抚育间伐后蒙古栎阔叶混交林径级结构及生长动态研究

Study on Diameter Structure and Growth Dynamics of Mixed Quercus mongolica Broad-leaved Natural Stands After Tending Thinning

    摘要
  • 摘要: 以30年生的蒙古栎阔叶混交林为研究对象，设置强度间伐（41%）、中度间伐（30%）、弱度间伐（12%）和对照4种处理，利用伐后23 a的长期连续观测数据，比较分析了不同间伐强度对林分生长及径级结构的影响。结果表明：中、弱度间伐在一定程度上能够促进林分胸径和蓄积量的生长，间伐23 a后，中、弱度间伐样地平均胸径分别比对照增加了1 cm和1.7 cm，蓄积量分别比对照增加了8.5%和16.9%。在间伐后0～9 a，间伐样地的蓄积年生长率显著高于对照；而伐后11～23 a，间伐样地的蓄积年生长率低于对照。林分枯死率表现为在伐后0～11 a，强度间伐样地平均枯死率为对照的19.83%，中度、弱度间伐样地的平均枯死率分别为对照的23.93%、67.87%；在伐后的11～23 a，间伐样地的平均枯死率略高于对照。间伐使Weibull分布曲线向右移动，右移幅度随间伐强度增加而增加，且位置参数a受间伐和林龄影响较大，因此，在采用Weibull参数对林分径级结构进行拟合时，不宜将参数a设成定值。总之，中度、弱度间伐能够促进林分胸径和蓄积量的生长，减少林木枯死率，但这种促进作用并不是一直持续的，在伐后的10 a左右，促进作用逐渐减弱，因此，为提高林分生产力，建议抚育间隔期确定为10 a左右。本研究可为科学合理的确定间伐强度、间伐周期提供参考。

     

    Abstract: We established 3 different thinning regimes (light, 12%; medium, 30%; heavy, 41%) and a no-thinning(control) treatment in 30 years old mixed Quercus mongolica broad-leaved natural stands. The effects of thinning on dynamic changes of diameter structure and stand growth were analyzed based on stand inventory for 23 years after thinning. The results showed that medium thinning and light thinning could promote the increase of stand diameter and volume. Compared with the control, the DBH of medium and light thinning plots increased by 1 cm and 1.7 cm, respectively, and the volume increased by 8.5% and 16.9%, respectively, after thinning for 23 years. The annual growth rate of volume of the thinning plots was significantly higher than that of the control in the first 9 years after thinning, while, it was lower or similar to that of the control during the 11th to the 23rd years after thinning.The mean death rate of the intensively thinning plots was 19.83% of that of the control in the first 11 years after thinning, and the mean death rate of the medium and light thinning plots were 23.93% and 67.87% of that of the control, respectively. While in the 11−23 years after thinning, the mean death rates of the thinning plots were slightly higher than that of the control. Thinning shifted the Weibull distribution curve rightwards, and the movement amount increased with thinning intensity. Location parameter 'a' was greatly affected by thinning and forest age. Therefore, location parameter 'a' could not be set as a fixed value when Weibull parameter was used to fit the stand diameter structure. In a word, medium and light thinning could promote the growth of stand DBH and volume, reduce the death rate of trees, but this effect was not always sustained, and the effect gradually decreases about 10 years after cutting. Therefore, in order to improve the stand productivity, it was suggested to set the planting thinning interval as about 10 years. This study can provide references for scientific and reasonable determination of thinning intensity and thinning cycle.

     

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