Seasonal Patterns of Evapotranspiration for a Vochysia divergens Forest in the Brazilian Pantanal

The recent and widespread expansion of the pioneer tree species Vochysia divergens Pohl into western Brazil has the potential to significantly alter the structure and function of the Pantanal—a UNESCO World Heritage Site and the World’s largest tropical wetland. Here we assess the seasonal pattern of evapotranspiration ( ET ) and micrometeorological variables of V. divergens (locally known as cambarazal ), located in the Northeast of the Brazilian Pantanal. ET was calculated from a number of micrometeorological measurements recorded between January 2007 and January 2008. The results indicate that ET was the dominant sink for net radiation ( R n ) during the wet and dry seasons, primarily because the forest was either flooded (December–May) or retained a high level of soil moisture. ET decreased during the dry season due to a decline in R n and surface water availability, and an increase in atmospheric vapor pressure deficit. Based on this analysis we conclude that the spread of V. divergens into the Pantanal and the associated high rates of ET are due in part to high water availability, even during the dry season, and the consistently high leaf area index that increases the transpiration surface area when the water table is below the soil surface.