三峡库区桉树人工林封育后的群落特征和演替趋势

Characteristics and Succession of Eucalyptus Plantation after Closing for Afforestation in the Three Gorges Reservoir Area

为了解封育后桉树人工林的群落特征和演替趋势,以三峡库区中游地段世坪林场封育11年后的桉树人工林为研究对象,通过群落调查(样方法),分析了区系组成、群落外貌、垂直结构和主要种群年龄结构。结果显示,在4 800 m2样地中共记录维管植物(不含桉树)46科76属88种,科属分布型都以热带分布为主,但温带分布也占有一定比例;群落主要由具中小型革质全缘单叶的高位芽植物构成,但落叶树比例高于当地常绿阔叶林;群落层次分明,可分为乔木层、亚乔木层、灌木层、草本层;优势种巨桉(Eucalyptus grandis)更新不良,将会逐渐衰退,而杉木(Cun-ninghamia lanceolata)、丝栗栲(Castanopsis fargesii)和小红栲(C.carlesii)种群径级结构呈金字塔型,幼苗储备充足,为增长种群。通过分析桉树人工林的群落特征和主要种群年龄结构,认为封育后三峡库区桉树人工林处于向地带性常绿阔叶林演替过程中一个不稳定的过渡阶段,随着演替的进行,桉树的优势地位将逐渐为丝栗栲和小红栲等顶级树种所取代。

To analyze characteristics and succession of Eucalyptus plantation after closing for afforestation, the flora composition, physiognomy, community structure and size class structure of dominant species of Eucalyptus plantation after 11 years＇ closing for afforestation in Shiping, the Three Gorges Reservoir Area （TGRA） were studied by using community investigation method （quadrat method）. The results show that 88 species of vascular plants are recorded （ excluding Eucalyptus species） in 4800 m^2 plot, belonging to 76 genera and 46 families. The analysis of rioristic geographical elements indicates that the tropical elements are dominant but that temperate elements also exist in the community. Most of the plants in Eucalyptus plantation are phanerophytes with meso- and microphyllic-leathery simple leaves. The stratification of the vertical of Eucalyptus plantation is obvious. From the canopy to the forest floor, there are four distinct layers, namely tree layer, sub-tree layer, shrub layer and herb layer. The size class of dominant species Eucalyptus grandis indicates that it lacks saplings banks and regenerates poorly; the size class of Cunninghamia lanceolata, Castanopsis fargesii and C. carlesii shows positive pyramidal type, indicating that both of them have rich saplings banks and regenerate well. According to characteristics of Eucalyptus plantation and size class of dominant species, it suggests that Eucalyptus plantation in TGRA is an unstable transitional type in zonal evergreen broad-leaved forest succession process. With the succession of the community proceeding, the climax species such as C. fargesii and C, carlesii will substitute the dominant status of Eucalyptus spp.