马尾松人工林密度控制对林下植被多样性的影响

Effects of density management on understory plant diversity in plantation forests of Pinus massoniana

为研究不同造林密度对马尾松人工林林下植物多样性和土壤的影响,以江西省赣州市全南县小叶岽林场25年生4种不同抚育间伐林分密度(600、750、950、1150株·hm^(-2))控制措施后的马尾松人工林为研究对象,分析林下物种组成、植物多样性、优势物种重要值及土壤物理性质的变化规律。结果表明:间伐后第2年(2019年)和第3年(2020年),样地中物种组成共计49科93属122种;当林分密度为600~1150株·hm^(-2)时,林分密度越小,林下植被物种丰富度、Shannon-Wiener多样性指数、Pielou均匀度指数以及Simpson优势度指数普遍越高,并且随着年限的延长,林下植被多样性指数增大;2019—2020年间,木本层和草本层优势种变化不大,木本层均由冬青、大叶白纸扇、鼠刺、杉木以及檵木组成,草本层均由淡竹叶、细圆藤、铁芒萁、菝葜、铁角蕨和中华鳞毛蕨组成;当林分密度为600株·hm^(-2)时,土壤容重最低,土壤持水量最高,这表明低林分密度对马尾松林下土壤的物理结构具有改善作用。因此,600株·hm^(-2)是研究区25年生马尾松人工林的适宜林分密度,该林分密度有利于马尾松林的生长、群落稳定及可持续经营发展。

This study aimed to assess the effects of different silvicultural densities on the understory plants and soils of Pinus massoniana forests and to provide a theoretical basis for developing sustainable management plans.After the intermediate cutting of areas in 25-year-old Pinus massoniana plantations to four different densities(600,750,950,and 1150 tree·hm^(-2)),we analyzed changes in the species composition,plant diversity,important values of dominant understory species,and soil physical properties in pine plantations in the Xiaoyedong forest farm,Quannan County,Ganzhou City,Jiangxi Province.The results showed that during the period from November 2019 to November 2020,49 families,93 genera,and 122 species were found in the study plots.Within the range of 600-1150 tree·hm^(-2),the stand density was inversely correlated with the species richness,Shannon-Wiener diversity index,Pielou evenness index,and Simpson dominance index of the understory vegetation.Moreover,the diversity index of the understory vegetation also increased over time(i.e.,number of years).From 2019 to 2020,the dominant species in the woody and herb layers changed very little.The woody layer is composed of Ilex chinensis,Mussaenda esquirolii,Itea chinensis,Cunninghamia lanceolata,and Loropetalum chinense.The herb layer is composed of Phyllostachys glauca,Pericampylus glaucus,Dicranopteris dichotoma,Smilax china,Asplenium trichomanes,and Dryopteris chinensis.At a stand density of 600 tree·hm^(-2),the bulk soil density was the lowest,and the water-holding capacity was higher.This observation suggests that low stand density can improve the physical structure of soil in Pinus massoniana forests.Therefore,600 tree·hm^(-2) may serve as the optimal stand density,providing a reference for the growth and development,community stability,and sustainable management of Pinus massoniana plantations.