Modifications in Soil Hydrology Due to Land-Use Changes in Southeastern Brazil
Abstract
In many areas of southeastern Brazil, like those located in the hilly topography of the Serra do Mar in Rio de Janeiro state, the native rain forest has been gradually replaced by farming activities. Such changes usually generate a variety of modifications in the upper portions of the soil profile that tend to reduce infiltration rates and to increase overland flow and soil erosion. In order to characterize the effects that recent land-use changes, mainly induced by the expansion of farming and urbanization, generated on soil hydrology we carried out field experiments and started a soil-water monitoring program. For the main classes of soil type and soil cover and/or land-use (farming, natural forest, 15-years regenerated forest, 40-years regenerated forest and grazing) we measured the infiltration rate and the field-saturated hydraulic conductivity (kfs) using a double-ring infiltrometer and a Guelph permeameter (20 and 50 cm depths), respectively. Besides, soil-water potential (SWP) was continuously monitored using nests of sensors installed at different depths (10, 20, 50 and 80 cm). Undisturbed soil samples were collected at these depths to characterize soil physical properties in the laboratory. All the experiments, the SWP monitoring and the soil analyses were carried out with two repetitions. The results, although preliminary, suggest that under natural forest kfs values tend to decrease with depth (from 5.0 to 0.21 x10-6 cm/s) while for those under farming activities, on the contrary, they tend to increase with depth (from 1.4 to 22.0 x10-6 cm/s). Infiltration rates are higher in soils under native forest (from 100 to 180 cm/h) than those under farming (from 24 to 36 cm/h), while recently ploughed areas show intermediary values (from 48 to 72 cm/h). SWP results attest that grazing and farming activities retain more water in the first meter of the soil profile than forest. The results, although preliminary, attest the role played by land-use changes in modifying soil hydrology in this area.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.H51A0872F
- Keywords:
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- 1803 HYDROLOGY / Anthropogenic effects;
- 1838 HYDROLOGY / Infiltration;
- 1866 HYDROLOGY / Soil moisture