竞争强度变化对针阔混交林红松和水曲柳径向生长的影响

Effect of competition environment changes on the radial growth of Pinus koraiensis and Fraxinus mandshurica in mixed coniferous-broad-leaved forest

以3种间伐强度处理下(15%,30%和50%)针阔混交林内优势树种红松(Pinus koraiensis)和水曲柳(Fraxinus mandshurica)为研究对象,基于3次复测数据和树轮宽度数据分析不同间伐强度处理下红松和水曲柳的竞争变化特征,探讨竞争环境变化对保留木径向生长的影响。结果表明,1)红松保留木竞争环境发生变化的单木比例随着间伐强度增加而有所下降,但竞争减弱的保留木所占比例与间伐强度正相关,重度间伐样地内竞争减弱的红松保留木所占比例最大达到63%。不同间伐强度下水曲柳保留木竞争环境发生变化的单木比例一致,竞争减弱的单木比例占50%。2)不同竞争环境的水曲柳保留木径向生长趋势基本一致,而红松保留木径向生长变化趋势有所不同。轻度和重度间伐样地内竞争减弱的红松保留木径向生长在间伐后均呈上升趋势,而中度间伐样地内竞争减弱的红松保留木和各样地竞争不变的红松保留木以及不同竞争强度下水曲柳保留木均在2013年和2014年(间伐后2年内)出现生长抑制,而在2015年(伐后第3年)得到促进。3)随着间伐强度上升,自2015年(伐后第3年)竞争减弱的红松保留木径向生长年增量明显增加,显著高于竞争不变的红松(P<0.05),而竞争减弱的水曲柳保留木径向生长年增量自2014年(伐后第2年)在重度间伐样地内增加幅度最大,其次为轻度间伐样地,而在中度间伐样地内增加幅度最低。

Pinus koraiensis and Fraxinus mandshurica as the dominant tree species in mixed coniferous-broad-leaved forest under three thinning intensities(low 15%,moderate 30%,and severe 50%)were studied in this paper.The competitive characteristics of Pinus koraiensis and Fraxinus mandshurica under different thinning intensities were quantified with three times repeated investigation and tree ring width data.The effects of varied competitive environment on radial growth were analyzed.The results showed that:1)the proportion of individual trees with change in competitive environment of Pinus koraiensis residual trees decreased with the increase of thinning intensity,but the proportion of retained trees with weakening competition was positively correlated with the thinning intensity.The largest proportion of Pinus koraiensis residual trees with weakening competition was 63%,in the heavy thinning plot.The proportion of individual trees with changed in competitive environment of Fraxinus mandshurica residual trees was the same in three plots,accounting for 50%.2)In different competitive environments,the consistent radial growth trends of Fraxinus mandshurica,but differential radial growth trends of Pinus koraiensis were observed.The radial growth tendency of Pinus koraiensis reserved trees with weakening competition in low and heavy thinning plot was raised.The radial growth of Pinus koraiensis reserved trees with weakening competition in the moderate thinning plot,Pinus koraiensis reserved trees with unchanged competition in all plots and Fraxinus mandshurica reserved trees in different competition intensities were reduced in 2013 and 2014(within 2012 after thinning),but promoted in 2015(the third year after thinning).3)With the increase of thinning intensity,the annual increment of radial growth of Pinus koraiensis reserved trees with weakening competition has been increased since 2015(the third year after thinning),which was significantly higher than that of Pinus koraiensis reserved trees with unchanged competition(P<0.05).Since from 2014(the second year after thinning),the annual increment of radial growth of Fraxinus mandshurica reserved trees with weakening competition was increased,with the largest one in the heavily thinning plot,followed by the light thinning plot.The lowest increase in annual increment of radial growth was found in moderate thinning plot.