对不同林龄南方红豆杉[Taxus chinensis var. mairei (Lemee et Lévl.) Cheng et L. K. Fu]人工林不同等级细根的结构参数及 C 和 N 含量进行了比较,并分析了细根结构参数与 C 和 N 含量的相关性。 结果显示:不同林龄南方红豆杉Ⅰ ~ Ⅴ级 细 根 的 根 直 径、比根长( SRL)和比表面积( SSA)均有差异,6、7 和 8 a 植株细根的平均直径分别为 1. 073、1. 815 和 1. 734 mm,平均 SRL 分别为 14. 09、12. 88 和 14. 12 m· g^-1 ,平均 SSA 分别为 54. 93、45. 85 和50. 72 cm2 · g^-1 ;随根序等级提高,同龄植株细根的 SRL 和 SSA 均依次降低、根直径则逐渐增大,且总体差异显著(P<0. 05);总体上,除Ⅰ级细根外,7 a 植株各级细根的 SRL 和 SSA 均最小;6 a 植株各级细根的直径均最小。 各林龄植株细根的根尖密度和分叉数无显著差异(P>0. 05),但均以 6 a 植株最大。 细根干质量以 6 a 植株最低、7 a 植株最高,且差异显著。 随根序等级提高,细根 C 含量逐渐增加、N 含量则逐渐降低,同龄植株Ⅰ ~Ⅴ级细根的 C 和N 含量总体上差异显著;各级细根中,7 a 植株的 C 含量均最高、8 a 植株的 N 含量均最低; 6、7 和 8 a 植株细根的平均 C 含量分别为454. 41、501. 90 和441. 55 mg· g^-1 ,平均 N 含量分别为12. 63、11. 99 和5. 88 mg· g^-1 。 各林龄植株细根的 C 含量与细根直径和干质量均正相关,与 SRL、SSA 和根尖密度均负相关;N 含量与细根直径均负相关,与SRL、SSA 和根尖密度均正相关;此外,N 含量与干质量以及 C 和 N 含量与分叉数的相关性均无规律性。 研究结果表明:树龄对南方红豆杉细根直径影响较大,而不同序级细根的结构差异更明显。

Structure parameters and C and N contents of different grade fine roots of Taxus chinensis var. mairei (Lemee et Lévl.) Cheng et L. K. Fu plantation with different stand ages were compared, and correlation between fine root structure parameters and its C and N contents was analyzed. Results show that there are differences in root diameter, specific root length (SRL) and specific surface area (SSA) of Ⅰ-Ⅴ grades of fine roots of T. chinensis var. mairei with different stand ages, average root diameters of 6, 7 and 8 a plants are 1. 073, 1. 815 and 1. 734 mm, average SRL are 14. 09, 12. 88 and 14. 12 m· g^-1 , and average SSA are 54. 93, 45. 85 and 50. 72 cm2· g^-1, respectively; with enhanci grade, gradually, SRL and SSA of fine root of same age plants decrease while root diameter increases with generally significant difference ( P < 0. 05 ); in general, except Ⅰ grade fine root, SRL and SSA of different grade fine roots of 7 a plant all are lower than those of 6 and 8 a plants; root diameter of different grade fine roots of 6 a plant are the smallest. There are no significant difference (P>0. 05) in root-tip density and fork number among different age plants, but those of 6 a plant are the highest. Dry weight of fine root of 6 a plant is the lowest while that of 7 a plant is the highest with significant difference. With enhancing of root grade, C content in fine root increases gradually while N content decreases gradually. There are generally significant difference in C and N contents among Ⅰ-Ⅴgrade fine roots of the same age plant. In different grades of fine roots, C content in 7 a plant is the highest while N content in 8 a plant is the lowest; average C content of 6, 7 and 8 a plants is 454. 41, 501. 90 and 441. 55 mg· g^-1 and average N content is 12. 63, 11. 99 and 5. 88 mg· g^-1, respectively. In fine root, C content has positive correlation with root diameter and dry weight and negative correlation with SRL, SSA and root-tip density; N content has negative correlation with root diameter and positive correlation with SRL, SSA and root-tip density; furthermore, there is no regular correlation in N content with dry weight, in C and N contents with fork number. It is suggested that tree age has a stronger influence on fine root diameter of T. chinensis var. mairei, while it is more obvious in structure variation of fine root with different grades.