HR: 1340h
AN: B33D-1061    [Abstracts]
TI: Vegetation Patterns Coupled to Deep Soil Water in a Brazilian Savanna
AU: Ferreira, J N
EM: joiceferreira@unb.br
AF: Universidade de Brasilia, Departamento de Ecologia, Brasilia, DF 70919-970 Brazil
AU: Bustamante, M M
EM: mercedes@unb.br
AF: Universidade de Brasilia, Departamento de Ecologia, Brasilia, DF 70919-970 Brazil
AU: Garcia-Montiel, D C
EM: dgarcia@unb.br
AF: Universidade de Brasilia, Departamento de Ecologia, Brasilia, DF 70919-970 Brazil
AU: Garcia-Montiel, D C
EM: dgarcia@unb.br
AF: Woods Hole Research Center, PO Box 296, Woods Hole, MA 02543 United States
AU: Simpson, P L
EM: none
AF: Universidade de Brasilia, Departamento de Ecologia, Brasilia, DF 70919-970 Brazil
AU: * Davidson, E A
EM: edavidson@whrc.org
AF: Woods Hole Research Center, PO Box 296, Woods Hole, MA 02543 United States
AB: Soil water content is an important factor controlling plant productivity, phenology, and species composition in savannas, but spatial and temporal variation and the depth of soil water resources are difficult to measure. We used 2-D soil electrical resistivity profiling technique to estimate seasonal plant available water (PAW) along three 275-m transects in the core of the Brazilian savanna (Cerrado). A continuous current was injected into the ground and the resulting voltage differences were measured using an array of electrodes inserted into the soil surface. Electrical resistivity values were converted to PAW estimates using calibration curves derived from time domain reflectometry measurements of volumetric water content and from soil water holding characteristics. Deep soil PAW varied among and within transects, and PAW varied seasonally to about 10-m soil depth in all transects, indicating that the plants were using water resources to this depth. To explore the implications of this variation in PAW, we described vegetation properties across transects (220 m x 10 m) centered along the measured profiles. PAW in the deep soil layers (4-10 m) during the dry season was related to species composition. Species density increased slightly with higher PAW in upper soil layers (0-7 m), whereas tree density increased with deep PAW in the wet season. Crown depth was negatively correlated with deep soil (4-10 m) PAW in both seasons. Interpretation of these relationships is complicated by the fact that, while the vegetation may respond positively to the presence of a deep soil water resource, the evapotranspirational demand of the vegetation may also draw down the water resource. Further application of this new method for imaging seasonal variation of deep soil water resources may help explain spatial and temporal variation of vegetation properties within and among savannas.
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0476 Plant ecology (1851)
DE: 0486 Soils/pedology (1865)
DE: 1813 Eco-hydrology
DE: 1851 Plant ecology (0476)
SC: Biogeosciences [B]
MN: Fall Meeting 2005