干扰对辽东山区次生林植物多样性的影响

Effects of disturbances on plant species diversity of secondary forest in montane regions of eastern Liaoning Province.

依据林分距离居民区和一、二级道路的远近以及郁闭度与受害乔木株数百分比,将人为干扰和自然干扰各划分为低度干扰、中度干扰和高度干扰3个水平.在此基础上,调查分析了干扰对辽东山区次生林植物多样性的影响,初步探讨了人为干扰和自然干扰影响的差异.结果表明,在不考虑次生林类型的前提下,受中度水平人为干扰的次生林总体多样性高于其它两个水平,从低水平干扰到高水平干扰的Simpson指数分别为0·95、0·96和0·92,Shannon-Wiener指数分别为3·60、3·77和3·36;乔木层多样性有随干扰水平提高而增加的趋势,灌木层和草本层的变化趋势与总体多样性相似;各次生林类型总体多样性随干扰水平的变化存在差异,且乔木层、灌木层和草本层的多样性变化在各次生林类型中未呈一致的趋势,其中灌木层和草本层受干扰影响较大;自然(雪/风)干扰发生近3年后,受到不同程度影响的桦木林总体多样性差异不大,Simpson指数分别为0·91、0·91和0·92,Shannon-Wiener指数分别为2·30、2·93和2·89;随着干扰水平提高,乔木层和灌木层多样性呈增加趋势,草本层多样性则变化不大.

According to the distance from forest stands to residential area and the first and second grade roads, as well as the canopy density and the percentage of damaged trees, this paper defined the disturbances, anthropogenic and natural, as low, medium and high levels. On the basis of this, the effects of different level disturbances on the plant species diversity of secondary forest in montane regions of eastern Liaoning Province were analyzed, and the differences between the effects of anthropogenic and natural disturbances were discussed. The results showed that without considering forest types, the overall plant species diversity of secondary forest under medium level anthropogenic disturbance was higher than that under low and high level anthropogenic disturbances, with the Simpson indexes being 0. 96, 0. 95 and 0.92, and Shannon-Wiener indexes being 3.77, 3.60 and 3.36, respectively. The diversities of shrub and herb layers were also the highest under medium level anthropogenic disturbance, while the highest diversity of arbor layer was appeared under the high level one. Among different forest types, there existed differences in the plant species diversity under anthropogenic disturbances, e. g. , the diversity under medium level anthropogenic disturbance was the lowest in hard broad-leaved forests, but the highest in other forest types. In all test forest types, no consistent tendency was observed in the changes of three layers＇ diversities with anthropogenic disturbance levels, but the diversities of shrub and herb layers were greatly affected by the disturbances. After 3 years of snow/wind damage, there was no distinct difference in the diversities among the birch forests under low, medium and high level natural disturbances, with the Simpson indexes being 0. 91,0. 91 and 0. 92, and the Shannon-Wiener indexes being 2. 30, 2.93 and 2.89, respectively. The diversities of arbor and shrub layers were both increased with the enhancement of natural disturbances, but there was no great difference in the diversity of herb layer among the three levels of natural disturbances. At present, anthropogenic disturbance mostly occurred in understory, while snow/wind damage occurred in canopy. Such dissimilarity could make the effects of environmental factors on plant species diversity differed greatly.