Zmienność higroklimatycznych warunków wegetacji roślinności leśnej w Polsce w latach 1951–2015

This work presents assessment of changes in hygroclimatic conditions determining the vegetation and productivity of forest area. Selected indices such as radiant index of climate aridity – RIA, optimal precipitation – Popt, critical value of precipitation – Pkrt and CVP index (Climate, Vegetation, Productivity), which described annual biomass and wood matter production under climatic conditions, were used. The analysis is based on standard meteorological measurements taken from 21 stations from the period 1951–2015. The daily data were employed to calculate mentioned earlier indices, next linear trend coefficient were used as an assessment of hygroclimatic conditions changes. The results show an increasing tendency in dry climate conditions (positive values of RIA linear trend coefficient) in the large part area contain: Wielkopolska and Silesian lowlands, and southern Poland. These areas are also characterized by the fastest increase in the most favourable sum of precipitation Popt and critical precipitation Pkrt for forest vegetation. This means deterioration of water resources in the environment and hygroclimatic conditions important for vegetation and productivity of forest vegetation. On the other hand, the results of CVP change assessment show the improvement of climatic conditions influencing vegetation and forest productivity. The greatest positive changes of CVP index are in the areas of south-eastern Poland.