低密度造林对杉木生长、形质和材种结构的影响

[目的]对江西大岗山地区低密度杉木人工林自然稀疏进程、林木生长进程、形质特征、材种结构和经济效益动态变化特征进行调查分析,为杉木低密度造林调控管理提供科学依据.[方法]以2 500株/hm2传统造林密度为对照,对设立在江西省分宜县初植密度为1 111、1 667株/hm2的2种低密度杉木试验林生长发育规律进行了 25 ...

Effects of low stand density afforestation on the growth,stem-form and timber assortment structure of Cunninghamia lanceolata plantations

【Objective】 The goal of this study was to clarify the growth process, shape, quality characteristics, timber species structure and dynamic change characteristics of the economic benefits of low-density Cunninghamia lanceolata plantations in the Dagangshan area of Jiangxi Province. 【Method】 Using the traditional planting density of 2 500 individuals/hm ² as the control, the growth and development of two low-density Chinese fir experimental forests with an initial planting density of 1 111 and 1 667 individuals per hectare in Fenyi County of Jiangxi Province were monitored and analyzed for 25 years. 【Result】 The average tree height, average diameter at breast height (DBH), under branch height, and stock volume increased with stand age and decreasing densities. The average DBH of different stand densities at 19-25 years of age differed significantly, and the height under branches and volume increased the fastest at 8-19 years and 22-25 years of age, respectively. The results showed that the degree of natural differentiation increased with an increase in forest age and decreased with a decrease in densities. The cumulative withering rate was 25 years, and the difference between densities was significant. The average crown width of trees first increased, then decreased, and then increased slowly with an increase in age, and reached significant differences among densities at 19 years old. The annual average sparse rate and degree of crown overlap of natural lines first increased and then decreased slowly with an increase in forest age; the annual average natural sparsity rate reached a maximum value at 22 years of age, and the canopy overlap degree reached a maximum value at 8 years of age. The difference between the densities was significant. At 25 years, the breast height form ratio and heartwood ratio of 1 111 individuals per hectare and 1 667 individuals per hectare were higher than 2 500 individuals per hectare , and the rate of broken shoots, ratio of height to diameter, and young-adult wood ratio were lower than 2 500 individuals per hectare , and the difference in the height diameter ratio density was significant. At the near mature age of 19-25 years, the proportion of large diameter trees and volume of large-diameter timber increased with the decrease in stand densities, and 1 111 individuals per hectare and 1 667 individuals per hectare occurred in this period. The results showed that the total volume, total timber output, and economic timber output of the low-density stands were close to 2 500 individuals per hectare , and the total volume, total timber output, and economic timber output of 1 667 individuals per hectare stand exceeded 2 500 individuals per hectare at 25 years, respectively. The economic benefit analysis showed that the net income and net present value of the 1 667 individuals per hectare stand were the highest, which were 1.09 and 1.10 times higher than those of the 2 500 individuals per hectare , respectively, whereas 1 111 individuals per hectare had the highest benefit-cost ratio and internal rate of return, which were 7.35 and 30.20%, respectively. 【Conclusion】 The initial planting density of 1 111 individuals per hectare and 1 667 individuals per hectare can be selected and applied in the plantations of Cunninghamia lanceolata in the Dagangshan area of the Jiangxi Province.