Efeitos da exclusão da chuva no fluxo de CO2 do solo na floresta nacional de Caxiuanã, Pará.

Abstract

An experimental of field was conducted in the National Forest of Caxiuanã, Pará, Brazil, (1°43'35'' S; 51°27'36'' W), with the objective of investigating the effect of drought on the forest cycle and the alterations caused by the event. Two plots (A and B) of 1 hectare each, were used, one as reference (control plot) and the other (exclusion plot) where the experiments were carried out with the exclusion of approximately 70% of the rainfall. The analyses presented in this study refer to information obtained for November, 2004 and November, 2005. The average soil respiration was higher in the wet season in both plots, 3.49 μmol CO2 m-2 s-1 and 3.88 μmol CO2 m-2 s-1, respectively, and lower in the dry season, 3.41 μmol CO2 m-2 s-1 and 2.44 μmol CO2 m-2 s-1, respectively. The average soil humidity was 12.3% and 9.0% in plots A and B, respectively. The average soil temperature in the period studied for plots A and B were 25.9±1.2 ºC and 25.8±0.8 ºC, respectively. One better correlation of the precipitation accumulated in 3 days before the reading with the CO2 efflux of the ground was found (R = 43.6%). It was found a better correlation between the rainfall of the 3 days period before starting measurements and the soil CO2 efflux (R=43.6%). The correlations between soil temperature and soil CO2 efflux in plots A and B were weak (R= 28.0 % and R=30.6 %), respectively, however the correlation between soil humidity and soil CO2 efflux was weak (R=12.5%) in the control plot and moderate (R=49.7%) in the plot B. The correlations of the soil respiration with the total biomass weight were moderate in both plots (R=48 % and R=43 %), respectively.