杉木林分密度对套种闽楠树型、光合能力及生物量分配的影响

[Objective]To investigate the change law of the tree type structure,leaf photosynthesis,and biomass allocation patterns of Phoebe bournei planted under different densities of Chinese fir plantations,and to provide scientific basis for precision transformation and improvement of the quality of nearly mature Chinese fir.[Methods]A 21-year-old Chinese fir plantation was selected as the study subject.Four thinning treatments with residual densities of 375 trees/hm2,570 trees/hm2,630 trees/hm2,and 810 trees/hm2 were set up,respectively.Underneath the Chinese fir plantation,900 trees/hm2of P.Bournei were planted to form a mixed canopy.The differences in growth indices,such as crown shape,side branch length,branching angle,leaf phenotype,chlorophyll fluorescence parameters,SPAD value,and root,stem,and leaf biomass of various organs,were measured and analyzed to determine the effects of stand density on the growth patterns of P.bournei.[Results](1)Under the 570 trees/hm2 Chinese fir plantation density,the crown height primary side branch length,and branching angles with secondary side branches of P.bournei were significantly larger than in other Chinese fir density treatments.Under the 375 trees/hm2 Chinese fir plantation density,the secondary side branch length and density of the primary and secondary side branches were also significantly greater than in other Chinese fir density treatments.(2)The leaf area and specific leaf area of P.bournei increased with increasing stand density of Chinese fir.The lower canopy leaves of P.bournei had significantly larger leaf length,width,area,and specific leaf area than upper canopy leaves.Under lower Chinese fir plantation densities(375 trees/hm2 and 570 trees/hm2),the chlorophyll fluorescence parameters and SPAD values of P.bournei leaves were lower than at other stand densities.(3)Under Chinese fir plantation densities of 375 trees/hm2 and 570 trees/hm2,the total leaf biomass,side branches,stem biomass,and total leaf biomass of P.bournei were all significantly greater than at other stand densities.(4)Under lower Chinese fir plantation densities(375 trees/hm2 and 570 trees/hm2),it is a significant positive correlation between the crown height and lateral branch biomass of P.bournei.Under higher Chinese fir plantation densities(630 trees/hm2 and 830 trees/hm2),there is a negative correlation between the crown height and total leaf biomass of P.bournei.[Conclusion]When the residual density of the near-mature Chinese fir stand is low,the growth of P.bournei is better,and it is beneficial for biomass accumulation and lateral branch growth in P.bournei.However,in a denser Chinese fir plantation environment,P.bournei leaves can enhance their light-capturing ability and maintain normal growth by increasing leaf length,decreasing specific leaf area,and increasing SPAD values.