杉木林间伐强度材种出材量和经济效果的研究

Studies on the Timber Assortment Outturn and Economic Benefit of the Intermediate Cutting Intensity for Cunninghamia lanceolata Stands

1976年6月在江西省奉新县下林场10年生杉木林中进行抚育间伐强度试验,1996年10月结束,历时20年。采用定位研究,随机区组设计,3次重复。研究揭示:不同间伐强度林分材积依照径级的分布规律呈正态分布,有一个峰值,偏向小径级位置。林分大径材材积及其比例随间伐强度增加而显著增加,小径材则相反,间伐强度之间中径材材积无显著性差异。林分活立木出材量大致占总出材量90%～95%,间伐木和枯损木约占5%～10%,间伐不能有效提高林分总出材量及伐后20年间定期增加值。强度间伐能比对照极显著增加大径材出材量,小径材则相反,中度和弱度间伐大径材出材量比对照也有显著增加,但间伐强度之间中径材出材量无显著性差异。30年生林分总产值、活立木产值及其20年间定期增加值均以强度>中度>弱度>对照;强度间伐极显著大于对照,中度和弱度间伐显著大于对照,间伐林分活立木产值及其定期增加值显著大于对照的原因系大径材产值增加的结果。伐后20年间,依照林分年平均产值及其定期年平均值的变化,从经济上分为4个时期,即上升期、高峰期、高峰延续期、下降期。研究提出以木材产品市场价值及其相应经济效果确定杉木林主伐期,可望获得较高经济效益。并以此提出不同间伐强度林分主伐期:对照24a、弱度和中度30a、强度30～35a。

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.