北固山湿地植物群落特征及其物种多样性研究

北固山湿地位于镇江市东北,由长江携带泥沙长期沉积形成,植被属原生裸地演替,植物种类丰富。但近年由于污染排放及渔民围网捕鱼,植被受到破坏,生态功能被削弱。采用样方法调查了镇江北固山湿地植物群落的组成,种类和外貌,并分析了其物种的多样性差异,从而为湿地的生态修复提供理论和技术依据。试验结果表明:群落物种组成较为丰富,有15科28属33种,但仅限于草本植物,生活型以地面芽植物和一年生植物占优势,物种出现频度上以D、C两个级别为主,表明群落内物种的分布较为均匀。从季相动态上看,季相明显,群落的优势种2~4月前是虉草(Phalarisarundinacea)单优种群,4~6月是虉草-芦苇(Phargnitescommunis)共优种群,6~11月是芦苇-酸模叶蓼(Polygonumlapathifolium)共优种群。随着基底高程的变化,植物呈现明显的平行于堤岸的带状分布,并形成区别明显的三个区域。其中,物种的丰度、多样性指数、群落的均匀度以及生物量均随基底高程的增加而增加,而生态优势度却随基底高程的增加减小。物种多样性指数受立地环境和人为因素的共同影响。其中,一定程度的人为干扰虽降低物种丰度,但由于其对优势种芦苇破坏较为严重,降低了群落的生态优势度而相应提高了群落的均匀度,最终对物种多样性指数有增加效应。在以上研究的基础上,提出了禁止污染排放及围网捕鱼等措施,并在裸露或物种稀少区域人工栽培土著物种以增加湿地生态系统物种的多样性和稳定性。

Characteristics and Species Diversity of Plant Community of the Beigushan Wetland

Wetlands are viewed as "Kidney of the nature" due to their abundant resources and unique ecological structure and functions, but the wetlands in the world are subjected to some serious threats such as reclamation, environmental pollution and over-exploitation of natural resources. In some areas, those threats had resulted in the continuous degradation, even loss of wetlands. Facing such serious situation, a lot of conservation researches were carried out. However, the conditions of degradation in various wetlands were considerably different. The objective of this study was to probe into the conservation and restoration measures of the Beigushan wetlands by studying its plant community characteristics and species diversity. In the Beigushan wetlands, 90 plots were designed and investigated by sampling method. Based on the plot data, plant community characteristics and species diversity were analyzed by species composition, the flora feature, the community physiognomy and so on. The index of the frequency, the coverage, the biomass and the species diversity index, the richness index and the evenness index were measured. The results showed that the species composition of the community was relatively rich , 33 species of plants, belonging to 15 families 28 genera, were recorded, but all confined to herbaceous plant and the structure of community was simple somewhat. The dominate life-form types were Geophytes and Therophytes. The characteristics of the seasonal aspect of community were obvious, Phalaris arundinacea was monodominant species from February to April, Phalaris arundinacea and Phargnites communis were co-dominant species from April to June , Phargnites communis and Polygonum lapathifolium were co-dominant species from June to November. The species richness, species diversity and community evenness and biomass increased with increasing height of the land-base, the ecological dominance was opposition. The species diversity indices varied according to the site conditions and anthropogenic effects. To a certain degree, anthropogenic disturbance decreased the species richness, but it had an increasing effect on the species diversity index by increasing community evenness, which just illuminated species diversity index was a synthetical index of the species richness and evenness. Based on the research results, the strategies of wetland protection were discussed. On one hand, by prohibiting contamination discharge and fishing action by mowing Phargnites communis and enclosing some areas with nets to reduce anthropogenic excessive disturbances. On the other hand, by cultivating native high-stem herbaceous species which belong to plant community of late succession period and some tolerance-water shrub and tree species in naked or rare-species areas to increase the species diversity and maintain wetland ecosystem stability.