PARENT SESSION
Poster Session 37: Forest Ecology.
Thursday, August 5 Presentations from 5:00 PM to 6:30 PM, Exhibit Hall A 1.
Effect of rainfall exclusion on soil moisture movement and depth of water uptake by Amazonian trees.
Romero-Saltos, Hugo*,1, Sternberg, Leonel1, Moreira, Marcelo2, Nepstad, Daniel3, 1 University of Miami, Coral Gables, Florida, USA2 Universidad de São Paulo (CENA), Piracicaba, São Paulo, Brazil3 The Woods Hole Research Center, Woods Hole, Massachusetts, USA
ABSTRACT- At the beginning and end of the 2002 wet season, deuterium-labeled water was sprinkled around Coussarea racemosa, Sclerolobium chrysophyllum and Eschweilera pedicellata trees to study the effect of the Tapajós Throughfall Exclusion Experiment on soil moisture movement and depth of water uptake. Since February 2000, this experiment simulates an extended drought in eastern Amazonia that may be intensified by global climate change during El Niño years. The soil of the treatment plot (1-ha) is covered by plastic panels during the wet season, excluding 60% of throughfall, while the control plot (1-ha) receives normal precipitation year-round. Results showed that the mean percolation rate in the control plot was greater than in the treatment plot during the wet season (0.75 vs. 0.07 m/month), but it was similar for both plots during the dry season (0.15 m/month). The deuterium-labeled water in the control plot moved upwards during the dry season, from around 2.5 to 2 m. A capillary rise phenomenon, not hydraulic lift, is a most consistent explanation for this pattern. Upward water movement probably also occurred in the treatment plot, but was not detectable because the label in this plot never moved below 1 m depth. At the end of the wet season and throughout the dry season, treatment trees, as expected, tapped water significantly deeper, but never >1.5 m, than control trees. This pattern was consistent among species, and therefore may be representative of expected root function of the understory/sub-canopy tree community in this forest during dry periods.
Key words: Sclerolobium chrysophyllum, Amazonian drought-El Niño, Coussarea racemosa, Eschweilera pedicellata