修枝强度对水曲柳人工林生长和干形的影响

The Impact of Pruning Intensity on the Growth and Stem Form of Fraxinus mandshurica Plantations

为了探究水曲柳(Fraxinus mandshurica)幼林的适宜修枝强度,促进水曲柳生长和形成良好的干形,以15年生和20年生水曲柳人工林为研究对象,设置不修枝(对照)和对树高30%、40%、50%、60%进行修枝的5种处理,在修枝5、6 a后进行水曲柳生长和干形指标的测定。结果表明:除50%、60%修枝强度外,修枝后两林分水曲柳林木的各生长指标均高于对照,其中40%修枝强度时,两林分水曲柳林木的胸径、单株材积、林分蓄积量均最大,两林分水曲柳林木的胸径分别比对照提高了4.94%、5.56%,两林分水曲柳林木的单株材积分别比对照提高了4.38%、16.06%,两林分水曲柳林木的林分蓄积量分别比对照提高了13.59%、17.60%。修枝后两林分水曲柳林木树干的通直度、圆满度均高于对照,其中两林分水曲柳林木的树干通直度在60%修枝强度时最高,而树干圆满度均在40%修枝强度时最高,而两林分水曲柳林木的高径比在40%修枝强度时最低。结果表明,修枝后水曲柳林木生长和干形的改善主要源于水曲柳林木之间竞争的降低、光合效率的改善以及光合产物分配的变化。40%修枝强度是水曲柳林木生长和干形表现最优的修枝处理。

To explore the suitable pruning intensity for Fraxinus mandshurica young plantations that promotes its growth and results in a good stem form,this study focused on 15-year-old and 20-year-old F.mandshurica plantations.Five treatments were established:a control group with no pruning and pruning at intensities of 30%,40%,50%,and 60% of tree height.Measurements of growth and stem form indicators for F.mandshurica were taken five and six years after pruning.The results showed that,except for the 50% and 60% pruning intensities,all growth indicators for F.mandshurica in both age classes were higher than those in the control group.Specifically,at a 40% pruning intensity,the diameter at breast height(DBH),individual tree volume,and stand volume of F.mandshurica were maximized,with an increase in DBH of 4.94% and 5.56%,an increase in individual tree volume of 4.38% and 16.06%,and an increase in stand volume of 13.59% and 17.60%,respectively,compared to the control.After pruning,the straightness and roundness of the trunks of F.mandshurica were also better than those of the control group.The straightness was highest at a 60% pruning intensity,while roundness was maximized at a 40% pruning intensity.Additionally,the height-to-diameter ratio was lowest at a 40% pruning intensity.The findings indicate that the improvement in growth and stem form of F.mandshurica after pruning is primarily due to a reduction in competition among trees,improved photosynthetic efficiency,and changes in the allocation of photosynthetic products.A pruning intensity of 40% is identified as optimal for the growth and stem form performance of F.mandshurica.