A METHOD FOR CLASSIFYING EUROPEAN RIVERINE WETLAND ECOSYSTEMS USING FUNCTIONAL VEGETATION GROUPS

1. The aim of this work is to formulate a methodology for the use of trait analysis to classify European riverine wetlands into functional vegetation types. Plant species and data on biological traits and survival strategy were collected from sites in England (Bradford Mill and Kismeldon, River Torridge), France (R. Allier at Apremont and the R. Loire at Decize) and Ireland (R. Shannon at Clonmacnoise and the Little Brosna near Banagher) during 1991. 2. Linear and multiple discriminant analyses were used to distinguish objectively between plant populations with a priori-selected strategies. There appeared to be very little variation in disturbance-tolerance (D) between the wetland plant populations studied. Competitive and stress-tolerant plants were found to be significantly different by linear discriminant analysis using 12 descriptive parameters. Multiple discriminant analysis permitted a distinction to be drawn between competitive (C), stress-tolerant (S) and intermediate strategy plants, and retrospectively classified the populations in accordance with the strategies suggested for them by previous work . 3. Stepwise multiple regression was used to identify the important survival traits for predicting competitive ability and stress tolerance. Significant predictors of the C strategy were the height of the plant and the dry weight of the leaves; and of the S strategy the dry weight of stems and weight per seed. Use of the predictive equations permitted the importance of the C and S strategy elements to be determined for 78 plant populations. 4. Weighted for plant cover, mean C and S scores of the plant populations present in each sample unit of vegetation were utilized to determine the functional vegetation type (FVT) in terms of competitiveness (CFVT) and stress tolerance (SFVT). Vegetation samples were ordinated using CFVT and SFVT values. CFVT and SFVT values were highly inversely correlated: a trade-off between competitive ability and stress tolerance in wetland plants was apparent.