Assessment of hygroclimatic conditions of vegetation in Poland

Natural Environment Monitoring 2013, No 14, 103-111


Krzysztof M. Kożuchowski


The paper presents the evaluation of the radiant index of aridity for Poland’s climate. This index is defined as the ratio of annual value of the long- and shortwave net radiation of the active surface (Rn) to the heat energy required to vaporization of the annual precipitation total: RIA=Rn/LP, where L is vaporization heat (2.48 MJ/kg), P – precipitation total (mm) (Budyko 1975).
It has been assumed that average annual precipitation throughout Polish lowlands (<300 m a.s.l.) equals 592 mm, net radiation equals 1344 MJ/m2 year, and thus RIA = 0.92 (Tab. 1).
Forest ecosystems are to be found in climates where 1/3 <RIA <1. Values 1<RIA<2 correspond to steppes. The maximum of the primary net production corresponds to the index of aridity RIA = 0.8. Assuming the optimum of index for vegetation (0.8) the most favorable sum of the annual precipitation in Poland has been estimated as Popt. = 677 mm. The average actual precipitation is therefore 13% lower than the favorable one. The greatest deficits of precipitation (-20% of the optimum) occur in central and central-east parts of Poland. Precipitation exceeding the preferred values occurs in highlands and partly at the coast of the Baltic sea (Fig. 3). The critical value of precipitation (Pcr) has been estimated as corresponding to the aridity index RIA=1.0. In a number of places in central parts of Poland (Wielkopolska, Kujawy, Mazovia) the average annual precipitation P<Pcr has been identified.
Annual biomass (B) and wood matter (G) production in natural wood subregions in Poland are correlated with the precipitation totals (Pa) and the indexes of climate aridity (RIA) (Tab. 3).