Impact of Deforestation on Size-Density Carbon Fractions in Soils of Bahia Brazil. (S07-santos824666-oral)
Authors:
I.S. Matias* - Univ. Fed. Bahia J.A.G. Santos - Univ. Fed. Bahia N.B. Comerford - Univ. FL J.O. Resende - Univ. Fed. Bahia
Abstract:
The Atlantic Forest once represented about 15% of Brazil, but today occupies less than 8% of its original area. The remaining forest is considered a ‘hotspot’ of biodiversity having more than 450 plant species ha-1. The present study evaluated the influence that land use change has had on soil organic carbon (SOC) and the distribution of SOC between size-density fractions. Three ecosystems, a native Atlantic Forest, a 30-yr old Brachiaria decumbens pasture and a Eucalypt plantation established in an area previously under degraded Brachiaria decumbens pasture, all on a Yellow Latossol with a coeso layer in Bahia, were used for this comparison. Soil samples collected from the surface 10 cm from each ecosystem were dispersed in a sodium hexametaphosphate solution and separated by sieving and flotation with water into six size-density fractions. The light fractions in the natural forest ecosystem were two and twelve times greater than that found in the soil under Eucalypt and degraded pasture.
Conversion to pasture reduced SOC in the clay + silt fraction from 70 to 3 mg g-1. Conversion of pasture to Eucalypt increased it to 10 mg g-1. The relative difference in SOC between land uses is also seen in the root mass with native forest (16400 kg m-2) greater than Eucalypt (10400 kg m-2) greater than Pasture (3800 kg m-2). Extensive pasture degrades SOC that is inherently high under native forests. Eucalypt is a useful alternative for rehabilitating degraded pastures.
Speaker Information: Jorge Santos, Univ. Fed. Bahia, PO Box 110290 Soil and Water Science Department , Gainesville, FL 32611-0290; Phone: 352-392-1951; E-mail: [email protected]
Session Information: Monday, November 3, 2003, 7:55 AM-10:00 AM Presentation Start: 9:15 AM
Keywords: Eucalyptus; Native Forest; Pasture; Carbon Sequestration