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罗田垂枝杉不同造林密度试验研究

Experimental study on different afforestation densities of Cunninghamia lanceolata var. Luotian

  • 摘要: 探讨不同造林密度对罗田垂枝杉人工林初期生长的影响,为其定向培育的密度调控提供依据。以湖北省咸宁市6年生罗田垂枝杉人工林为研究对象,连续4年监测4种造林密度(37044444666710000株/hm2)林分的平均胸径、树高、单株材积、林分蓄积及竞争指数,采用线性混合模型进行林龄与密度的双因素重复测量方差分析,分析其生长动态。林分平均胸径与单株材积随密度增加显著减小,而林分蓄积则显著增大;密度与林龄对胸径和单株材积存在显著交互效应,即密度对个体生长的抑制作用随林龄增加逐步放大;对树高无显著交互效应(P>0.05)。造林第6年,密度3704株/hm2林分的平均胸径(8.9 cm)、树高(7.1 m)、单株材积(0.0218 m3)均达最大值,显著高于密度6667株/hm210000株/hm2林分,密度10000株/hm2林分的蓄积最大,达到107.0631 m3/hm2,且显著高于其余林分;所有林分的各生长指标连年生长量随林龄的增加先增大后降低;较小径阶林木的占比、径阶累计百分比、树高阶累计百分比及竞争指数均随密度增加而增加。造林密度对罗田垂枝杉林分及个体生长影响显著,密度效应随林龄增大而增强。罗田垂枝杉幼龄期速生性较强,应根据培育目标选择适宜造林密度:小径级速生材培育可采用10 000株/hm2高密度模式;中大径级用材培育建议采用3 704~4 444株/hm2较低密度,高密度林分需适时开展抚育间伐。

     

    Abstract: This study aimed to investigate the effects of planting density on the early growth of Cunninghamia lanceolata var. Luotian plantations, thereby providing a basis for density regulation in targeted cultivation. A 6-year-old. Cunninghamia lanceolata var. Luotian plantation in Xianning City, Hubei Province, was selected as the research subject. Growth indicators, including mean diameter at breast height (DBH), mean tree height, individual tree volume, stand volume, and competition index, were continuously monitored for four years under four planting densities (3,704, 4,444, 6,667, and 10,000 trees/hm2). A linear mixed model was employed for two-way repeated-measures ANOVA to analyze the interactive effects of stand age and density on growth dynamics. The results showed that mean DBH and individual tree volume decreased significantly with increasing density, whereas stand volume increased significantly. Significant interactive effects between density and stand age were detected for DBHand individual tree volume, indicating that the inhibitory effect of density on individual growth intensified with increasing stand age. No significant interactive effect was found for tree height (P> 0.05). At age six, the stand with the lowest density (3,704 trees/hm2) achieved the maximum values for mean DBH (8.9 cm), mean tree height (7.1 m), and individual tree volume (0.021 8 m3), which were significantly higher than those in stands with densities of 6,667 and 10,000 trees/hm2. Conversely, the stand with the highest density (10,000 trees/hm2) yielded the maximum stand volume (107.063 1 m3/hm2), which was significantly greater than that of the other stands. The current annual increment of all growth indicators initially increased and then decreased with stand age for all stands. The proportion of trees in smaller diameter classes, cumulative percentage of diameter classes and height classes, and competition index all increased with increasing planting density. Planting density significantly influences both stand-level and individual tree growth in Cunninghamia lanceolata var. Luotian plantations, and the density effect intensifies with stand age. Given its strong early-age fast-growing trait, suitable planting density should be selected based on cultivation objectives: a high-density model (10,000 trees/hm2) is recommended for small-diameter fast-growing timber production, whereas a lower density (3,704~4,444 trees/hm2) is suggested for medium- to large-diameter timber production, with timely thinning for high-density stands.

     

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