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

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 Western 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 × 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).