Stocks of carbon and nitrogen and distribution of humic substances under different forest covers

Abstract

To evaluate organic carbon (C) and nitrogen (N) stocks and humic substances distribution (fulvic acid (FA), humic acid (HA) and humin (HUM)) soil  samples were collected in the 0-5, 5-10, 10-20 and 20-40 cm depths in areas of Mimosa caesalpinaeolia, Carapa guianenses and secondary forest in FLONA Mário Xavier, Seropédica (RJ). The secondary forest area presented the highest C and N stock values. As for the humic fractions distribution, in all areas the prevalence of HUM fraction was observed. The highest values of AF, AH and HUM fractions occured in the secondary forest area. The highes contents of C and N stock and the humic substances content in the secondary forest area may be in function of the higher clay content verified in this area. As for distribution of humic frations in all areas HUM was found to be predominant.