六盘山南坡不同密度华北落叶松人工林年内径向生长动态及其影响因素

Intra-annual Radial Growth Dynamics of Larix principis-rupprechtii Plantations with Different Stand Densities and Its Response to Environmental Factors

[目的]探究不同密度下华北落叶松人工林林分径向生长的季节变化特征及其对环境因子的响应,为准确评估和预测未来区域尺度上华北落叶松人工林树木径向生长和森林动态、实现可持续管理与多功能维持提供科学依据。[方法]在宁夏六盘山南部香水河小流域,设置4种不同密度华北落叶松样地,使用树木生长尺对华北落叶松年内径向生长过程进行监测,并同步监测气象因子、土壤温度和湿度。[结果]表明:(1)在生长季时间尺度,华北落叶松径向变化呈“S”型,径向变化呈相对稳定、快速增大、涨缩波动3个阶段的时间格局,快速增大阶段主要发生在6月初—7月下旬,DOY152—210。(2)在544、742、999和1020株·hm^(-2)的密度下,生长季节内华北落叶松林平均累积径向生长量分别为1070±230μm、775±181μm、518±214μm和494±124μm;随林分密度的增加,华北落叶松年内累积径向生长量呈下降趋势,其快速增大阶段缩短;(3)混合效应模型分析结果表明,华北落叶松径向生长主要受土壤水分和平均气温控制,但林分密度和生长时期对年内径向生长也有显著影响;同时考虑林分密度、生长时期、树木大小以及气象因子等变量的模型可解释72.0%的方差,但排除林分密度和生长时期因素后,树木大小和气象因子共同仅能解释46.4%的方差。[结论]超过2/3的华北落叶松径向生长发生在快速生长期;华北落叶松平均累积径向生长量随密度增大而减小;林分密度、生长时期、树木大小和气象因子共同调控树木的年内径向生长。

[Objective]To investigate the seasonal variation characteristics of radial growth of Larix principis-rupprechtii plantations with different densities and its responses to environmental factors for providing a scientific basis for accurate assessment and prediction of the radial growth of L.principis-rupprechtii at regional scales,and achieving sustainable management and multi-functional maintenance.[Method]In the small watershed of Xiangshui River in the south of Liupanshan,four sample plots of L.principis-rupprechtii with different densities were set up,and the intra-annual radial growth process of L.principis-rupprechtii was monitored using a manual band dendrometer,and meteorological factors,soil temperature and humidity were monitored simultaneously.[Result]The results indicated that:(1)in the growing season,the radial growth of L.principis-rupprechtii showed a"S"curve.The rapid increasing stage mainly occurred from early June to late June,DOY152‒210.(2)The average cumulative radial growth of L.principis-rupprechtii decreased with the increase of stand density.In the plantations with densities of 544,742,999 and 1020 N·hm^(-2),the average cumulative radial growth of L.principis-rupprechtii was 1070±230,775±181,518±214 and 494±124μm,respectively.With the increase of stand density,the cumulative radial growth of L.principis-rupprechtii showed a downward trend during the year,but its rapid increasing stage was shortened.(3)The results of mixed-effect model showed that the radial growth of L.principis-rupprechtii was mainly affected by soil moisture and average temperature,but stand density and growth period also had significant effects on radial growth during the year.The model including the variables of stand density,growth period,tree size and meteorological factors could explain 72.0% of the variance,but after excluding the factors of stand density and growth period,model with tree size and meteorological factors could only explain 46.4% of the variance.[Conclusion]More than two-thirds of the radial growth of L.principisrupprechtii occurrs the rapid growth period.The average cumulative radial growth of L.principis-rupprechtii decreases with increasing density.Stand density,growth stage,tree size and meteorological factors jointly regulate the intra-annual radial growth of trees.