Comprehensive Evaluation, Selection And Graduation Of The Trees For Urban Landscaping In Lanzhou

On the basis of gathering and overall investigating the relevant date of the trees for urban landscaping and exploiting on the spot in Lanzhou, applying theories of landscape dendrology, forest ecology, the culture and mangementment of landscape trees, landscape aesthetics and methods of Analytical Hierarchy Process (AHP), flora analysis, phenological observation and comprehensive evaluation, selection and graduation were made on 167 species of the trees for urban landscaping in lanzhou. The results and conclusion are summarized as follows:(1)There are 51 families, 96 genera, 167 species, 67 varieties, 14 forms, 12 cultivated varieties of the current trees for urban landscaping in Lanzhou.(2)It indicates that numerous floral elements compose in the trees in Lanzhou through flora analysis. Six families, including Rosaceae(13 genera, 33 species), Oleaceae(6 genera, 12 species), Pinaceae(5 genera, 10 species), Leguminosae(7 genera, 9 species), Cupressaceae(3 genera, 8 species), and Salicaceae(2 genera, 8 species), are considered as obviously advantage families in trees for urban landscaping and the total is 36 genera, 80 species, each accounting for 11.8%, 37.5% and 47.9% of total number of families, genera and species. Temperate genera, including Sino-genera, north temperate genera(34 genera, 82 species) have 71 genera and 133 species altogether and all kinds of them, accounting for 79.8% of total number of genera, are provided with outstanding temperate characteristics.(3)The leaf expansion period, flowering period, fruit riping period, leaf discolour period, green period and abscission period of the landscape trees in Lanzhou have been known through the phonological observation. The conclusion is that the leaf expansion period groups in the first and middle ten days of April, fruit riping period groups in August and September, abscission period groups in the first and middle ten days of October, and flowering period of the trees admiring the beauty of flowers groups in the first ten days of April and May. Green period holds 180 days or so.(4)In Lanzhou, the comprehensive evaluation system of landscape trees can be established from three hierarchies. The goal layer (OB): the comprehensive evaluation of Lanzhou landscape trees; The criteria layer(A):ecological adaptability, ecological effects and ornamental effects; The variable layer(B): including 18 evaluation factors, they are drought endurance; alkali endurance; barren endurance; cold endurance; shade endurance; water endurance; anti-wind; resistance to plant diseases; total area of leaf; green period; absorption ability of toxic gas; fungicidal effectiveness; sluggish dust ability; characteristic of flower; characteristic of leaf; characteristic of fruit; characteristic of tree's style; and characteristic of bark.(5)According to the result of the weight of comprehensive evaluation system of landscape trees by means of AHP, the weight value of ecological adaptability is the highest in criterion layer, and the result indicates that ecological adaptability is the most important part of landscape trees comprehensive evaluation system and the first choice of choosing landscape trees. Ornamental effect is less important, which will be a considerable factor of choosing and using landscape trees. The last is ecological effect, which shows that ecological effect has least influence on comprehensive evaluation system. The weight values of drought endurance, characteristic of flower, characteristic of leaf and characteristic of tree's style in variable layer are obviously higher than the others. It can be regarded that those factors have important influence on the comprehensive evaluation of landscape trees in Lanzhou. The factors of water endurance and sluggish dust ability have slight influence on the comprehensive evaluation of landscape trees in Lanzhou.(6)After having got the weight value of various evaluation from AHP, the comprehensive index of each landscape trees can be calculated in accordance with formula: Y=∑w_iY_i(w_i means the weight value of factor i; and Y_i means the results of factor i) . Then, with the distribution of various comprehensive index and practical experience, four grades of landscape trees in Lanzhou can be determined. The results show that the number of first class trees is 46, the second is 72, the third is 37, and the fourth is 9, all of them are graded according to their integral performance.The comprehensive evaluation factor system and models of landscape trees in Lanzhou district are established tentatively. It should be being perfected so that it can provide scientific basis for the planning and using landscape trees, introducing denizens and managing city forest in Lanzhou, arid land and semi-arid land.