The effects of Fire Disturbance on Soil Water Cycling of a Southeast Amazonian Forest

Tuesday, 16 December 2014
Claudinei Santos1, Michael Thomas Coe2, Susan Trumbore3, Paul Lefebvre4, Divino Vicente Silverio5, Marcia Macedo4 and Paulo M Brando1,6, (1)IPAM Amazon Environmental Research Institute, Brasilia, Brazil, (2)The Woods Hole Research Center, Falmouth, MA, United States, (3)Max Planck Institute for Biogeochemistry, Jena, Germany, (4)Woods Hole Research Center, Falmouth, MA, United States, (5)UNB University of Brasilia, Brasília, Brazil, (6)Carnegie Institution for Science, Washington, DC, United States
Fire disturbances can reduce the capacity of tropical forests to cycle water from the soil to the atmosphere, but our understanding of this process remains poor. To address this gap, we studied the effects of fire-related changes in vegetation structure and dynamics on soil water cycling of a transitional forest located between Amazônia and Cerrado, Mato Grosso, Brazil. In particular, we measured monthly soil moisture (from 1 to 9 m depth) using seven soil water pits that were distributed across three 50-ha plots: a plot that represented an unburned control; a plot that was burned in 2004, 2007 and 2010; and, a plot that was burned annually from 2004 to 2010, with exception of 2008. Measurements of soil moisture began after the experimental fires of 2010 (in mid September) and continued until December 2013. We hypothesized that soil moisture would be higher in the burned plots than in the control due to fire-induced reductions in evapotranspiration. Our preliminary results provide only partial support for this hypothesis. We observed a high variability in soil moisture between treatments, among months, and across years. For example, the unburned control tended to hold more soil water throughout the soil profile in wet-season months. However, soil moisture tended to be higher in the experimentally burned plots during the driest months of the year (August and September), but this pattern was no consistant across drought and non-drought years. These results show that fires exert complex influences on the soil water cycling of this transitional forest, perhaps even promoting increased evapotranspiration in the burned plots due to reduced competition among trees for resources.