Seasonal variations in C and H2O cycling of a tropical transitional forest
George
Louis
Vourlitis, Department of Biological Sciences, California State University, San Marcos, CA 92096, USA., georgev@csusm.edu
(Presenting)
Nicolau
Priante Filho, Departamento de Fisica, Universidade Federal de Mato Grosso, Cuiaba, MT, Brasil, nicolaup@terra.com.br
José
de Souza
Nogueira, Departamento de Fisica, Universidade Federal de Mato Grosso, Cuiaba, MT, Brasil, nogueira@cpd.ufmt.br
Luciana
Sanches, Departamento de Fisica, Universidade Federal de Mato Grosso, Cuiaba, MT, Brasil, lsanches@cpd.ufmt.br
Fernando
Raiter, Instituto Universitario do Norte Matogrossense, Universidade Federal de Mato Grosso, Sinop, MT, Brasil, raitersn@terra.com.br
Wander
Hoeger, Instituto Universitario do Norte Matogrossense, Universidade Federal de Mato Grosso, Sinop, MT, Brasil, wander_hoeger@yahoo.com.br
Eduardo
Jacusiel
Miranda, Departamento de Fisica, Universidade Federal de Mato Grosso, Cuiaba, MT, Brasil, aquaviva@zaz.com.br
George
Sanches
Suli, Departamento de Fisica, Universidade Federal de Mato Grosso, Cuiaba, MT, Brasil, suli@terra.com.br
Carla
Valentini, Departamento de Fisica, Universidade Federal de Mato Grosso, Cuiaba, MT, Brasil, valentini@vspmail.com.br
Measurements of net ecosystem CO2 exchange and evapotranspiration of a tropical transitional (ecotonal) forest near Sinop-MT were made between August 1999-present using eddy covariance measurement techniques. Measurements of leaf photosynthesis, plant water potential, soil respiration, and litter fall were also made to determine how component C and/or H2O fluxes contributed to the temporal patterns in forest CO2 and H2O exchange. Data indicate that leaf and forest gas exchange is strongly affected by seasonal variations in rainfall. For example, leaf gas exchange and water potential and soil respiration are on average 2-fold lower while litter fall is 4-5 times higher during the dry season (June-August). While variations in maximum gross primary production (Gmax), canopy conductance (gC) and ecosystem respiration (R0) also followed trends in rainfall, variations in these whole-forest indices of gas exchange tended to lag behind rainfall by 1-2 months. These data suggest that seasonal variations in rainfall affect canopy CO2 and H2O exchange processes in a complex manner. Furthermore, comparisons between the transitional forest and less seasonal rain forests suggest that the magnitude in the seasonal variation in CO2 exchange is somewhat unique to the transitional forest. These data suggest that potential warming and drying of tropical forest may cause seasonal variations in CO2 and H2O vapor exchange to increase in the future.
Submetido por George L. Vourlitis em 15-MAR-2004
Tema Científico do LBA: CD (Armazenamento e Trocas de Carbono)