间伐保留密度对杉木人工林超大径材培育效果的影响OA

[Purpose]This study explored the effects of different thinning retention densities on the growth traits,timber species structure,and large-diameter timber yield in Chinese fir(Cunninghamia lanceolata)plantations,aiming to provide a basis for the efficient and targeted cultivation of large-diameter and super-large-diameter timber.[Method]A completely randomized block de-sign was adopted in a 28-year-old Chinese fir plantation in Yangkou State-owned Forest Farm in Fujian,with three thinning retention densities:low(300 plants·hm-2),medium(600 plants·hm-2),and high(825 plants·hm-2).The variations in stand growth,diameter-class structure,timber yield,and timber yield rate under different thinning retention densities were analyzed.[Result](1)Different thinning retention densities had no effect on tree height or its increment(P>0.05).As the thinning retention density decreased,the average diameter at breast height(DBH),average individual tree volume,and their increments increased(P<0.05),while the stand volume and its increment decreased significantly.Compared with the high-density treatment,the low-density treatment increased the average DBH and average individual tree volume by 12.93%and 27.43%,respectively,while decreasing the stand volume by 41.14%.(2)Thinning significantly promoted the shift of diameter-class distribution toward larger diameter classes across treatments.Among different treatments,the medium-density treatment showed the greatest volume increment in the conven-tional large-diameter timber range(26-36 cm),demonstrating the optimal stand-level yield advantage.The low-density treatment exhibited an absolute advantage in the yield of super-large-diameter timber(≥38 cm).(3)Different thinning retention densities had no significant effect on the yield rate of large-diameter timber.[Conclusion]Thinning can effectively promote the growth of o-ver-mature Chinese fir stands and the formation of super-large-diameter timber,whereas excessive thinning leads to a decline in total stand volume.Considering both yield and timber species structure,the medium thinning retention density(600 plants·hm-2)can effectively balance individual growth and stand volume,being an optimal retention density for cultivating large-diameter timber.The low thinning retention density(300 plants·hm-2)serves as an effective approach for the targeted cultivation of high-value super-large-diameter timber.