creates a strong visual effect.The pleochroic period starts early October and ends in early November,the color characteristic indexes of landscape forests in subalpine region of western Sichuan has changed significantly,color index(C),percentage of red(H0),percentage of orange(H1),percentage of yellow(H2),number of colors(NC),number of patches(NP),landscape shape index(LSI),division index(DIVISION),patch diversity index(SHDI)and patch evenness index(SIEI)all show a trend of increases at first and then decreases with passage of time,reaching their maximum in middle October.Over time,Contagion index(CONTAG),largest patch index(LPI)and aggregation index(AI)all show a trend of decreases at first and then increases,decreasing their minimum in middle October.The color index in late October is significantly lower than that in mid-October,but still has a large color index.The results based on variance analysis of the differences of color characteristics between pure and mixed stands at the same period showed that: S0 and S3 had significant differences between pure and mixed stands at the initial stage of discoloration;NC,H0,S2,LPI,CONTAG,DIVISION,SHDI and SIEI had significant differences between pure and mix stands at the peak stage of discoloration;LPI,CONTAG,DIVISION,SHDI and SIEI are different between pure and mixed stands at the end of discoloration.(2)Different types of people have their own characteristics in landscape aesthetics.People with similar professional backgrounds have more consistent aesthetic evaluation criteria.The beauty curve of the expert group is steep compared with the other three groups,indicating that the stronger the discrimination ability of the expert group,and the more stringent the aesthetic standards.The aesthetic discrimination ability between women and men,between young people and middle-aged and old people is equivalent,indicating that the aesthetic evaluation criteria are relatively consistent.People with similar educational background have more consistent aesthetic standards,and people with higher educational background have more stringent aesthetic standards and stronger ability to distinguish "good" and "bad" landscapes.People who live in cities have better aesthetic discrimination than those who live in the countryside.The Scenic beauty of each landscape is expressed by the average evaluation value(T)of different groups,and it is divided into five grades(I-V)according to the arithmetical method.The results show that about 76 % autumn landscape forests in subalpine region of western Sichuan can be classified into grade I,II,and III.This suggests that the autumn landscape forests in western Sichuan have high ornamental value and economic benefits.According to the estimation of scenic beauty,the order is broad-leaved mixed forest > coniferous and broad-leaved mixed forest > coniferous pure forest > broad-leaved pure forest > shrub forest.(3)Among color elements,C,NC,H0,H1,H2,V2,V3,S2,and S3 have a significantly positive correlation with scenic beauty estimation values,and H3,H10,S0,S1,V0 and V1 have a significantly negative correlation with scenic beauty estimation values.NP,E',H',SHDI,LSI,SIEI,DIVISION of color space pattern indexes have a significantly positive correlation with scenic beauty estimation values,and AI,CONTAG,LPI have a significantly negative correlation with scenic beauty estimation values.The autumn landscape forests in subalpine region of western Sichuan could be classified into three types based on cluster analysis.Landscape forests with higher ornamental value have larger degree of patch fragmentation and heterogeneity,higher largest patch index,lower contagion index and aggregation index,higher percentage of red,orange,and yellow,lower percentage of green,higher color saturation and brightness and,higher color diversity and evenness index.Abundance of evergreen species ratio of community characteristics indexes have significantly negative correlations with scenic beauty estimation values,and abundance of dominant species ratio,abundance of colorfulleaf species ratio,species richness,species diversity index,species evenness index,colorful species richness,colorful-leaf species diversity index,colorful-leaf species evenness index have a significantly positive correlation with scenic beauty estimation values.The results of stepwise regression analysis indicate that abundance of colorful-leaf species ratio and colorful-leaf species diversity index have the strongest influence on scenic beauty estimation values.To conclude,the seasonal changes of the color of the subalpine landscape forests in western Sichuan are obvious.The best viewing period of autumn landscape forests are in the middle of October and lasted about 20 days,autumn landscape forests in subalpine region of western Sichuan presents colorful scene over this period.Although different types of people have their own characteristics in landscape aesthetics,they have generally consistent aesthetic values,all of them agree that the autumn landscape forest in western Sichuan has a higher aesthetic quality.In the construction of autumn landscape forest,the species and quantity of color-leaf species should be increased,and the diversity and fragmentation of color should be paid attention to.The aesthetic quality of autumn landscape forest should be improved by planting and cultivating species with diverse leaf color and bright color.The results of this study provide an important scientific guidance for the cultivation and management of subalpine landscape forest in western Sichuan. |
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