天目山不同海拔毛竹伐除区群落结构变化

以浙江天目山不同海拔(480、580、700和800 m)的毛竹伐除区森林植被为对象,基于群落生态学方法研究2017—2020年各海拔群落的结构变化。结果表明: 2017年所有样地木本植物有515株,隶属于27科43属50种。3 年间增加14科23属30种,个体数量增加116.9%,新增物种主要有毛竹、紫珠、山胡椒、山鸡椒、构树等,主要分布在海拔580和700 m处。2017和2020年海拔580、700和800 m的群落中重要值最大的树种不变,分别为杉木、臭椿和枫香树,而海拔480 m群落重要值最大的树种由杉木变为油茶。各海拔群落径阶分布变化明显。海拔480 m群落径阶分布由倒“J”型发展为单峰左偏态,海拔700 m群落径阶结构由倒“J”型发展为指数型,海拔800 m群落径级分布呈正态分布,峰值由24 cm移到30 cm。3年间各植物群落的Simpson优势度指数和Shannon多样性指数提高,均随海拔升高而显著下降。群落β多样性随海拔升高、海拔间距的增加而增大。2020年新增物种为群落天然更新提供了充足的幼苗幼树,但仍未演替到亚热带顶极群落。

Structure dynamics of communities after cutting Phyllostachys edulis along altitude in Mount Tianmu,China.

We examined the dynamics of community structure in forests formed after cutting all Phyllostachys edulis at altitude of 480, 580, 700 and 800 m of the Mount Tianmu National Nature Reserve in Zhejiang Province, from 2017 to 2020, using phytocommunity method. Results showed that the total number of plant individuals was 515 belonging to 50 species, 43 genera and 27 families in 2017. After three years, 30 new plant species emerged, belonging to 23 genera and 14 families, and the number of individuals increased by 116.9% in 2020. The new species were mainly P. edulis, Callicarpa bodinieri, Lindera glauca, Litsea cubeba and Broussonetia papyrifera, which primarily distributed at the altitude of 580 and 700 m. The tree species with the largest importance value in the communities at altitude of 580, 700 and 800 m remained stable, including Cunninghamia lanceolata, Ailanthus altis-sima and Liquidambar formosana, whereas that in community at altitude of 480 m changed from C. lanceolata to Camellia oleifera. Meanwhile, the diameter distributions of community significantly differed across different altitudes. The diameter distribution of the community at altitude of 480 m displayed a single peak left skewness from the reverse ‘J' type, whilst that at altitude of 700 m developed from a reverse ‘J' type to an exponential type. The diameter distribution in the community at altitude of 800 m followed a normal pattern and the peak value shifted from 24 to 30 cm. Both the Simpson dominance index and Shannon diversity index of the four communities increased across the three years, and all decreased significantly with the increase of altitude. Meanwhile, β diversity increased with rising altitude and increasing distance among altitudes. The recruitment of new species in 2020 provided sufficient seedlings and saplings for natural regeneration, but it had not yet succeeded to the subtropical climax community.