A Look at Amazon Basin Seasonal Dynamics with the Biophysical ...

VARIABILITY OF SOIL RESPIRATION OVER WOODLAND SAVANNAH (CERRADO)AND SUGAR CANE IN SOUTHEAST BRAZILRafael Rosolem, Humberto da Rocha, Helber Freitas Instituto de Astronomia, Geofísica e CiênciasAtmosféricas Universidade de São Paulo São Paulo, BrasilWe report a time series of soil CO2 efflux observations, monitored at ecosystems of Cerrado(woodland savannah) and Sugar Cane crop, in the state of São Paulo, Brazil, during April 2001 toMarch 2002. The data was collected using a static soil chamber (PPSystem) with EGM-2 infra-redgas analyser, over 17 (seventeen) rings each site, on a weekly basis. Measurements of soiltemperature (Campbell 107) at 1 cm and soil moisture (10 and 20 cm) (Campbell frequency domainreflectomere CS615-G) were measured automatically using a CR10X datallogger (CampbellSystems). The data has shown the average carbon emissions were substantially larger at the Cerradosite (4,75 ± 2,18 µmol m 2 s - ) than at the sugar cane (2,23 ± 1,59 µmol m 2 s - ). The correlationbetween soil respiration and temperature appeared to be well fitted on an exponential curve at theCerrado, as opposed to the sugar cane, where the statistical variation appeared larger. Theseasonality is strong and the soil moisture is substantially well correlated (on a near-linear mode) atboth sites. While it appears the correlations at the undisturbed Cerrado are easier to fitmathematically, the modelling at crop sites (sugar cane) faces several resistances, as of radicalchanges in phenology and canopy cover, and others of management (e.g. plowing).