中幼龄粗枝云杉(Picea asperata)根系的觅食能力

Root foraging ability of spruce(Picea asperata) in two growth stages

于四川省理县米亚罗林区选择幼龄期及中龄期两种生长阶段粗枝云杉个体为研究对象,采用挖掘法搜集全部根系,基于根系生物量及形态指标,从觅食器官总量角度定量衡量研究对象根系的觅食能力,并结合根序分级理论,基于前五级根序生理指标对其细根内部组分觅食效率进行评价,揭示其异质性规律.结果显示,9年、12年和29年生云杉侧根总生物量分别为154.50、2 195.27、7 380.60 g,总表面积分别为3 295.38、39 564.93、179 023.54 cm2,其中细根生物量依次为27.74、188.79、1 022.89 g,总表面积分别为2 353.97、19 395.49、98 551.54 cm2.根系比根长、总氮含量同根系觅食能力存在正相关关系.随着根序的增加,云杉前五级根系比根长、总氮含量呈显著下降趋势(P=0.000),因此,一级根至五级根根系觅食能力逐渐下降,细根内部组分觅食能力存在显著异质性.其中,一级根比根长和总氮含量远远大于其他根序,是云杉细根内部觅食能力最高的部分.云杉前五级根序非结构性碳水化合物(NSC)及其组分含量较低,随根序增加无显著变化规律,各根序自身NSC储量无法成为其觅食行为的主要能量供应源.上述研究结果为植物行为学研究,乃至森林地下生态学过程研究提供了基础数据,同时进一步丰富了对树木根系结构与功能的认识.

The extensive distribution and complex structure of the root system of woody plants in soil makes it difficult to understand its foraging ability. This paper aimed to quantitatively measure the foraging ability of the whole tree root system of spruce （Picea asperata）, the dominant tree species in the subalpine coniferous forests of western Sichuan, China, and to reveal the heterogeneity of foraging ability of fine root fractions. The whole root systems of three 9-year-old, three 12-year- old, and three 29-year-old spruce in two growth stages were excavated cautiously by hand. Based on the root biomass and root morphology index, foraging ability of whole root systems of the target plant was quantitatively expressed by the total amount of foraging organ; root foraging efficiency of internal components of fine root was evaluated by means of its physiological indices, including total N, total C, and non-structure carbohydrate （NSC）; the heterogeneity of foraging ability of fine root fractions was also clarified. The results showed a whole lateral root biomass of 154.5 g for the 9-year-old spruce, 2 195.27 g for the 12-year-old spruce, and 7 380.60 g for the 29-year-old spruce, with fine root biomass of 27.74 g, 188.79 g, and 1 022.89 g, respectively. There was an upward trend in the total length and in the total surface area of the whole lateral root systems or fine roots of spruce. The specific root length and total nitrogen content were positively correlated with root foraging ability. With the increase of root orders, specific root length, and total N content of the first five root order of spruce took on an upward trend. It suggested that the root foraging ability declined with the increase of root order, and there was significant heterogeneity among the internal components of fine root. The specific root length and total N content of the first order were far more than the other root orders, and the first order root foraging ability was the best among roots of all the first five orders. The nonstructural carbohydrates concentration and its fractions of the first five root orders were small, exhibiting no specific tendency, which suggested that the NSC stored in the first five root order was not enough for its foraging behavior. The physiological differences among growth stages showed that the age of tree had a significant impact on root physiological characteristics, and implied that with the increase of age of tree, the foraging efficiency of the first order root of spruce might decline. These conclusions enrich our understanding of the structure and function of root systems of woody olant at the nersnective of the root fora^in~, abilitv.