热带北缘地区种植桉树前后林下植被的变化

分析我国热带北缘地区炼山营造的桉树(Eucalyptus)人工林前后林下植被物种组成与生长的差异,初步探讨桉树与林下植被的关系,为我国热带地区的桉树种植提供参考。造林前的植被包括3个马尾松(Pinus massoniana)林和1个果树林,炼山后全部种植桉树。结果表明:炼山造林2 a后,林下植被得到恢复,其种类组成没有发生改变,而频度的变化则与植物类型有关,频度减小的以灌木为主,频度增大的以草本为主。果树林改造为桉树林后,林下植被出现了一些新的物种,且物种平均高度大幅增加;马尾松林改造为桉树林后,多数物种的平均高度和盖度接近原有群落的水平,而芒萁(Dicranopteris dichotoma)从林下植被层消失,割鸡芒(Hypolytrum latifolium)盖度大幅提高,表明种植桉树对林下植被的影响因物种而异。经过炼山造林,在广东省茂名地区种植桉树对少数物种影响较大,短期内没有降低林下植被的多样性,长期是否存在影响还需要进一步观察。

Change of Understory before and after Planting Eucalyptus in the Northern edge of Tropical Area, Maoming, China

In order to figure out the relationship of Eucalyptus and understory plants, the differences of understory species composition and growth between Eucalyptus plantation and original vegetations were studied by afforesting after controlled burning. The original vegetation included 3 Pinus massoniana stands and an orchard. The results showed that understory species composition in Eucalyptus plantation after 2 years of restoration was the same of that in original vegetation. The frequency changed differently with species, by reducing for shrub species and increasing for herbaceous species mainly. Some new species appeared with fruit stands shifting to Eucalyptus plantation, and the average height of understory species increased a lot. The average height and coverage of most understory species in Eucalyptus plantation were close to that in original P. massoniana stands 2 years later, with Dicranopteris dichotom a disappeared and higher coverage of Hypolytrum latifolium. Understory species diversity in Eucalyptus plantation in the short-term did not change, but should be studied more in the long-term.