立地管理措施对2代26年生杉木林生产力的影响

Effects of site management on the productivity of a 26-year-old second rotation Chinese fir plantation

为研究1代杉木林采伐后采用不同立地管理措施对更新的2代26年生杉木林生产力的影响,在1代20地位指数级的29年生杉木林(起源于本地普通杉木种子)中设置固定试验地,采伐后采用5种采伐剩余物处理方式和2代杉木种子园种子培育的苗木营造2代杉木试验林,研究造林后26 a 5种不同采伐剩余物处理对2代杉木人工林生产力的影响。结果表明,2代26年生杉木林平均蓄积量为666.312 m^(3)·hm^(-2),平均出材量为536.805 m^(3)·hm^(-2),年平均蓄积增长量为25.627 m^(3)·hm^(-2)·a^(-1)。不同处理的蓄积量和总材种出材量排序均为:保留采伐剩余物处理(BL2)>加倍采伐剩余物处理(BL3)>炼山处理(SB)>全树收获处理(BL1)>移除采伐剩余物处理(BL0),5种不同处理的大径材出材量均在65.52%以上,不同处理间蓄积量和出材量差异不显著。本试验的2代26年生杉木林并没有出现前人报道的连栽生产力下降的情况,且不同采伐剩余物处理之间的生产力也无显著差异。采伐后保留采伐剩余物、适地适树(杉木造林选择20以上地位指数级的林地)和采用经遗传改良的苗木造林是缓解杉木连栽地力衰退、维持杉木大径级无节材人工林可持续经营的有效途径。

The effects of different site management strategies on the productivity of a replanted second-rotation Chinese fir(Cunninghamia lanceolata)plantation were studied after establishing a fixed experimental site in a 29-year-old Chinese fir plantation(originating from ordinary local Chinese fir seeds)with a site index class of 20 in the first rotation.After harvesting the first rotation plantation,seedlings from a second-generation Chinese fir seed orchard were used to establish a second-generation Chinese fir experimental plantation that contained five different harvest residue treatments.The effects of the treatments on the productivity of second-generation Chinese fir forest plantation were studied at 26 years after establishment.The results showed that the average stand volume of the 26-year-old second rotation Chinese fir plantation was 666.312 m^(3)·hm^(-2),average timber output was 536.805 m^(3)·hm^(-2)and mean annual stand volume increment was 25.627 m^(3)·hm^(-2)·a^(-1).The stand volumes and timber output orders for the different treatments were as follows:stem and bark harvest treatment(BL2)>doubling slash treatment(BL3)>burning treatment(SB)>whole-tree harvest treatment(BL1)>removal of slash treatment(BL0).The quantity of large diameter wood produced after the five different treatments was over 65.52%;however,there were no significant differences among the five treatments.There was no productivity decline in the 26-year-old second-rotation Chinese fir plantation in this study,which differs from the results reported by previous studies.There were also no significant differences in productivity among the different harvest residue treatments,which may be related to factors such as a higher site index,sufficient soil nutrient reserves,and the use of genetically improved seedlings.The results suggest that retaining residues following stem and bark harvesting,matching species with the site(planting Chinese fir at 20 or higher site index class sites),and the use of genetically improved planting stock are effective ways to alleviate the problem of soil decline in Chinese fir over successive rotations and sustainably manage Chinese fir large-diameter knot-free timber plantations.