不同林龄南方红豆杉人工林细根结构及C和N含量比较与相关性分析

Comparison on structure and C and N contents of fine root and their correlation analysis of Taxus chinensis var.mairei plantation with different stand ages

对不同林龄南方红豆杉也Taxuschinensisvar.mairei（LemeeetL＆#233;vl.）ChengetL.K.Fu页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-吁级细根的根直径、比根长（SRL）和比表面积（SSA）均有差异,6、7和8a植株细根的平均直径分别为1.073、1.815和1.734mm,平均SRL分别为14.09、12.88和14.12m·g-1,平均SSA分别为54.93、45.85和50.72cm2·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,7a植株各级细根的SRL和SSA均最小；6a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6a植株最大。细根干质量以6a植株最低、7a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,7a植株的C含量均最高、8a植株的N含量均最低；6、7和8a植株细根的平均C含量分别为454.41、501.90和441.55mg·g-1,平均N含量分别为12.63、11.99和5.88mg·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 L＆#233;vl.） 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） ofⅠ- 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 enhancing of root 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 ofT. chinensis var. mairei, while it is more obvious in structure variation of fine root with different grades.