间伐对川西亚高山粗枝云杉人工林细根生物量及碳储量的影响

Effects of thinning on fine root biomass and carbon storage of subalpine Picea asperata plantation in Western Sichuan Province, China

以川西亚高山50年生粗枝云杉(Picea asperata)人工林为研究对象, 探讨了间伐对粗枝云杉人工林1-5级细根生物量及碳储量的影响。结果表明: 粗枝云杉人工林细根生物量和碳储量随根序等级的增加而显著增加(p < 0.05), 5级根序中1级根生物量及碳储量最小, 5级根生物量及碳储量最大。与对照(间伐0%)相比, 间伐对粗枝云杉人工林林分细根生物量及碳储量有显著影响(p < 0.05); 而对单株细根生物量影响不一, 间伐10%和20%与对照没有显著性差异(p > 0.05)。间伐显著影响生物量在各根序中的分配, 随着间伐强度的增加, 1、2级细根中生物量分配比例增加, 1级细根的生物量增加幅度最大; 3–5级细根的生物量分配比例减小, 5级细根减少幅度最大。其中, 间伐50%显著减少了细根在下层(20-40 cm)土壤中的生物量比例(p <0.05), 但与间伐20%和30%无显著差异(p > 0.05)。

Aims Fine root carbon storage is an important part of forest ecosystem carbon pools. Our objective was to determine the effects of thinning on fine root biomass and carbon storage in a Picea asperata plantation in Westem Sichuan Province, China. Methods We sampled fine roots of a 50 year-old P. asperata plantation thinned by different treatments in August 2010. We excavated soil blocks of 20 cm 20 cm x 20 cm to sample intact fine root branches of at least the first five branch orders, dissected the intact root branches by order and measured the biomass and carbon storage of each order. Important findings Fine root biomass and carbon storage significantly increased with root order （p 〈 0.05）. The first order roots had the smallest biomass and carbon storage, and the fifth order roots had the largest. Compared with the control, thinning the plantation had significant effects on fine roots biomass and carbon storage （p 〈 0.05）, while the effects of fine roots biomass per plant varied. Thinning treatments of 10% and 20% were not significantly different from the control （p 〉 0.05）. Thinning significantly affected the distribution of fine root biomass in the five root orders. As the thinning intensity increased, the ratio of biomass distribution in the first and second fine order increased. The first order had the largest increase. The ratio of biomass distribution in orders 3 to 5 decreased, and order 5 had the largest decrease. The 50% thinning significantly reduced the fine root biomass ratio in the lower soil layer （20-40 cm）, but there was no significant difference compared with 20% and 30% （p 〉 0.05）.