Assessment On Naturalness Degree Of Urban Woodlands In Plain Area In Beijing

Nearly natural degree evaluation for improving the quality of urban forest,the decrease of urban forest maintenance cost has important significance,this study analyzes the Beijing urban forest types,combining with the investigation on present situation of urban forest in Beijing,with principal component analysis(pca)to construct the Species composition,Stands structure,community updates,soil physical properties such as four major categories,Indexes including tree layer Shannon-Wiener index,tree layer species richness and the shrub layer Sinpson index,herbaceous species,proportion of native tree species,tree Angle scale,herb coverage,breast height per hectare area,natural regeneration seedlings number,the degree of interference,the maximum water holding capacity of soil,soil thickness almost natural degree assessment on 12 indicators,plains in Beijing city Lin carried out the study of natural degree evaluation,the evaluation results are system clustering,and rank.The main results were as follows:(1)Urban forest near nature degree evaluation from could reflect the stratified nearly natural communities,different ages,nitrogen fixation,the basic community characteristics,such as selection of plots,shrubbery,composition,species composition,diversity index,community horizontal structure,vertical structure and combining with sample to different classification method for sample analysis of plant community characteristics,provide the basis for index selection.(2)The evaluation model of naturalness and evaluation grade standard were established by principal component analysis.Beijing plain survey sample area near natural scored an average of 0.318 points,according to the result of clustering analysis from high to low was divided into four ranks,near natural high-grade(?)including 4 sample to 0.418-0.473,accounting for11.1% of the total survey sample area;Higher near-naturalness grade(?)includes 12 sample plots,and the comprehensive score of near-naturalness is 0.343-0.401,accounting for 33.3% of the total survey sample plots;Nearly natural degrees lower level(?)including eight sample area,close to natural degree comprehensive score of 0.273-0.317,accounting for 22.2% of thetotal survey sample area;Nearly natural degrees lower level(?)including 12 sample area,close to nature degree score 0.215-0.257,accounting for 33.3% of the total survey sample area.(3)According to the classification of the surveyed plots from different stand types,the comprehensive score of the near-nature of the three types of plots is as follows: public recreation forest(0.334)> water bank forest(0.318)> road shelter forest(0.295).According to the classification from the perspective of different plantation time,the comprehensive scores of four types of land proximity were as follows: before 1990(0.334)> 2000-2009(0.317)>1990-1999(0.314)> 2010 to present(0.289).According to the classification from the perspective of distribution of different loops,the results of the comprehensive score of naturalness of the five types of samples were as follows: 4-5th rings(0.322)> 5-6th rings(0.319)> 3rd-4th rings(0.318)> 2ed-3rd rings(0.315)and > 1st-2ed rings(0.311).According to the classification from the perspective of different patch areas,the comprehensive score of near-nature of the four types of land was more than 20 hectares(0.359)> 5-20 hectares(0.345)> 1-2 hectares(0.308)> 2-5 hectares(0.306).(4)Based on the comparison of stand with high natural degree and artificial pure forest,the plant allocation and spatial structure allocation mode of the community were discussed,which can be used for reference to the existing artificial forest reconstruction and the construction of near natural forest in the future.