ASSESSMENT OF THE CLIMATE CHANGES IMPACT ON THE PRODUCTIVITY OF MAIZE WITHIN THE POLISSYA AND FOREST STEPPE ECOREGIONS WITHIN UKRAINE

This paper investigates the impact of climate variability on maize yield in the Polissya and Forest- steppe zones of Ukraine. Precipitation and temperature were used as proxies for climate variability. The principal components analysis applied to the bioclimatic variables allowed us to identify four principal components that together account for 92,5% of the variability of the feature space. Principal component 1 describes 54,45% of the total dispersion. It is correlated with the majority of variables, but most with indicators that determine continental climate. Principal component 2 describes 23.78% of climatic variation and can be interpreted as temperature variability in extreme periods of the year. Principal component 3 describes 8,18% of the total variability of the feature space and indicates the degree of variability of the temperature regime. Principal component 4 describes 6,03% of the climatic variability and indicates the contrast of temperature conditions. Maize yield dynamic is best described by a logistic model that has the following characteristic points and indices: slope, lower limit, upper limit, and ED50 – the time it takes to achieve half of the maximum yield level. The regression analysis revealed a statistically significant correlation between maize yield and identified principal components. Thus, the lower yield limit (minimal yield) is determined by the principal component 1. The rate of recovery of yield potential depends on all four climate variables, but it has the greatest sensitivity to the principal component 1. Climate component 3 is the determinant of the upper maize yield limit, which indicates that the maximum maize yield is limited by the temperature regime of the territory. The time of a sharp increase in yield also depends on the variability of the temperature regime