关键词: 桉树人工林, 物种多样性, 群落结构, 动态变化

Abstract: 【Objective】 To study the dynamic characteristics of species diversity and community structure in the shrub and grass layers of E. plantation, so as to provide reference for the stability maintenance of E. plantation ecosystem and sustainable development of forestry economy. 【Method】 Taking E. plantation in sichuan province as the object, the spatial sequence was used to replace the time series and the typical plot method to study the dynamic changes of species diversity and community structure in the undergrowth and grass layer of five E. plantations (4 a,5 a,6 a,7 a,8 a). 【Result】 ①A total of 210 species of vascular plants were recorded, belonging to 154 genera of 80 families. The total number of species in 4-8 a shrub and grass layers was reduced by 1/4, and the change rate of plant number was -24.3%. 4 a and 8 a had few species, In the middle three years (5-7 a), vegetation grew well. At 5 a, the number of genera of the family of the shrub and herb layers reached the peak of the evolution sequence.②The dominant species in the community evolved from light and wet to shade and barren, and Paeonia delavayi and Miscanthus floridulus, as established species, existed stably in the shrub and herb layers for a long time respectively. ③The species diversity of understory maintained an optimal level during the period (5-7 a), and the species richness index (D) and Shannon diversity index (H) in the shrub and grass layers were not consistent with the dynamic changes, but both reached the peak at 5 a. The Simpson dominance index (H') and Pielou evenness index (J_SW) were opposite to each other. ④The average density of shrub and grass layers increased first and then decreased with the increase of age; The average height fluctuates slightly over 5 years, but generally increases. ⑤The increase of E. density within a certain range was conducive to the improvement of species diversity in the shrub and herb layers, while the forest age,canopy density, average chest diameter and average tree height were significantly or significantly negatively correlated with the growth of undergrowth vegetation. 【Conclusion】 Species diversity and community structure stability of undergrowth shrub and herb layer of E. plantation changed. In the middle three years (5-7 a), species richness and community stability were the best, and inter-species, intra-species competition and tree layer structure changes were the main influencing factors.

Key words: Eucalyptus robusta plantation, species diversity, community structure, dynamic change