滇中云南松低质低效人工林疏伐的密度及生长动态研究

在滇中宜良禄丰村林场，以0、25.8％、31.5％和27.7％的株数疏伐强度对密度为7311、4933、6733株/hm2和4211株/hm2的4块30 m×30 m林龄25年生塘状直播造林的云南松人工林样地进行首次疏伐。疏伐后1.0a和5.3a时，进行每木调查，计算林分密度、活立木生长量和枯立木数量。结果表明，疏伐有效地促进了林木生长，其中：1）疏伐1.0 a和5.3 a后，样地1-4的林分密度降低至6744、3604、4579、2989株/hm2和3856、3000、4278、2611株/hm2；2）疏伐5.3 a后，样地1-4的林分平均胸径和树高分别从疏伐前7.7、6.2、8.1、8.9 cm和6.4、5.7、8.5、8.5 m，提高至9.6、9.6、10.3、11.0 cm和9.2、9.5、10.5、12.1 m；3）对照样地的蓄积量比疏伐后的增加13.6％，而疏伐样地2-4则分别增加156.8％、49.5％和37.5％，均高于对照。对照林分的枯立木高达55.0％，疏伐林分的为8.0％-19.6％，揭示了此类林分的实际疏伐强度还可以相应地提高。

Dynamic of Forest Density and Growth for Inferior Plantation Thinned of Pinus yunnanensis in the Centre Yunnan

In Lufengcun Forestry Centre of Yiliang County,the Centre of Yunnan,in a 25-year-old Pinus yun-nanensis plantation which regenerated by seeds directly sowed at a small spot of site preparation,the first thinning was implemented in four 30 m ×30 m sampling plots based 0.0%,25.8%,3 1.5%and 27.7%thinning intensity on densities of 7 311,4 933,6 733 and 4 211 tree/hm2. After 1.0-and 5.3-year of the forest thinned,tally was carried out,and forest densities,tree growth,dead standing trees were calculated. The results showed that the thinning effectively facilitated forest growth.Firstly,after 1.0- and 5.3-year of forest thinned,stands densities of 1 -4 sampling plots were declined to 6 744、3 604、4 579、2 989 and 3 856,3 000,4 278,2 611 tree/hm2,re-spectively. Secondly,after 5.3-year of stand thinned,mean diameters at breast height （DBH）and tree heights for 1 -4 sampling plots were increased to 9.6,9.6,10.3,11.0 cm and 9.2,9.5,10.5,12.1 m from which of 7.7,6.2,8.1,8.9 cm and 6.4,5.7,8.5,8.5 m,respectively,before stands thinned.Thirdly,compared to thinned stands,there was 13.6% increment of timber volume in the control sampling plot,while which were 156.8%,49.5% and 37.5% in 2 -4 thinned sampling plots,respectively,in terms of timber volume incre-ments of thinned stands overwhelmingly higher than which of unthinned stand.In 0.0%thinned forest,there was 55.0% dead standing trees,while in thinned forests,the valvue was 8.0%-19.6%.The results implied that practical thinned intensities could be properly increased in this kind of P.yunnanensis forest.