Atlantic Forest is one of the most threatened biome in the world. Despite of its richness in
terms of biodiversity it occupies only 11-16% of the original area and appears as a mosaic of
fragments in the landscape. At Rio de Janeiro State and especially in Middle Valley of
Paraíba do Sul River, the forest (and landscape) degradation was favored by several crop
cycles and relief, extremely hilly. Today the fragments in the region are immerged mainly in
pasture matrix with a low capacity support. The knowledge of biogeochemistry cycles in
these important landscape components is scarce and could contribute for a biological
conservation programs. In this direction, this study was carried out to characterize the
structure of tree fragment in different successional stages (initial - IS, intermediary – INS and
advanced stages, AS) and those carbon and nutrient compartments and fluxes. Above and
below ground (fine roots: <2 mm) biomass and carbon accumulation were estimated using
allometric equations and monolith method, respectively. Natural abundance of 13C was used
to evaluate the dynamic of soil organic matter. The contribution of rainfall and forest for
nutrient cycling inside the fragment was accessed by a biweekly sampling program. Fifteen
pluviometers and ten stemflow collectors were installed at the breast height of selected trees
to represent each fragment and compartment. All those compartments were monitored for 1
year, but the sampling frequency was weekly. An addition study was developed using
geographic information system to evaluate the expansion of those fragment over a 30 years
chronosequence. The AS fragment presents the highest richness (thirty four botanic families),
aboveground biomass (one hundred seventy one Mg ha-1) a tendency to stock more carbon
and nutrients in this compartments. Fine roots were concentrated in the superficial soil layer
(0-10cm) for all fragments and season (3,08 Mg ha-1 dry and 2,51 Mg ha-1 wet), but highest
values were detected to AS fragment. Despite of this biomass the CO2 soil efflux was higher
to INS fragment (16,0 Mg ha-1) in comparison to AS (13,5 Mg ha-1) and IS ( 15,5 Mg ha-1)
fragment. Areas of AS and INS had showed an increase of δ 13C values in the 0-10 cm layer
in relation to the layer of 10-20 cm, from (-27.2 ‰ to -26.5 ‰) and in AS -26.5 ‰ to -25.2 ‰
in INS and the values of δ 13C stabilize from 60 cm deep. This is an indication that the
progress of regeneration of forest areas are already reflected in soil carbon. Therefore arrive
at the conclusion that despite of fragmented landscape of Middle Valley of Paraíba do Sul
River, the ecological memory of Atlantic Forest in the region, associated to decline in cattle
management contributed to an increase of fragments area.
