间伐对杉木低效林生物多样性及土壤养分的影响

以15年生杉木低效林为研究对象,设计间伐强度为20%(T20)、30%(T30)、40%(T40)及未间伐(T0)4种间伐处理,探讨间伐2年后杉木林下生物多样性及土壤养分的变化,并采用改进层次分析法对间伐成效进行综合评价。结果表明:(1)间伐对林下植物生长具有积极的促进作用,有效提高林分的生物多样性,且林下植物种类、灌木层Simpson指数和Shannon-Weiner指数随着间伐强度增大而增加,T0、T20、T30和T40处理林下分别出现0种、12种、14种和16种植物;(2)间伐有利于改善土壤养分状况,间伐后杉木林土壤有机质含量、全磷含量、全钾含量和水解氮含量增幅依次为2.20~38.08 g·kg-1、0.19~0.98 g·kg-1、6.36~13.99 g·kg-1和19.13~154.19 mg·kg-1;(3)综合评价得到T0、T20、T30和T40处理的间伐成效指数值依次为0.294、0.503、0.724和0.732,说明T30、T40处理的间伐成效要明显好于T20处理。因此,建议对密度较大的杉木低效林按照30%~40%的株数间伐强度进行间伐改造,并保留阔叶树种,以形成多树种、结构比较稳定、生态和经济效益更高的针阔混交林,实现可持续经营。

Effect of thinning on biodiversity and soil nutrient in the low-benefit Chinese fir forest

The effects of four thinning intensities 20 ％ (T20),30 ％ (T30),40 ％ (T40) and the control (T0)] on the changes of biodiversity and soil nutrient in a 15-year old low-benefit Chinese fir forest were investigated.A modified hierarchical analysis was used to comprehensively evaluate the effect of thinning two years after the treatment.The results showed that:(1) Thinning promoted the growth and biodiversity of understory plants.The understory species number,Simpson and Shannon-Weiner index in shrub layer increased with an increase of the thinning intensity.The understory plant species numbers were 0,12,14 and 16 in T0,T20,T30 and T40,respectively;(2) Thinning improved the soil nutrient.Soil organic matter,total P,total K and hydrolytic N increased to 2.20-38.08 g·kg-1,0.19-0.98 g·kg-1,6.36-13.99 g·kg-1 and 19.13-154.19 mg·kg-1,respectively.(3) A comprehensive evaluation showed the effect index of thinning for T0,T20,T30 and T40 was 0.294,0.503,0.724 and 0.732,respectively,suggesting that T30 and T40 had better effects than T20.Therefore,thinning intensity of 30％-40％ should be recommended for the high density and low-benefit Chinese fir forest,and broad-leaf trees should be retained to form a stable multi-species and mixed broadleaf-conifer forest with high ecological and economic benefit to achieve the sustainable forest management.