HUMIC ACIDS OPTICAL PROPERTIES OF RENDZINA SOILS IN DIVERSE ENVIRONMENTAL CONDITIONS OF SERBIA

This study examined the impact of climate, altitude and landforms on humic acids (HA) opticalproperties (E4/E6, ΔlogK, RF indexes) in Serbian Rendzina soils. HA humification degree of calcareousand decarbonated Rendzinas under natural vegetation (forest and grassland, separately) decreased withaltitude increasing. This particular rule was not manifested in arable Rendzinas. HA humificationdegree in Rendzinas on flat positions (hilltop and footslope) is significantly higher than in Rendzinas onslope sides. Humification degree of HA is the highest in Rendzinas in eastern Serbia (in the vicinity ofNegotin), followed by central Serbia (Sumadija) and Srem, southeast and finally, southeast andsouthwest Serbia. With respect to the climate change foreseen for the end of this century, i.e. increase ofprecipitation and temperature variance among the regions in Serbia, also an increase in variance ofquality of humic acids in Rendzinas on different altitudes and regions can be expected