间伐施肥对杉木中龄林生长和材种结构的影响

Effects of thinning and fertilization on the growth and timber assortment structure of middle⁃aged Chinese fir forest

【目的】探讨不同间伐保留密度和施用不同比例N、P肥对杉木中龄林生长和材种结构的影响。【方法】在福建省洋口国有林场9年生立地指数22的杉木人工林中设置9块标准地,采用正交试验设计进行间伐和施肥的配套试验,间伐保留密度为1 200、1 500和2 250株/hm^(2),N肥施用量为0、100、200 g/株,P肥施用量为0、250、500 g/株,连续观测4 a。【结果】不同间伐密度和N、P肥施用量对杉木树高生长影响不显著,不同间伐保留密度对杉木林平均胸径增长有较大影响,最小密度与最大密度处理间存在显著差异。N肥施用量和P肥施用量对杉木林平均胸径增长影响较小,不同N、P肥施用量间差异不显著。不同间伐保留密度间平均单株材积增量存在显著差异,N、P肥施用量对平均单株材积增量影响较小。不同密度林分间蓄积量增量并不显著,但较高水平N、P肥施用量能促进林分蓄积量增量显著提高。低间伐保留密度显著影响杉木大径材出材量,而1 200株/hm^(2)保留密度下大径材出材量最高,1 500和2 250株/hm^(2)保留密度下能够获得较高的中径材出材量。高水平的N肥施用量能促进杉木中龄林大径材出材量的增加,高水平的P肥施用量能促进中径材出材量的增加,但其结果未达到显著水平。【结论】相对于N、P肥的施用效果,密度调控对杉木中龄林生长和材种结构的影响更为显著。较低的林分密度是培育杉木大径材的关键技术,而N、P肥施用效应需要长期观测。

【Objective】The effects of different thinning retention densities and different ratios of N and P fertilizers on the growth and timber assortment structure of middle⁃aged Chinese fir(Cunninyhamia lancelata)forests were analyzed.【Method】Nine standard plots were set up in a 9⁃year⁃old Chinese fir plantation with 23 site indices at the Yangkou National Forest Farm in Fujian Province.An orthogonal experimental design was used to carry out matching experiments of thinning and fertilization.The thinning retention density was 1200,1500 or 2250 trees/hm2;the N fertilizer application rate was 0,100 or 200 g per tree;and the P fertilizer application rate was 0,250 or 500 g per tree,this experiment lasted for four years.【Result】The results show that different thinning densities and N and P application rates had no significant effect on tree height growth.Different thinning retention densities had a greater impact on the average DBH growth of Chinese fir forests,and revealed a significant difference between the minimum density and the maximum density.The application rate of N fertilizer and P fertilizer had little effect on the average DBH growth of Chinese fir forest,and there was no significant difference between different N and P application rates.There was a significant difference in the average volume increase per plant among different thinning retention densities,and the application of N and P fertilizers had little effect on the average per tree volume increase.The increase in stand volume among stands of different densities was not significant,but higher levels of N and P application rates could promote a significant increase in stock volume increase.The low thinning retention density significantly affected the large⁃diameter wood yield,and it was highest under the retention density of 1200 trees/hm2.Higher yields of medium diameter timber were obtained at retention densities of 1500 and 2250 trees/hm2.A high level of N fertilizer application promoted an increased large⁃diameter wood output,while a high level of P fertilizer application promoted an increased medium⁃diameter wood output,but the result was not significant.【Conclusion】In general,compared with the application of N and P fertilizers,the effect of density regulation on the growth and timber structure of Chinese fir middle⁃aged forests is more significant.The lower forest density is key for cultivating large⁃diameter fir timber,and the effects of N and P fertilizer application require long⁃term observation.