Use of agricultural conservation practices such as slash-and-mulch, as an alternative
to slash-and-burn, is less harmful to biogeochemical cycling and helps to mitigate climate change. The aim of this study was to estimate soil carbon emission and
stocks in smallholder agricultural units in Northeast of Pará. The study was carried
out in the municipality of Mãe do Rio. Average annual temperature in this area varied
from 25 to 28 °C and rainfall typically is higher than 2500 mm; predominant soil is
Yellow Dystrophic Oxisol with texture varying from medium to clayey. In this
research, we selected three land use systems (Schizolobium amazonicum plantation,
Manihot esculenta crop, and silvopastoral), which were compared with a reference
area (regrowth forest); we established four 20 m x 20 m plots in each system. We
measured monthly soil CO2 efflux as well as soil carbon stock and aboveground litter
carbon stock. Analysis of variance was used to test the effects of land use systems
and regrowth forest effects on carbon emission and stock; Tukey test at 5% was
used to compare treatment means. The silvopastoral system showed the highest
monthly soil CO2 emissions, which were observed during the rainy season; this
system also had the largest annual emission. Soil carbon stock was significantly
higher in the regrowth forest was 157 ± 31,10 Mg ha-1 (0-100 cm). Litter stock was
higher for the non-woody fraction than the woody fraction for both land use and
regrowth forest systems. The largest stock of carbon in non-woody litter (overall
mean = 4.31 ± 3,0 Mg ha-1) was observed in January 2010. Our results suggest that
the land use systems that do not use fire in land preparation, such as the slash-andmulch
system, helped to maintain carbon biogeochemical cycling.
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