Ecological studies on Potamogeton pectinatus L. IV. Nutritional ecology, field observations

Abstract

The chemical characteristics of the plant parts and habitats of several populations of Potamogeton pectinatus L. in The Netherlands and France (Camargue) were studied. In the natural habitat P. pectinatus occurs in a broad range of ion concentrations, compared with that of aquatic macrophyte habitats in general. Cluster analysis of the chemical composition of water and interstitial water showed a division in a relatively large and a smaller group of observations in both cases. Cluster analysis of the plant parts also indicated two main groups. The roots and shoots of the larger group were chemically characterized by their low phosphorus and sodium contents. The reproductive parts (achenes and tubers) mostly showed low sodium, magnesium and potassium contents. Achenes were additionally characterized by low phosphorus and nitrogen contents. In general, both cluster and correlation analyses of the chemical data indicated a relationship between ambient water, pore water and the roots and shoots of P. pectinatus. The chemical composition of the reproductive parts, achenes and tubers, was more independent of the chemical environment, compared with the other plant parts. It is concluded that cluster analysis can be very useful to analyse complex ecological data sets and to identify structural, functional and environmental units.