青冈栎林分空间结构对林下更新的影响

林分空间结构会显著影响其林下幼树更新。为明确其影响林下幼树更新的关键因子,以湖南省青羊湖国有林场青冈栎林天然次生林为研究对象,测量幼树株数密度、树高、地径和冠幅,计算混交度、大小比数、开敞度指数以及聚集指数代表林分空间结构,评价林下幼树更新情况,并用灰色关联度分析方法探究两者间的相关关系。结果表明,青羊湖国有林场13块青冈栎林样地林下更新幼树有6种,分属于4科5属,分别是青冈栎、苦槠、多脉青冈、南酸枣、黄檀、马尾松,青冈栎在更新幼树中占明显优势,是优势树种,幼树重要值为63.09%。青冈栎林各林分空间结构指数与林下更新指数均大于0.5,关联度较高,综合所有林分空间结构指数对林下更新指数关联度的均值来看,对林下更新的影响由大到小为大小比数>开敞度>聚集指数>混交度,大小比数对青冈栎林下更新影响最为显著。在促进青冈栎天然次生林林下更新时,应以调整林木大小分化程度为主,综合考虑林木空间分布格局的调整方案。

The Influence of Spatial Structure of Cyclobalanopsis glauca Forest on Understorey Regeneration

Forest spatial structure has a significant influence on the regeneration of saplings. To clarify the key factors affecting the regeneration of saplings, the natural secondary forest of Cyclobalanopsis glauca forest was taken as the research object in Hunan Qingyang Lake State-owned Forest Farm. The density, tree height, ground diameter and crown width of saplings were measured, and the mixing degree, size ratio, opening index and aggregation index were calculated to represent forest spatial structure. The regeneration of saplings under the forest was evaluated and the correlation between them was explored by using the grey relational analysis method. The results show that there are 6 species of undergrowth regeneration saplings in 13 sample plots of C. glauca forest in Hunan Qingyang Lake State-owned Forest Farm, belonging to 4 families and 5 genera, which are C. glauca, Castanopsis sclerophylla, C. multinervis, Choerospondias axillaris, Dalbergia hupeana and Pinus massoniana. C. glauca is the dominant species in regeneration saplings, and the importance value of saplings is 63.09%. The spatial structure index and undergrowth regeneration index of each forest spatial structure of C. glauca are greater than 0.5, indicating a high correlation degree. Based on the mean correlation degree of all forest spatial structure indexes to undergrowth regeneration index, the order of influence on undergrowth regeneration is size ratio> openness> aggregation index> mixing degree, and size ratio has the most significant influence on undergrowth regeneration of C. glauca. Therefore, to promote undergrowth regeneration of natural secondary forests of C. glauca, we should adjust the size differentiation degree of trees, and consider the spatial distribution pattern of trees comprehensively.