封育对华北落叶松低效人工林林下植被的影响

Effect of Closure for Nature Regeneration of Larix principis-rupprechtii on Understory Vegetation

以木兰围场国有林场40a左右生华北落叶松低效人工林为对象,采用样地、样方测定法研究了封育2a对不同抚育疏伐保留密度林分林下植物群落植物组成与结构的影响,结果是保留密度为825株·hm-2和500株·hm-2的低效人工林,经封育后林下植物种类及个体数量都增加,增加者主要为草本植物,增加量低密度林分高于高密度林分;灌木层平均高度和盖度增加,盖度增加幅度低密度林地大于高密度林地;高密度林地草本层优势种(批针薹草)不变,低密度林地原次优势种(小红菊)上升为优势种,而原先的优势种(金毛狗尾草)衰退为次优势;草本植物Margalef丰富度指数、Simpson指数、Shannon-Wiener指数、Pielou均匀度指数等4个物种多样性指数高密度样地和低密度样地都有相应提高,封育可以提高林分林下多样性,高密度林分提高幅度大于低密度林分;综合考虑,为改善林下植物群落结构,40a生左右华北落叶松低效人工林抚育改造适宜保留林分密度为500株·hm-2左右。

Larix principis-rupprechtii; forest of 40a in Mulan paddock state-owned forest farm was surveyed using sample plot and quadrat method to study the effect of two years closure of forest on the composition and structure of understory vegetation community. The result showed that density 825 plants per hm2 and density 500 plants per hm2 both increased understory vegetation species and quantities, mostly the herbal plants, the increment of which for low density forest were higher than for high density forest. Shrubs height and coverage were increased, with increment of coverage for low density forest to be higher than high density forest. For herbal vegetation the dominant species remain same in high-density forest and secondary dominant species went up to be dominant one. Of herbal vegetation of low-density forest, secondary dominant species went up to be dominant one while original dominant species went down to be the secondary dominant one. Species diversity indices like Margalef richness, Simpson index, Shannon-Wiener index, Pielou evenness index for both low-density forest and highdensity forest were all increased. The amount increased for high-density forest was bigger than that of low-density forest. Based on the above analysis, the density after tending should be kept as 500 plants per hm2 for Larix principis-rupprechtii of 40 a.