间伐的华山松＋云南松近成熟林密度及胸径断面积的变化研究

Study on Change of Tree Density,DBH and Basal Area of Pinus armandii and Pinus yunnanensis Mixed Forest during the Course of Maturing Treated by Intermediate Cutting

对宜良县禄丰村林场海拔高度1850m，于1954年起经营的华山松＋云南松混交林在其形成成熟林的50年生长过程中，就其采取间伐措施后林分中两树种林木株数（密度）胸径及断面积的变化进行了定位研究。通过立地条件相同地段设置的2块0．1hm^2的固定样地（其中，一块样地为继1978年后于1984年、1990年、1997年和2004年进行4次间伐的林分，另一块样地为未进行任何间伐活动，作为对照的林分）的林木30年（1978～2007年）的定位连续观测，其间伐和对照样地林分的林木密度分别从3070株·hm^-2和4400株·hm^-2降为580株·hm^-2和850株·hm^-2，林分的林木株数组成从华山松分别占91．9％和87．4％降至69．0％和49．4％，云南松从8．1％和12．6％上升至31．0％和50．6％，表明该地区较适宜云南松生长。在定位观测的30年间，无论混交林中的华山松或云南松林木的平均胸径，间伐林分始终大于对照林分；1978和2007年，间伐林分的林木胸高总断面积呈现几近相等（2403．9m^2·hm^-2与2384．9m^2·hm^-2），而对照林分林木的胸高总断面积则呈现较大幅度地降低（3260．0m^2·hm^-2与2988．6m^2·hm^-2），揭示了在华山松＋云南松混交林经营过程中间伐的必要性。

Taking the Pinus armandii and P. yunnanensis mixed forests established in 1954 at Lufengcun forest farm as study materials, the change of tree density, DBH and basal area of P. armandii and P. yurmanen.sis were studied. Two fixed sampling plots of 0. 1 hm^2 were set in the forest, one plot was treated with four times of intermediate cutting in 1984, 1990, 1997 and 2004, respectively ; whereas the other plot was not treated with mtermealate cutting. Through the fixed positioning observation of 30 years, it was found that in the plot with intermediate cutting, the tree density decreased from 3 070 stems/hm^2 to 580 stems/hm^2, the percentage of P. armandii decreased from 91.9 % to 69.0 %, the percentage of P. yunnanensis increased from 8.1% to 31.0 %. In the plot without cutting treatment, the tree nubmer decreased from 4 400 stems/hm^2 to 850 stems/hm^2, the percentage P. armandii decreased from 87.4 % to 49.4 % , the percentage of P. yunnartensis increased from 12.6 % to＇50. 6 %. The resuits indicated that the study site was suitable for growing P. yunnanensis. The study results also showed that, the DBH of trees in stand with intermediate cutting were higher than the trees in stand without intermediate cutting treatment. In 1978 and 2007, the total basal area of trees at breast height of stand with intermediate cutting were quite similar with 2 403.9 m^2/hm^2 and 2 384. 9 m^2/hm^2, respectively; In the stand without intermediate cutting treatment, the basal area decreased from 3 260. 0 m^2/hm^2 to 2 988.6 m^2/hm^2. This study results implied the importance of intermediate cutting in management of P. armandii and P. yunnanensis mixed forest.