中文摘要：

林木细根（直径〈2 mm）拥有庞大而复杂的分枝系统,在森林生态系统养分循环过程中发挥重要作用,因此研究不同树种细根构型形态对树种地下生态位分离、共存和森林生态系统功能过程具有重要意义.选取川西亚高山3个优势树种——岷江冷杉（Abies faxoniana）、粗枝云杉（Picea asperate）和红桦（Butula albosinensis）,采用挖掘法采集完整的细根根系,依据根序分级方法,测定细根形态参数（直径、根长、比根长和比表面积）.结果表明：细根形态在不同根序间差异显著,3个树种细根直径、根长随根序的升高而升高,比根长和比表面积随序级的升高而降低.不同树种间细根形态也表现出极显著差异,岷江冷杉、粗枝云杉和红桦细直径变化范围分别为0.31-0.85 mm、0.29-0.65 mm和0.23-0.55 mm,两个针叶树种（岷江冷杉和粗枝云杉）直径与根长均大于红桦.红桦的比根长和比表面积则高于两个针叶树种.综上所述,低级别根吸收能力更强而构建消耗更低;红桦比岷江冷杉和粗枝云杉根系吸收能力更强.

英文摘要：

Forest fine roots （diameter 〈 2 mm） have large and complicated branch systems, which play an important role in nutrient cycling of forest ecosystem. Therefore, exploring root morphology of different tree species is helpful for understanding belowground processes of forest ecosystems. The fine roots of three dominant subalpine tree species （Abies faxoniana, Picea aspirate and Betula albosinensis） were collected in western Sichuan. Fine root branch order was classified according to Pregitzer＇s method. Fine root samples were scanned by Win-RHIZO system to analyze root morphology parameters, including diameter, length, specific root length （SRL） and specific root area （SRA）. The results showed significant differences in root morphology among branch orders. From the 1st to the 5t~ order of each tree species, root diameter and length became ever greater but SRL and SRA smaller. Regardless of the root order, significant differences in morphology were also observed among species. The diameter ofA. faxoniana, P. aspirate and B. albosinensis ranged from 0.31 mm to 0.85 mm, from 0.29 mm to 0.65 mm and from 0.23 mm to 0.55 mm, respectively. The diameters of two conifers were significantly greater than that of B. albosinensis. Similar performance was observed in root length. On the contrary, the SRL and SRA of B. albosinensis were obviously higher than those of other two coniferous species. Compared to higher root orders, lower root orders had stronger absorption capacity and lower construct cost. Additionally, compared to the roots of coniferous tree species, the roots of B. albosinensis had stronger absorption capacity.