Considering that the soil-plant relationship is very important for understanding the development of planted forests and natural forests, the aim of this study was to quantify the accumulated litter and organic carbon in a Pinus elliotti Engelm plantation (33 years old) and a Montane Ombrophilous Mixed Forest (FOMM) in Irati, PR. The Montane Mixed Ombrophilous Forest revealed a high potential for accumulating litter and fixing carbon when compared to other tropical forests, and the same finding was observed in the Pinus elliottii plantation, recommending periodic monitoring of the stocks of biomass and carbon accumulated in these forest formations.