RESTORATION OF SPECIES-DIVERSITY IN GRASSLANDS - THE EFFECT OF GRASSLAND MANAGEMENT AND CHANGES IN-GROUND WATER-LEVEL

Results are presented of a grassland restoration experiment on a humic sandy soil and on a nutrient rich humic clay. The effect of cutting t ime and frequency, sod stripping and a rise in ground water level is s tudied on the decrease in dry matter and nutrient yield and changes in botanical composition. When the annual production is lower than 6 ton nes a second cut hardly contributes to a faster soil impoverishment. B ut a second cut creates a favourable vegetation structure for seedling establishment. Sod stripping to 5 cm caused only for a short period a lower production, but it stimulates the establishment of species from the soil seedbank. The yield of N and P is lower in the longer run, t hat oi K is very low with and without scd stripping. The changes in yi eld and concentration of K in the biomass show that the availability o f K is very low and possibly limits the further decrease in the dry ma tter production. Establishment and generative spread of plant species in the undisturbed sward are low, but can be stimulated by cutting aft er their seed production. Rising the ground water level in a productiv e system hardly lowers the production on the short term, but it stimul ates the replacement by species indicative for wet growing conditions. The results show that alter the first phase of restoration management , which is aimed at a decrease in production, other factors become lim iting for the increase in diversity: presence of seeds, favourable con ditions for seedling establishment and co-limitation of nutrients.