Liming and N, P addition in a grassland dominated by Cyperaceae species in the plateau of Ioannina

The aim of this work was to examine how the liming and the soil enrichment with N and P influence the above-ground vegetation and the species composition in grassland areas dominated by species of Cyperaceae and having low soil pH values. In a grassland, characterised by low soil pH and the dominance of the Cyperaceae species Carex hirta and Cyperus longus, the effects of liming (0 and 800 g/m2, applied once at the beginning of the experiment) and the N (0 and 15 g/m2 per year) and P (0 and 4.5 g/m2 per year) enrichment were examined on vegetation production for four years. Liming did not affect the total aboveground vegetation nor the species composition, although it increased the soil pH. Addition of N increased the total aboveground vegetation 13% (averaged means over the four years). This increase was due to the significant increases at the first three years of the Cyperaceae species Carex hirta and of the annual grasses Alopecurus urticulatus and Bromus hordeaceus and decreased the other forbs. Addition of P affected significantly by increasing only the total legumes. Between years, the total above-ground vegetation was the highest in 1992 because of the relatively high temperatures of the preceding winter and the uniformly distributed rainfall during the spring. Addition of N affected significantly the species composition by progressively increasing the relative abundance of the annual grass Alopecurus urticulatus and the forb Galium aparine and progressively decreasing that of Cyperus longus and of forb Plantago lanceolata. The dominant species Carex hirta was progressively increased but the forb Rorippa sylvestris was decreased.