浅水湖泊孢粉和植物残体对水生植被的表现率

REPRESENTATION OF AQUATIC VEGETATION BY MACROFOSSIL REMAINS IN A SHALLOW LAKE

研究浅水湖泊中植物残体对水生植物的表现率,用于重建近代水生植被历史,可为治理湖泊富营养化,恢复湖泊生态环境提供依据。研究选址为英国北部的一个小湖泊,通过水生植物调查及表层沉积物中植物残体和孢粉分析,及地理信息系统方法定量研究植物残体对水生植物的表现率。结果表明:沉积物中植物残体精确地反映了植物优势种的存在;植物和植物残体的关系是很复杂的,有些植物在残体中表现率明显超高,而有些表现率偏低;应把叶子和其它非繁殖植株部分作为恢复近代多年生植物历史依据;植物残体传输性较差,主要集中在植物母体附近;利用植物残体与孢粉分析相结合的方法能更准确地重建植被历史。

The research aims to study the representation of aquatic vegetation by macrofossil remains in shallow lake and hence to provide a contribution of the quantitative research of plant macrofossil analysis on production, transportation and deposition, which in turn will provide a much more robust palaeo-botan- ical tool that can be applied to issues of major nature conservation importance. The study site is Green Plantation Pond in N Norfolk, UK. Detailed aquatic plant surveys were carried out and surface sediment samples were collected. These samples were analysed for plant remains (all 30 samples), and aquatic pol- len (4 samples). All data were stored as separate layers in a Geographical Information System. The rela- tionship between the aquatic vegetation and plant remains was quantitatively analysed. The results showed that the macrofossils accurately recorded the dominant macrophyte species in the lake, such asChara, PotamogetonandElodea.Relationships between macrophytes and their sedimentary remains were com- plex. Some species were significantly over-represented by the macrofossils (e.g.Charaspp.,Nitella mu- cronataandZannichellia palustris ), while others were under-represented (e. g.Potamogetonspp.). In contrast to the pollen assemblages, plant macrofossils were not evenly dispersed into all parts of the lake, with higher concentrations of remains (particularly for thePotamogetonspecies) being found close to areas of source-plant dominance. The importance of searching for leaf and other vegetative fossils as a means of determining the past presence of perennial plants such asPotamogetonis emphasised in this study. Most of the taxa which are very important in the vegetation are reflected reasonably faithfully by the combination of pollen and macrofossil.