杉木连栽幼林生长量、营养元素和土壤肥力的比较

结果表明：杉木连栽引起林地肥力减退，土壤地力衰退程度与前茬林生长周期有关。头茬杉木林周期短（14a）的二耕土上连栽的杉木长势较好，头茬杉木林周期长（24a）的二耕土上连栽的杉木幼树长势极差。林地施肥后并没有促进杉木幼树恢复生长。原因在于杉木幼树根系受到土壤中有毒物质毒害，根系腐烂，不能从土壤中吸收养分。建议采取生物工程措施解决杉木连裁地力减退问题。

Studies on Young Trees Growth, Elements Content of Leaves and Soil in Continuecl Planting Chines Fir

The results showed that successive cultivating chinese fir in the same land can cause degradation of forest land's fertility an degraded extent of its soil produetivity is related to growth periodicity of pre-stubble forest. When frist stubble forests for chinese fir have short periodicity(i. e. 14 years),the chinese fir continously-cultivated in the secondly-cultivated soil have a fair good growth vigour; when have long periodicity(i. e. 24 years),the same kind of juvenile chinese fir have a extremely inferior growth vigour,and after-fertilizing can not promote recovery of juvenile chinese fir's growth. It was because the root system of juvenile chinese fir were poisoned by toxic substance from soils,which further cause their rot and make it no uptaking nutrient from the soil. To solve problems from degradation of soil productivity owing to successive cultivation for chinese fir,their suggestion is to take bioengineering measure.