This study quantify the total organic carbon content, light fraction organic matter (LFOM), and soil organic matter fractions (from chemical and physical fractionations) in four different cultivation areas: 1 and 2) rubber tree clonal plantations (FX 3864 and IAN 873); 3) a pasture; and 4) a secondary forest. The research was carried out using soil samples from clonal plantations of eight-year-old rubber trees, located in the coastal plain (Tabuleiros Costeiros) of the state of Rio de Janeiro. The difference in the management of the rubber tree clone area promoted improvements in the soil quality, as it increased the carbon contents of the granulometric fractions, LFOM, and humic substances from the IAN 873 clone area. Both rubber tree areas evaluated presented higher mineral-associated organic carbon levels and humic substances than did the pasture area, reinforcing the reforestation potential of areas with degraded pastures through hevea culture.
