采用典型抽样法,以位于中亚热带的福建省将乐县的杉木[Cunninghamia lanceolata (Lamb.) Hook.]人工林为研究对象,对10、15、20、25、30 和40 a 林分的径级结构、林下植被组成以及物种多样性变化进行调查和分析。结果表明:不同林龄杉木人工林的径级结构均呈正态分布,均在接近平均胸径的径级上植株数量最多;径级和密度间的关系可以用3 参数的Gaussian 函数表征;不同林龄间胸径差异显著。杉木人工林林下分布有45 科80 属97 种植物,其中灌木层69 种、草本层28 种,物种丰富,但不同林龄的林分内各种类的重要值差异较大,且不同林龄的林分间优势种、共有种和独有种均明显不同。随林龄的增加,林下灌木层和草本层的物种组成、丰富度指数(R0 )、Simpson 多样性指数(D)和Shannon-Wiener 多样性指数(H’)、Pielou 均匀度指数(Jsw)和Alatalo 均匀度指数(Ea )均有明显变化。10 a 林分的林下物种数量最少(18 种),而20 a 林分的林下物种数量最多(40 种)。林下灌木层的D和H忆值分别为0. 827 ~ 0. 923 和1. 956 ~ 2. 917,且随林龄的增加均呈“上升—下降—平稳”的变化趋势;灌木层的Jsw和Ea值分别为0. 876 ~0. 959 和0. 686 ~0. 890,随林龄增加均呈“降低—升高—降低—升高”的变化趋势,且均在20 a 林分中最小、在25 a 林分中最大。林下草本层的D 和H忆值分别为0. 639 ~ 0. 898 和1. 274 ~ 2. 435,并随林龄增加均呈波动的变化趋势;草本层的Jsw和Ea值分别为0. 775 ~0. 949 和0. 663 ~0. 896,随林龄增加均呈“降低—升高—降低—升高—降低”的变化趋势,且均在15 a 林分中最小、在10 a 林分中最大。总体上看,林龄对杉木人工林林下灌木层和草本层的物种丰富度指数和多样性指数以及草本层的均匀度指数均有显著影响。根据研究结果,建议在杉木人工林的经营过程中对林下物种进行合理配置,并进行合理间伐,以促进林下植被的生长发育。

Changes in diameter class structure, vegetation composition of understory and species diversity of artificial forest of Cunninghamia lanceolata (Lamb.) Hook., with forest age of 10, 15, 20, 25, 30 and 40 a, located in Jiangle County of Fujian Province in mid-subtropical region, were investigated and analyzed by typical sampling method. The results show that diameter class structure of artificial forest of C. lanceolata with different forest ages all appears the normal distribution, and the largest individual number is at the diameter class close to average diameter at breast height (DBH); Gaussian function with three parameters can represent the relationship between diameter class and density; and difference in DBH among different forest ages is significant. There are 97 species in 80 genera of 45 families in understory of artificial forest of C. lanceolata, in which, there are 69 species in shrub layer and 28 species in herb layer. Species is abundant, while difference in important value of each species among stands with different forest ages is larger, and dominant species, common species and their own species among stands with different forest ages are obviously various. There are obvious changes in species composition, richness index ( R0 ), Simpson diversity index ( D), Shannon-Wiener diversity index (H’), Pielou evenness index (Jsw ) and Alatalo evenness index (Ea ) of shrub and herb layers in understory with increasing of forest age. Species number in understory of 10 a stand is the least (18 species), and that of 20 a stand is the most (40 species). D and H’values of shrub layer in understory are 0. 827 -0. 923 and 1. 956 -2. 917, respectively, and both appear the trend of “increasing - decreasing-stable”with increasing of forest age; Jsw and Ea values of shrub layer are 0. 876-0. 959 and 0. 686-0. 890, respectively, and both appear the trend of decreasing-increasing-decreasingincreasing” with increasing of forest age; Jsw and Ea values of shrub layer of 20 a stand are the smallest, and those of 25 a stand are the largest. D and H’ values of herb layer in understory are 0. 639-0. 898 and 1. 274-2. 435, respectively, and both appear the fluctuant trend with increasing of forest age; Jsw and Ea values of herb layer are 0.775-0.949 and 0. 663-0. 896, respectively, and both appear the trend of “decreasing-increasing-decreasing-increasing-decreasing” with increasing of forest age; and Jsw and Ea values of herb layer of 15 a stand are the smallest, and those of 10 a stand are the largest. In general, forest age has significant effects on species richness index and diversity index of shrub and herb layers and on evenness index of herb layer of understory of artificial forest of C. lanceolata. Based on above research results, it is suggested that rational allocation and thinning out species can promote growth and development of vegetation in understory during the process of management of artificial forest of C. lanceolata.