AGROCLIMATIC TERMS OF ND FORMING OF THE PRODUCTIVITY OF PRATAL AND STEPPE VEGETATION IN THE CONDITIONS OF CHANGE IN NORTH STEPPE OF UKRAINE

Abstract

Impact of climate change on the agro climatic conditions of growth, development and productivity of grassland and steppe vegetation in the Ukrainian Steppe is studied for three periods of 2021–2030 years, 2031–2040 years, 2041–2050 years by comparing the multiannual means for the 1961-1990 period. The expected conditions in three periods are calculated under the RCP4.5 and RCP8.5 scenarios. Three categories of the productivity of grasses, namely potential yield, meteorologically possible yield, practically possible yield, and conditions of forming of leaf surface, rate of photosynthesis and photosynthetic potential, are considered. Under the mean multiannual agricultural meteorology conditions, the potential yield of all dry matter in grass is 385 center/ha. Calculations based on scenarios show, that during two first appraisal periods potential yields will amount to 124–127% from the multiannual mean, and for the third calculation period potential yield will amount to 108% from the multiannual mean. Dry matter in meteorologically possible yield in the first period under both scenarios will be expected at the level of 130–136% of the multiannual mean, relatively fewer one will be expected in the second and third appraisal periods – within the limits of 123–130% from the multiannual mean. The practically possible yield of dry matter in plants, stipulated by natural fertility of soil, will amount to 138% from the multiannual mean in the first period, in the second and third periods such yield will be 123–131%. It is found that under the multiannual mean conditions yield of above-ground mass in steppe vegetation under the standard humidity of 16% is 1,3 t/ha. In scenario periods the potential yields will be expected at the level of 120–123% from the multiannual mean. Calculations showed that under the climate change in the case of realization of scenarios of RCP4.5 and RCP8.5 the increase of humus balance is assumed in all three appraisal periods. In the first period the increase will reach 136% from the multiannual mean, in the second and third ones the increase will be to 125–130%.