混交比例对西南桦和红锥早期生长与竞争的影响

Effects of mixing ratio on early growth and competition of Betula alnoides and Castanopsis hystrix

【目的】探究混交比例对西南桦和红锥生长及其竞争状况的影响,为其合理混交配置进而实现其混交林高效培育提供理论依据。【方法】以广西凭祥6年生西南桦和红锥不同比例混交试验林为对象,开展1∶1、1∶3和1∶5(西南桦∶红锥)混交处理以及西南桦和红锥纯林的生长调查,采用Hegyi方法计算种内、种间竞争指数,对比分析各混交处理间林木生长及竞争差异,阐明林木生长与竞争的相关性。【结果】与纯林相比,各混交比例处理对西南桦的树高、胸径、冠幅、胸高断面积、冠长、树冠体积和树冠表面积均有显著促进作用;而对于红锥而言,仅1∶1混交处理的胸径、冠幅、冠长、冠体积和冠表面积显著高于纯林。混交林分内西南桦的种内竞争指数随红锥占比增大而显著下降,而红锥的种内竞争指数随红锥占比增大而显著增加;西南桦的种间竞争指数以1∶1混交比例处理为最高,而红锥的种间竞争指数以1∶3混交比例处理为最高。西南桦和红锥的种内竞争指数均与其自身的胸径、树高、冠幅、胸高断面积、冠长、冠体积、冠表面积呈显著负相关,与高径比、冠比率显著正相关;西南桦的种间竞争指数与其胸径、树高、枝下高、冠幅、胸高断面积、冠体积、冠表面积显著负相关,而红锥的种间竞争指数仅与树高呈负相关。【结论】综上所述,1∶1混交可作为我国南方地区西南桦与红锥混交林营建的推荐模式。

【Objective】The purpose of this study was to explore the effects of mixing ratio on growth and competition for Betula alnoides and Castanopsis hystrix,so as to provide evidences for rational mingling and further efficient management of their mixture.【Method】The growths of B.alnoides and C.hystrix were investigated in 6-year-old mix trial plantations in Pingxiang,Guangxi,which included five treatments:monoculture of each species and mixtures of B.alnoides and C.hystrix with ratio as 1:1,1:3 and 1:5.The intraspecific and interspecific competition index of both species were calculated with Hegyi’s competition model,the differences of tree growth and competition among these treatments were compared,and correlation between tree growth and competition was clarified.【Result】Compared with monoculture,the mixing treatments significantly promoted tree height,diameter at breast height(DBH),crown width(CW),basal area at breast height(BA),crown length(CL),crown volume(CV)and crown surface area(CSA)of B.alnoides;and for C.hystrix,DBH,CW,CL,CV and CSA of 1:1 mixing treatment were significantly higher than those of its monoculture.The intraspecies competition index decreased significantly for B.alnoides while increased for C.hystrix with increasing proportion of C.hystrix;the highest interspecific competition index were found in treatments of mixing ratio of 1:1 for B.alnoides and 1:3 for C.hystrix.The intraspecific competition indexes were in significantly negative correlation with DBH,tree height,CW,BA,CL,CV,CSA,and were significantly positively correlated with tree height to diameter ratio(H/D)and crown ratio for both species;and the interspecific competition indexes were significantly and negatively correlated with DBH,tree height,height to crown base(HCB),CW,BA,CV,CSA for B.alnoides,while were only in significantly negative correlation with tree height for C.hystrix.【Conclusion】As a whole,mixing ratio of 1:1 was recommended in the practice for establishing mixture of B.alnoides and C.hystrix in southern China.