APPLICATION OF THE BRITISH NATIONAL VEGETATION CLASSIFICATION TO THE COMMUNITIES OF THE PARK GRASS EXPERIMENT THROUGH TIME

The Park Grass Experiment at Rothamsted consists of a series of fertil izer treatments which have been applied to a species-rich hay meadow a nnually since 1856. Detailed botanical analyses of the plots between 1 862 and 1992 were classified to one of the National Vegetation Classif ication (NVC) communities using the similarity measured by Czekanowski coefficient using computer program MATCH. Results indicated that ''co ntrol'' unfertilized plots were a relatively stable Cynosurus cristatu s-Centaurea nigra dicotyledon-rich grassland. However mineral fertiliz ed plots moved towards a species-rich Arrhenatherum elatius grassland MG1e after 50-80 years and remained there. Plots receiving nitrogen fe rtilizer moved first to MG1e then on to a Lolium perenne-Alopecurus pr atensis grassland MG7D. Perhaps the most interesting plot was one whic h received a low rate of the soil acidifying ammonium sulphate fertili zer; the species composition changed towards a MG7D (Lolium perenne-Al opecurus pratensis) community between 1856 and 1903 but since then a l iming treatment has been applied to part of the plot and the species c omposition on that part has recovered to a MG5 community resembling th e control plots, taking 70-90 years to do so.