Abstract:

Eucalyptus urophylla×E. Grandis is a typical plantation tree species in southern China. Understory plant diversity and its determinants are important basis for ecological restoration and naturalization of Eucalyptus urophylla×E. Grandis plantations. In order to analyze the variation trend and determinants of understory plant diversity in different ages Eucalyptus urophylla×E. Grandis plantations, the understory plant diversity and environmental factors in five different ages (1, 2, 3, 4, ≥5years) Eucalyptus urophylla×E. Grandis Plantations in Guigang were investigated. TWINSPAN and DCA were used to compare understory plant communities, and CCA was used to analyze the decisive environmental factors. The results showed that (1) the number of understory plant species increased in the first 3 ages plantations and then decreased. The highest understory plant diversity was found in 3-4 years plantation; (2) The understory plants of Eucalyptus urophylla×E. Grandis plantations showed a succession trend from the sunny drought-tolerant herbaceous community (represented by Poaceae and Dicranopteris linearis) to the sunny tolerant shrub community (represented by Rhodomyrtus tomentosa and Melastoma candidum) to the mesophyte community (represented by Eurya chinensis, Mallotus apelta and Ilex asprella) to the shade tolerant shrub community (represented by Evodia lepta and Schefflera octophylla); (3) Understory light transmittance and soil moisture were the most important environmental determinants of understory plant diversity, followed by soil capacity and soil organic matter content. The most important limiting factor for the ecological restoration and naturalization of Eucalyptus urophylla×E. Grandis plantations was the understory light transmittance. As long as appropriate thinning and artificial forest gaps are constructed, it will create good conditions for native plants settlement.

Key words: Eucalyptus urophylla×E. Grandis plantations, Understory diversity, Plant community, DCA, CCA, Determining factors

摘要：

尾巨桉（Eucalyptus urophylla×E. grandis）是中国南方人工林的典型树种,尾巨桉人工林林下植物多样性及影响因素是决定其生态恢复和自然化改造的重要基础。为探明不同林龄尾巨桉人工林林下植物多样性变化趋势及影响因素,选择广西贵港市1—5 a及以上尾巨桉人工林进行林下植物多样性和环境因子调查,运用双向指示种分析（TWINSPAN）和除趋势对应分析（DCA）对林下植物群落进行对比,通过典范对应分析（CCA）来分析影响植物多样性的主要环境因子。结果表明：（1）不同林龄尾巨桉人工林林植物多样性随林龄呈现先上升或下降的趋势,林龄3—4 a的林下植物生物多样性最高;（2）尾巨桉人工林林下植物群落呈现从以禾本科植物（Poaceae）和铁芒萁（Dicranopteris linearis）为代表的阳生耐旱草本植物群落—桃金娘（Rhodomyrtus tomentosa）、野牡丹（Melastoma candidum）为代表的阳生耐旱灌木群落—米碎花（Eurya chinensis）、白背叶（Mallotus apelta）、梅叶冬青（Ilex asprella）等为代表的中生灌木群落—三叉苦（Evodia lepta）、鸭脚木（Schefflera octophylla）等为代表的耐荫灌木群落的演替趋势;（3）林下透光率和土壤水分是尾巨桉人工林林下植物多样性的主要影响因素,土壤容量、土壤有机质含量等为次要影响因素。尾巨桉人工林的近自然化改造和生态恢复的最重要限制因素是林下透光率,只要适当间伐,人工构建一些林窗,将为乡土植物定居创造良好条件。

关键词: 尾巨桉人工林, 林下植物多样性, 植物群落, 除趋势对应分析（DCA）, 典范对应分析（CCA）, 影响因素