不同林龄、径级杉木人工林种内竞争规律

Intraspecific competition in a Cunninghamia lanceolata plantation with different age and diameter classes

根据野外调查数据,提出了不同林龄和径级与竞争强度之间差异性的假设,运用Hegyi与距离有关的竞争指数模型进行分析,并探讨林龄及径级与竞争强度之间的关系。结果表明：杉木Cunninghamia lanceolata人工林种内平均竞争强度随着林龄的增加而逐渐减小,在10-25 a,平均竞争强度减小趋势较为明显,林龄大于25 a时,平均竞争强度下降趋势平缓;随着对象木径级的增加,平均竞争强度不断降低,当杉木径级在20 cm以内时,竞争强度变化显著,径级为20 cm以上时,竞争强度变化很小;平均竞争强度随林龄和径级增加而呈现的变化均可用指数函数表征IC=ae-bx;竞争强度与对象木胸径服从幂函数关系ICi=73.761 3D-0.978 3;方差分析显示,林龄和径级对平均竞争强度有极显著影响（P〈0.01）。杉木人工林种内竞争强度与林龄和径级之间存在密切关系,为科学有效地开展杉木人工林的经营和管理提供重要依据。

To test the hypothesis that stand age and diameter class in a Cunninghamia lanceolata plantation affected competition intensity, Hegyi＇s distance-dependent competition index model and analysis of variance（ANOVA） were used in the analysis for and discussion of the relationship between stand age, diameter class,and competition intensity. Results of the ANOVA demonstrated a highly significant effect（P〈0.01） of both stand age and diameter class on competition intensity. The average intraspecific competition intensity between10 and 25 years decreased with increasing stand age, and after 25 years continued to decrease but at a decreasing rate. With an increase in diameter class from 0-20 cm, the average intraspecific competition intensity also decreased, but it exhibited little variation when larger than 20 cm. The exponential function IC= ae-bx could be used to represent changes in competition intensity for stand age and diameter class with ICi= 73.761 3D-0.978 3. Thus, competition intensity was closely related to stand age and diameter class providing an important basis for scientifically and effectively carrying out the management of Cunninghamia lanceolata plantations.