杉木人工林不同根序的一级根形态差异及其对间伐的响应

Variations of morphology among first order roots in different branch orders and the effect of thinning on its' morphology in Chinese fir plantation

以江苏南京溧水林场实施了4种间伐强度（CK（不间伐）、弱度间伐（LIT,比例30%）、中度间伐（MIT,比例50%）、强度间伐（HIT,比例70%））的25年生杉木人工林为研究对象,探讨了不同根序上一级根直径、根长和比根长的差异及间伐（6年）对其生长的影响。将一级根按着生位置的不同分为4类：Ar（2级根上的一级根）、Br（3级根上的一级根）、Cr（4级根上的一级根）、Dr（5级根上的一级根）。结果表明：杉木人工林不同根序上一级根数量和根长存在显著差异（p〈0.05）,而直径和比根长无显著差异（p〉0.05）。随着一级根着生根序的增加,一级根数量极显著减小（p〈0.01）,所占总根数比例从大到小为Ar（79%）〉Br（13%）〉Cr（6%）〉Dr（2%）;Dr类根的根长显著大于其余3类根的根长（p〈0.05）。与对照相比,间伐仅对Br类根的直径及Dr类根的直径和根长有显著影响（p〈0.05）。其中,Br类根的直径在LIT和HIT中显著减小;Dr类根的直径在MIT中显著增大,而根长却在LIT中显著减小。相关分析表明,土壤表层（0~10 cm）林下非目的树种活细根生物量、土壤亚表层（≥10~20 cm）全氮分别与Br类、Dr类根的直径呈显著的负相关关系,土壤表层（0~10 cm）的全氮则与Dr类根的根长呈显著正相关关系。

The number,diameter,length and sepecific root length（ SRL） of first order roots in different branch orders among four thinning intensities（ CK. 0,LIT. 30%,MIT. 50%,HIT. 70%） of Chinese fir（ 25years） plantation were studied in Nanjing Lishui Forest Farm of Jiangsu province. First-order root samples from plantations were separated into four categories： Ar（ from 2nd-order）,Br（ from 3rd-order）,Cr（ from 4th-order） and Dr（ from 5th-order）. Results showed that： The first order roots in different branch orders showed significant differences in numbers and root length（ p 0. 05）,whereas there were no significant differences observed in both root diameter and SRL. The numbers of first-order root in different root orders significantly increased with increasing root order（ p 0. 05） ： Ar（ 79%） Br（ 13%） Cr（ 6%） Dr（ 2%）. And Dr was significantly longer than the others in length（ p 0. 05）. Compared with the control plots,only the diameter of Br and Dr and the length of Dr had a significant response to thinning practice. The mean diameter of Dr significantly increased in MIT plot,but the length of it significantly decreased in LIT plot. The mean diameter of Br both LIT and HIT markedly decreased. Correlation analysis showed,the non-target live fine root in 0- 10 cm soil depth and soil total N in ≥10- 20 cm depth had a significantly negative effect on the diameter of Br and Dr,whereas a significantly positive relationship was observed between soil total N at 0- 10 cm depth and the root length of Dr.