间伐对不同龄组华北落叶松人工林直径生长的影响

Effects of thinning on diameter growth of Larix principis-rupprechtii plantations of different age groups

间伐是最有效、最常用的森林调控措施,研究间伐对直径生长的影响及直径分布动态,可为科学制定经营措施及森林精准经营提供技术依据。本研究以塞罕坝华北落叶松人工纯林(幼龄林、中龄林、近熟林)为研究对象,每种龄组设置间伐和对照样地各3块,共18块,基于2014-2018年直径数据,采用单因素方差分析和三参数Weibull分布,探究间伐后不同龄组林分直径生长规律。结果表明:(1)间伐促进了不同龄组华北落叶松的直径生长,间伐样地后2年直径生长量明显大于前2年(P<0.05),对照样地则差异不显著(P>0.05);间伐对林分直径生长量的促进作用表现为:中龄林>幼龄林>近熟林。(2)不同龄组间伐和对照样地的直径分布均符合三参数Weibull分布,且中龄林的拟合效果最好;2014-2018年,间伐样地的拟合参数c趋近于3.6,直径分布趋于对称分布,对照样地则变化不大。(3)间伐样地后2年林分直径分布曲线较前2年向右移动距离大,幼龄林的直径分布由右偏趋于对称,中龄林、近熟林则由左偏趋于对称。总之,间伐可有效促进华北落叶松幼龄林、中龄林、近熟林的直径生长,对中龄林的生长促进作用最强。

Thinning was the most effective and common forest regulation measure.Studying the effect of thinning on diameter growth and diameter distribution dynamics could provide technical basis for scientific management measures and accurate forest management.In the study,the pure plantations of Larix principis-rupprechti(young forests,middle-aged forests,near-maturity forests)were selected as the research objects in Saihanba,3 plots of thinning and 3 plots of control plots were set for each age group,with a total of 18 plots,based on the diameter data from the year of 2014 to 2018,single factor analysis of variance and three-parameter Weibull distribution were used to explore the diameter growth regular of different age groups after thinning.The results showed that:(1)Thinning promoted the diameter growth of L.principis-rupprechtii at different age groups,and the diameter growth increment in the second 2 years was significantly greater than that in the first 2 years(P<0.05),but there was no significant difference in the control plots(P>0.05).The promotion effect of thinning on stand diameter growth increment was as followed:middle-aged forests>young forests>near-maturity forests.(2)The diameter distribution of thinning and control plots of different age groups conforms to the three-parameter Weibull distribution,and the fitting effect of middle-aged forests was the best.From the years of 2014 to 2018,the fitting parameter c of thinning sample plots tended to be 3.6,and the diameter distribution tended to be symmetrical,but there was little change for normal plots.(3)The diameter distribution curve of the second 2 years of thinning plot moved more to the right than that of the first 2 years,the diameter distribution of young stands tended to be symmetrical from the right,while that of the middle-aged forests and near-maturity forests tended to be symmetrical from the left.In conclusion,thinning could effectively promote the diameter growth of young forests,middle-aged forests,near-maturity forests of L.principis-rupprechtii,and the growth of middle-aged forests was the strongest.