Changes in foliar nutrient content and resorption in Fraxinus excelsior L., Ulmus minor Mill. and Clematis vitalba L. after prevention of floods

This paper focuses on the impact of flood on tree mineral nutrition through measurement of resorption (i.e. transfer of nutrients from leaves to peren nial organs). Nutrient (N, P, K, Mg, Ca) concentrations in leaves of three representative species, Fraxinus excelsior L., Ulmus minor Mill. and Clemat is vitalba L. were measured before and after abscission on flooded and unfl ooded hardwood forests of the upper Rhine plain. The nutrient concentration s in the soils, which were measured in the top layer of the study sites, we re higher in the flooded sites for P but slightly lower for N and K, and id entical at both types of site for Ca and Mg. The summer foliage concentrati ons were higher for N and P in the flooded areas, and probably related to t he flooding process, which contributes to regular nutrient inputs in the fl ooded forest, causes high fluctuations of water level and increases bioavai lability of certain nutrients. Resorption occurred for all nutrients in the three species, and was higher for N, P and K (40-70 %) than for Ca and Mg (0-45 %), but not significantly different at the two sites. This paper stre sses the variability of the test species response (nutrient content and res orption) to the soil and flood water nutrient sources, and tries to specify parameters which control resorption, i.e. soil fertility, tree species or flood stress. (C) 1999 Inra/Editions scientifiques et medicales Elsevier SA S.