三峡库区不同消落带下中华蚊母树群落特征及其与土壤环境因子的关系

中华蚊母树(Distylium chinense)是华中地区特有种, 在三峡库区局部地段占优势形成群落。对三峡库区不同生境下中华蚊母树群落特征及其与土壤环境因子的关系进行研究可为其保护及消落带植被恢复提供科学依据。运用数据分类和排序等方法, 对中华蚊母树群落物种组成、植物区系、物种多样性及其与土壤环境因子的关系进行研究。结果表明, 共发现维管植物56种, 隶属于36科54属, 植物区系以世界分布、泛热带分布和北温带分布为主, 生活型以草本和灌木为主。自然消落带灌木层重要值最大的是中华蚊母树, 草本层重要值最大的是藤本植物地果(Ficus tikoua), 主要伴生种为具有一定水淹耐受性的灌木和多年生草本, 如小梾木(Swida paucinervis)、白茅(Imperata cylindrica)等; 反季节消落带灌木层仅中华蚊母树一种, 草本层重要值最大的物种是狗牙根(Cynodon dactylon), 主要伴生种为苍耳(Xanthium sibiricum)、苘麻(Abutilon theophrastic)等一年生草本。双向聚类分析将调查的6个样地分为四大类群: 中华蚊母树+小梾木群落、中华蚊母树+地果群落、中华蚊母树+细叶水团花(Adina rubella)群落、中华蚊母树+狗牙根群落。典范对应分析表明, 海拔高度和土壤pH是影响中华蚊母树群落物种分布的主要环境因子, 土壤有机质、全氮、全磷和速效钾含量是次要因素, 但它们是影响群落物种多样性指数的主要因子, 其中土壤氮是群落的限制因子。因此, 在反季节消落带植被重建中, 对中华蚊母树群落进行构建时, 除考虑细叶水团花、小梾木等作为高海拔消落带伴生物种外, 还应增加土壤氮和钾的供给, 使中华蚊母树群落保持较高的物种多样性, 维持消落带生态系统稳定。

Characteristics of Distylium chinense communities and their relationships with soil environmental factors in different water level fluctuation zones of the Three Gorges Reservoir,China

Aims Distylium chinense is endemic to central China, and can be dominant species in parts of the Three Gorges Reservoir area. Studying the characteristics of D. chinense communities and their relationships with soil environmental factors under different habitat conditions could help gain knowledge assisting the community protection and vegetation restoration in the water level fluctuation zone of the Three Gorges Reservoir. Methods Measurements were made on species composition, floristic characteristics, and plant diversity in D. chinense communities in 24 plots (4 m × 4 m) covering six study sites across the water level fluctuation zone of the Three Gorges Reservoir. The relationships of varying community traits with soil environmental factors were determined by quantitative classification and ordination methods. Important findings A total of 56 plant species were recorded across the 24 sampling plots, belonging to 36 families and 54 genera. The plant communities mainly composed of the cosmopolitan species, pantropical and north temperate of D. chinense community, predominantly as herbs and shrubs. In the natural water level fluctuation zone, D. chinense scored the highest importance value in the shrub layer, and Ficus tikoua in the herb layer. The companion species of D. chinense commumities were shrubs and perennial herbs with flooding tolerance, such as Swida paucinervis, F. tikoua, Imperata cylindrica, etc. However, in the off-season water level fluctuation zone, D. chinense was the only plant in the shrub layer, with dominance of Cynodon dactylon in the herb layer and other companion species as annual herbs, such as Xanthium sibiricum, Abutilon theophrasti, etc. Two-way cluster analysis divided the six sites into four community types: D. chinense + S. paucinervis, D. chinense + F. tikoua, D. chinense + Adina rubella, and D. chinense + C. dactylon. Canonical correspondence analyses showed that altitude and soil pH were the main environmental factors affecting the species distribution of D. chinense community, followed by the content of soil organic matter, total phosphorus, total nitrogen, and available potassium, which were the main influencing factors of species diversity index with nitrogen being the limiting factor. In rehabilitation of the off-season water level fluctuation zones of the Three Gorges Reservoir, small shrubs such as A. rubella and S. paucinervis should be used as the companion species of the upper slopes with increased supply of soil nitrogen and potassium, in order to promote higher species diversity of the D. chinense community and to maintain the stability of water level fluctuation zone ecosystems.