LONG-TERM DYNAMICS OF STANDING CROP AND SPECIES COMPOSITION AFTER THE CESSATION OF FERTILIZER APPLICATION TO MOWN GRASSLAND

(1) Current agricultural overproduction in Western Europe has led to an increase in the area of unfertilized grassland. This paper reports an experiment where fertilizer application was stopped to try to restore former species-rich vegetation. (2) Standing crop and species composition of three different fields were studied during the first 14 years after cessation of fertilizer application. In two fields on peaty soil a strong decrease in standing crop (from 800 to 300 g m-2) was observed but in a field on sandy soil, the initial production of 300 g m-2 did not decrease. The deviations from the mean between years were significantly correlated to the potential water surplus in the growing season in this latter field, but not for the two fields on peaty soil. The species composition changed gradually in all fields. (3) In the two fields with decreasing standing crop, species-richness per field and per 4-m2 plot increased markedly during the 14 years. A maximum of forty species was observed after 8 years in the field on sandy soil. (4) Several species reached their maximum cover during these successions. The dynamics of species replacement was described using a Guassian response model for each species. Species indicating nutrient-poor conditions entered earlier in the successional sequence with cutting twice a year and in the field on sandy soil. The results are discussed with regard to diversity-productivity relationships, nutrient cycling and adaptations of species to nutrient-poor conditions.