不同林龄胡杨克隆繁殖根系分布特征及其构型

以中龄林和成熟林胡杨为研究对象,采用挖剖面和根窗的方法,研究胡杨繁殖根系分布、根系构型,以及胡杨根蘖与繁殖根系构型之间的关系。结果表明:(1)细根(d<2 mm)的根长密度、根表面积密度,随深度增加呈现指数函数分布;(2)中龄林细根的根长密度、根表面积密度在0-90 cm各层都是显著大于成熟林的对应指标(P<0.05),成熟林的中等粗根(5 mm<d<20 mm)、粗根(20 mm<d)根长密度及根表面积在深层(70-90 cm)和中浅层(40-50 cm)都显著大于中龄林的对应指标(P<0.05);(3)在中龄林中,根表面积、根分枝数、根分形维数及平均分枝角度是分析根系构型的主成分因子,而在成熟林中,根体积、根分枝数及平均分枝角度是分析根系构型的主成分因子;根系各径级的主成分分析显示1-2 mm各个径级对根系表面积和根体积影响显著;(4)两种林龄繁殖根系上的不定芽及分蘖株数均无显著差异(P>0.05),且两种林龄的一级侧根数、分枝角度亦无显著差异(P>0.05);(5)对比两种林龄不同根序上的根蘖芽发现,二级根上不定芽个数均是同组一级根上不定芽个数的3-4倍;基于以上对胡杨根系的功能权衡的分析,得出:细根对胡杨根系构型有重要的影响,在胡杨根系功能权衡中扮演重要角色。

Cloning root system distribution and architecture of different forest age Populus euphratica in Ejina Oasis

Plant population regeneration is of great importance for restoration of degraded ecosystems and preservation of biodiversity in the extreme arid region. The effects of soil environment on the characters and sprouting of propagative root of populus euphratica were investigated to elucidate the development mechanism of adventitious buds and root suckers. It was contributive to ameliorate the regeneration of the degraded riparian forest in the Northwest of China. Based on the investigation on soil profile and rhizotron in middle-aged and mature-aged Populus euphratica forest, the cloning root distribution characteristics, the root architecture, and the relationship between the sucker root and propagative root architecture were analyzed. Results show that: (1) with the increasing of the soil depth, the root length density (RLD) and root surface Area density (SAD) of fine root (d<2 mm) present the exponential function. (2) In different depths among 0-90 cm, the RLD and SAD of the fine root in middle-aged forest were significantly larger than the ones in mature-aged forest (P<0.05). However, in 70-90 cm (deeper layers) and 40-50 cm (shallower layers), the RLD and SAD of the middle-sized thick roots (5 mm<d<20 mm) and the thick roots (20 mm<d) in middle-aged forest, were significantly smaller than those in the mature-aged forest (P<0.05). (3) In the middle-aged forests, the root surface area, the root forks, the root fractal dimension, and the average branch angle were chosen as principal components in analyzing the root architecture. But the root volume, the root forks, and the average branch angle were chosen as principal components in mature-aged forest. The principal component analysis on the root order showed that the diameter class among 1-2 mm significantly influenced the SAD and the root volume. (4) There were no significant difference in the amount of the adventitious buds on cloning roots, the first-ordered lateral roots and branch angle between the two-age forests (P<0.05). (5) It was found that the amount of the adventitious bud on the second-ordered roots were 3-4 times more than that on the first-ordered roots by comparing the shoot bud on different root orders in the two-age forests. Based on the analyses on the trade-off of Populus euphratica root. Our result suggested that the fine roots (d<2 mm) would significantly affect the clone root architecture of Populus euphratica, and played an important role in the trade-off of Populus euphratica root function.