Effects of flooding and trampling on the performance of river foreland species of Rumex and Plantago

The effects of a combined regime of flooding and trampling on survival, growth and reproduction of some species from river forelands, were studied in a large-scale, outdoor experiment. In additional pot experiments, trampling effects were separated into effects of shoot damage and of soil compaction. Resistance of individual leaves to a tearing force and recovery from damage were measured. Species were selected according to their occurrence in the field in relation to trampling and flooding: Rumex acetosa from seldom flooded, extensively trampled sites; R. crispus from frequently flooded, non-trampled sites; Plantago major ssp. pleiosperma from regularly flooded, non- to heavily-trampled sites and P. major ssp. major from seldom flooded, very heavily trampled sites. Only R. crispus showed obvious morphological adaptations to flooding but their significance was vastly reduced when flooding was combined with trampling. Although they did not possess any important morphological adaptations, both Plantago subspecies survived flooding. Of both Plantago subspecies, P. major ssp. pleiosperma performed better than P. major ssp. major when soil compaction resulted in hypoxia. P. major ssp. major. responded better when the major effect was an increase in penetrometer value. R acetosa was negatively affected by trampling, flooding and the combination of both. Flooding inhibited flowering during the experiment and trampling reduced seed production. In the pot experiment no interaction was found between shoot damaging and soil compaction due to trampling. Responses to shoot trampling could largely be explained by the tearing resistance in combination with the recovery characteristics of the species. Species occurring on more trampled sites in the field had a higher resistance to tearing stress and a better recovery after shoot damage.