The Atlantic Rainforest is currently considered as biome conservation priority, given its
history of devastation, closely related to the history of Brazil's development since its
discovery. The small forest fragments remaining, totaling around 7% of the original forest
cover resulted in actions that prioritize the conservation of these forests and the enforcement
of laws governing man's actions regarding the appropriate alternate use of the soil and natural
resources in a general way. Among the numerous environmental services that forests can
generate, carbon accumulation in the forest biomass has significant importance for the ability
to sequester carbon from the atmosphere, resulting in minimizing the high concentration of
Greenhouse Effect Gases. The emergence of global policies, discussing the issue of mitigating
the causes of climatic change, has resulted in the design of easing measures, which the main is
Clean Development Mechanism (CDM) provided in Kyoto Protocol. The planting of forest
trees for fixing CO2 from the atmosphere may propose models for generating carbon credits
and be an alternate recovering of degraded areas, conservationist use of the soil and reconnect
forest fragments. The aim of this study was to characterize the floristic composition, quantify
the carbon stock in biomass above the ground and the carbon stored in the soil, as well as
other compartments of the terrestrial ecosystem as litter and root systems in areas of
reforestation of different ages in Guapiaçu River in the city of Cachoeiras de Macacu, RJ,
Brazil. Three areas of reforestation plantations were evaluated with different ages: 3 years, 5
years and 7 years. In Chapters I and II, mature forest remaining of the city where the study
was conducted were used as a control area for comparisons of floristic parameters,
phytosociological, quantification of biomass above the ground, root and leaf litter and
estimates of the carbon stored in these biomasses. The non-destructive method to evaluate the
biomass above the ground was effective both in natural forest areas, and reforestation area.
However, it is adviseable to use the destructive method to evaluate the reliability of the data
obtained for reforestation. In Chapter III, the pasture was used as a control area for
comparison purposes between the carbon stocks in the soil biomass and to evaluate the origin
of carbon and nitrogen in the organic matter of the soil through the natural abundance of the
isotopes 13C and 15N. The use of an alternate method allowed to evaluate the consistency of
the results of carbon stock, which allowed suggesting the inclusion of this compartment of the
terrestrial ecosystem in the forest projects of CDM. It is concluded that reforestation aiming at
ecological restoration are important sources of atmospheric carbon capture and may present
significant results, where the studies quantifying the biomass and carbon stocks estimates in
the soil and air compartments of the reforested areas can be used as refere
