不同密度杉木幼林系统生产力和生态效益研究

杉木幼林系统是由４个不同密度级处理系列小区组成，栽植密度为１６６５、３３３０、４９９５和６６６０株／ｈｍ＾２（以下分别用Ａ、Ｂ、Ｃ和Ｄ代替）。这些小区土壤质地及地形别无二致，都是用１年生实生苗１９８７年春天定植。８年生时调查了这些幼林系统林木生长、冠层厚度、枝下高以及生态效益等。随着密度由Ａ增加到Ｄ：平均胸径生长量从８．１ｃｍ降到６．６ｃｍ；平均树高生长量由５．９ｍ降至５．４ｍ；平均冠层厚度自４．

STUDY ON PRODUCTIVITY AND ECOLOGIC BENEFITS OF YOUNG GROWTH CHINESE FIR PLANTATIONS SYSTEMS IN DIFFERENT DENSITIES

Chinese fir \%Cunninghamia lanceolata\%(Lamb.)Hook.]plantation systems were a series experiment plots consisted of four density treatments: 1665trees/hm\ 2, 3330trees/hm\ 2,4995trees/hm\ 2 and 6660 trees/hm\ 2 (four densities levels are taken place by A,B,C and D).There were not differences in the soil texture and topography of the experimental plots. 1-year-old Chinese fir seedlings were planted in spring of 1987. Tree growth, canopy thickness, tree height under first branch, and ecological benefit of different plantation systems were investigated at 8-year-old of Chinese fir trees. The average DBH increment decreased from 8.1?cm to 6.6?cm with the increase of plantation density from A to D, at the same time the average tree height increment decreased from 5\^9?m to 5\^4?m, the canopy thickness thined from 4.9?m to 3.3?m, the average tree height under first branch raised from 1.0?m to 2.3?m. The productivities of different density systems were 4.6, 7.3, 9.5, 10.3 t/hm\ 2\5a from A to D respectively. The systimatic runoff coefficient, liguid runoff, and solid runoff in the A density region were 1.35%, 19.4 mm/hm\ 2\5a, and 334?kg/hm\ 2\5a respectively, and those in the B density region were 0.52%, 8.1?mm/hm\ 2\5a, and 138?kg/hm\ 2\5a respectively, in the C density region were 0\^69?%, 8\^9?mm/hm\ 2\5a, 196?kg/hm\ 2\5a respectively, and 0.75%, 11.8?mm/hm\ 2\5a, 284?kg/hm\ 2\5a in the D density region respectively. The ecological benefits of B and C density region were better than others. The comprehensive evaluation results based on 5 intems including 15 category values showed that in the score of C density was 50, the score of B density was 43. The score of A density was 36, that of A density was 21.