Abstract:

The intermediate cutting intensity experiment was conducted in the Cunninghamia lanceolata stands at the age of ten on Zaoxia Forest Farm of Fengxin County, Jiangxi Province in June, 1976 and was finished in October, 1996. It lasted twenty years. The position research and randomized block design with three replicates were adopted. The studies indicated that the volume of the stands with different intermediate cutting intensities was in the normal distribution according to the distributive law of diameter classes and there was peak value close to the small-diameter class position. The volume of the stand large timber and its proportion increased evidently with the increase of the intermediate cutting intensity, but the small wood situation was contrary. The middle wood volume is not obviously different among the intermediate cutting intensities. The standing timber outturn accounts for 90%～95% of the total stand outturn and 5%～10% for the intermediate cutting trees and the withered and damaged trees. The intermediate cutting can't effectively enhance the total stand outturn and the periodic increment during the twenty years after the cutting. The strong intermediate cutting extremely and evidently increased the large timber outturn as compared with the control, but the small wood was on the contrary. The large timber outturn of the moderate and weak intermediate cutting also increased evidently as compared with that of the control, but the middle wood outturn is not significantly different among the intermediate cutting intensities. The total output value and standing timber output value of 30-year-old stands and their periodic increment during the twenty years from different intermediate cutting intensities were those from the strong>those from the moderate>those from the weak>those from the control. Those from the strong were extremely and evidently larger than those from the control, and those from the moderate and weak were evidently larger than those from the control. That the standing timber output value (and its periodic increment) of the intermediate cutting stands was evidently larger than that of the control was the result of the large timber output value increase. The twenty years after the cutting were divided into four periods according to the change of the annual mean output value and its periodic annual mean value of the stands, I.e.the ascendant period, the peak period, the peak continuation period and the descendant period. The studies proposed that the higher economic benefit can be obtained by determining the final cutting time of C.lanceolata forests according to the timber product market value and its corresponding economic benefit. The final cutting time for the stands with the different intermediate cutting intensities: 24 years for the control, 30 years for the weak or moderate intermediate cutting and 30～35 years for the strong intermediate cutting.

Key words: Cunninghamia lanceolata forest, intermediate cutting intensity, timber assortment structure, timber assortment outturn, economic benefit