Abstract:

Chinese fir [Cunninghamia lanceolata(Lamb.)Hook.]plantation systems were a series experiment plots consisted of four density treatments: 1665trees/hm², 3330trees/hm²,4995trees/hm² and 6660 trees/hm² (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 8.1cm to 6.6cm with the increase of plantation density from A to D, at the same time the average tree height increment decreased from 5.9m to 5.4m, the canopy thickness thined from 4.9m to 3.3m, the average tree height under first branch raised from 1.0m to 2.3m. The productivities of different density systems were 4.6, 7.3, 9.5, 10.3t/hm²·a 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/hm²·a, and 334kg/hm²·a respectively, and those in the B density region were 0.52%, 8.1mm/hm²·a, and 138kg/hm²·a respectively, in the C density region were 0.69%, 8.9mm/hm²·a, 196kg/hm²·a respectively, and 0.75%, 11.8mm/hm²·a, 284kg/hm²·a 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.

Key words: Density level, Ecologic benefit, Liquid runoff, Solid runoff, Economic benefit, Productivity