我国东北国有林区森林资源结构变化及经营研究

研究我国东北国有林区近20 a的森林资源结构变化情况.结果表明:作为我国重要的木材生产基地,虽然该区森林资源总量有所增加,面积和蓄积占全国森林面积和蓄积的比例达到13%和18%,但林种结构、树种结构变化极大,用材林面积比例仅为31.45%,而防护林和特用林占68.55%;落叶松和桦树占51%,水曲柳等珍贵树种仅占2.72%;森林质量严重下降,林分平均胸径逐渐降低,仅为13.2 cm,平均郁闭度0.61;第八次清查与第七次清查相比,虽然林木采伐总量下降了6.84%,但采伐发生面积却增加了35.12%,原因是采伐小班每hm2出材量下降了42.76%;采伐65%发生在中幼龄林,采伐量占总量的46%,而中小径材量比重达到47%.一些林区已经无材可采,中、小径级采伐量已占采伐量的52%,林相越来越稀疏,采伐径阶越采越小的隐患明显.科学的森林经营措施是加大珍贵树种资源培育,加强森林采伐监管,合理划分林种结构,坚持调减采伐量,使森林资源得到较长时期的休养生息.

Structure Change and Management of State-Owned Forest Resources in Northeast China

The structure changes of state-owned forest resources in Northeast China were studied based on survey data of 20 years. As the important timber production area in China,Northeast China had the total amount of forest resources increased including the forest area and volume with the proportion 13% and 18% respectively. But thestructure of forest and tree species changed significantly. The ratio of timber forest was only 31. 45%. However, the shelter forest and special forest accounted for 68. 55%. But 51% of the forest was Larch and birch,ash tree and other precious species 2. 72%. The forest quality declined seriously with only 12. 3 cm of DBH and 0. 61 ofaverage canopy density. Compared the eighth national forest inventory with the seventh inventory,the total harvest of forest volumes declined 6 . 84%,but the total harvest forest areas increased 35 . 12%. The volume output per hectare fell 42. 76% because young forest accounted for 65% for this harvest. And the proportion of middle andsmall diameter forest proportion reached 47%,with DBH and average canopy density declined. Therefore,the following countermeasures were proposed,increasing the ratios of precious forests,strengthening forest harvesting regulation,optimizing the forest structure,deciding the optimal annual forest felling volume and rehabilitating the forest in a long period for northeast forest of China.