Abstract

Humic and fulvic acids (HA and FA) extracted from tropical forest soils (at 150 and 750 m altitude, under lowland west coast and west coast tropical evergreen forest, respectively) and a subtropical forest soil (at 1450 m altitude, under southern tropical broadleaved hill forest) in Kerala, were characterized by elemental analyses, and UV and IR spectroscopy. HA, FA, C and N contents were higher in the subtropical forest soil. They did not increase in exact proportion to the organic matter contents. Aliphatic groups were lower in HA of tropical soils while their FAs were poorly aromatic. These changes may be due to the differences in clay and moisture contents and vegetative cover