FERTILIZATION AND IRRIGATION EFFECTS ON THE GERANIUM-HEDYSARUM MEADOWS, NORTHWESTERN CAUCASUS, RUSSIA
We investigated the response of alpine highly productive plant community to soil nutrient addition and irrigation. A 10 year experiment - including additions of calcium, phosphorus, nitrogen, phosphorus + nitrogen and irrigation - was conducted in northwestern Caucasus, Russia, at 2800 m above sea level. We found out that above-ground biomass did not change significantly. But the biomass increased by 25% in case of the treatment with calcium addition compared with the control, also the floristic richness in this treatment was not changed. Biomass of the main dominant Geranium gymnocaulon doubled in Ca and NP. Campanula tridentata, Carum meifolium, Euphrasia ossica and Matricaria caucasica increased in Ca; Geranium gymnocaulon in Са and NP; Gagea fistulosa in NP; Agrostis vinealis in N and NP; Carex atrata, Nardus stricta in N; Phleum alpinum in Р; Leontodon hispidus in irrigation treatment. Above-ground biomass of separate species was changed due to the number or mass of shoots changing. Biomass of Geranium gymnocaulon was changed mainly due to the mass of shoots changing, and on the contrary Hedysarum caucasicum - due to the shoot number changing. Sedges had a positive response to N. Legumes had a negative response to NP, N and Ca.