密度对山毛豆幼林生长的影响

Effect of Density on the Growth of Evergreen Tephrosia candida Shrubs

  • 摘要: 在苗圃地条件下以生物固氮、抗逆性较强的热带亚热带地区优良改土和常绿灌木树种山毛豆为研究对象,开展种植密度对其幼林生长影响的试验,对植苗2年后1、2、4、8株/m2 4种初植密度的山毛豆幼林生长量进行调查与分析。结果表明:随着密度的增加,山毛豆幼林的平均胸径和平均冠幅减小,呈现出1株/m2>2株/m2>4株/m2>8株/m2的趋势;平均树高随密度变化其变化规律不明显,而幼林植株高径比则随密度增加呈上升趋势,枝下高和树高比率与初植密度呈线性相关。随林分密度的增加,山毛豆的平均单株生物量呈递减趋势,可由方程y=ax-b来描述;单株各器官生物量随林分密度增加而减少,其中干生物量所占单株生物量的比例随林分密度的增加而增大,枝、叶的生物量所占比例随林分密度的增加而减小;林分总生物量及各器官生物量均随密度的增加而增加,遵循干>根>枝>叶>皮的规律;树干生物量所占比例最大,占林分总生物量的435%~510%,而树皮生物量所占比例最小,仅占59%~65%。密度1株/m2处理的山毛豆各器官生物量及其分配比的排序为干>枝>叶>根>皮,而其余3种密度均为干>枝>根>叶>皮。

     

    Abstract: In tropics and subtropics areas, evergreen shrub species(Tephrosia candida) is good for soil improvement and afforest because of strong biological nitrogen fixation capacity and stress resistance, and then was choose as study object. The effect of density on planting growth was studied by measuring diameter at breast height (DBH), crown width, tree height and clear bole height in young Tephrosia candida stands with different densities (1 tree/m2, 2 trees/m2, 4 trees/m2 ,8 trees/m2) .The results showed that with increasing stand density, the mean DBH and the mean crown width of T. candida stands decreased in the order of 1 tree/m2 stand>2 trees/m2 stand >4 trees/m2 stand >8 trees/m2 stand. The mean tree height was not evidently influenced by the density as DBH, but the heightdiameter ratio increased with the density increment. There were positive linear correlations between clear bole height and stand density as well as between ratios of clear bole height / tree height and the stand density. The mean tree weight of T. candida decreased with increasing stand density, and their relationship could be expressed by the equation y=ax-b (y is mean dry mass, x is density, a is coefficient and b is exponent). The mean dry mass in different organs of single tree decreased with increasing density. With increasing density, the ratio of stem mass to tree mass increased, whereas that of branch mass or leaf mass to tree mass decreased. With increasing stand density, stand biomass and organ biomass increased in T. candida stands. The organ proportion was in the order of stem > roots> branches >leaves> bark in T.candida stand, and stem biomass accounted for 435%-510% of stand biomass, while bark biomass merely accounted for 590%-647% of stand biomass. The proportion in different tree organs was in the order of stem > branches >leaves > roots > bark in T. candida stand with 1 tree/m2, while it was stem> branches> roots> leaves > bark in 2 trees /m2, 4 trees/m2 and 8 trees/m2 stands.

     

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