FOLIAR MACRONUTRIENT CONCENTRATIONS OF FOREST UNDERSTOREY SPECIES IN RELATION TO ELLENBERGS INDEXES AND POTENTIAL RELATIVE GROWTH-RATE

In order to investigate broad patterns of variation of the foliar mine ral nutrient concentrations of herbaceous plant communities in the gro und layer of W Europe forests, correlations were examined between Elle nberg's indices (N-index: mineral nitrogen availability, R-index: pH, F-index: soil moisture and L-index: light intensity) and literature va lues of macronutrient concentrations for 84 forbs and 39 graminoid spe cies. Significant, positive correlations were found between the R-inde x and the plants' concentration of Ca and K (forbs only) and between t he N-index and the plants' concentration of K, P (forbs only) and N (f orbs and graminoids). Multiple regressions showed that the N-index was the best predictor of the plants' concentration of N (forbs and grami noids), P (forbs) and Ca (graminoids) and the R-index of the plants' c oncentration of Ca and K (forbs). The mineral nutrient concentrations of graminoids were lower and less strongly correlated with Ellenberg's indices than those of forbs. It is argued that the mineral nutrient c oncentrations in the plants match the availability of mineral nutrient s in the soil for N, P (N-index) and Ca (R-index), but not for K and M g. Significant, positive correlations were found between potential rel ative growth rate and the concentration of some elements (N, P, K and Ca in forbs, Ca and Mg in graminoids). This suggests that the increase in the concentration of these elements in plants along fertility grad ients is due, at least partly, to genetically controlled alterations o f leaf anatomy associated with increasing potential relative growth ra te.