A Look at Amazon Basin Seasonal Dynamics with the Biophysical ...

Transpiration before and after Burning in Different “Cerrado” Vegetation Typesof the Brazilian SavannaViviana Horna , Jonathan J. LloydMax Planck Institute for Biogeochemistry, Carl Zeiss Promenade 10, 07701 JenaGermanyviviana.horna@bgc-jena.mpg.deThe savanna vegetation in Brazil, also known as Cerrado, has been estimated to cover 1.8mil km 2 . This large ecosystem is dominated by fire and composed by a successional seriesthat varies in species composition and tree density. In this study, the effects of fire on therates of xylem flux density will be compared by measuring the flow of xylem water intrees before and after fire occurrence at two cerrado vegetation types: campo sujo (treeand/or shrub savanna) and cerrado (wooded savanna). The study is being conducted at theReserve of the Brazilian Institute for Geography and Statistics located 34 Km south of thecity of Brasilia. Nine trees of the most common tree species are monitored at each site.Sensors to measure xylem flux density and stem temperature were installed at all sitesduring mid April. One Campo sujo site and one Cerrado site will be burned during midJune 2002, following a bi-annual plan for prescribed fires managed by the University ofBrasilia. Xylem sensors will be removed just before the fire and reinstalled after the firein the two areas to be burned, while measurements will continue uninterrupted in twocontrolled areas.At the moment, the first results from the early dried season before fire are beingprocessed and these will be compared to the data to be collected in late June for the postfireperiod. It is expected that fire will reduce considerably the values of xylem fluxdensity. The data from this study will help to determine the degree of adaptation ofCerrado tree species to fire, measured by the level and speed of recovery of the xylemflux rates after the fire.