Mangrove forests: what mechanism(s) underly seasonal changes in productivity and evapotranspiration? Evidence from plant physiology and eddy covariance studies.
Patrick
Meir, University of Edinburgh UK, pmeir@ed.ac.uk
(Presenting)
Jose Maria
Nogueira da
Costa, Universidade Federal de Vicosa, jmncosta@ufv.br
Mathew
Williams, University of Edinburgh UK, mat.williams@ed.ac.uk
Yadvinder
Singh
Malhi, University of Edinburgh UK, ymalhi@ed.ac.uk
Rosie
Alice
Fisher, University of Edinburgh UK, rosie.fisher@ed.ac.uk
Antônio
Carlos Lôla da
Costa, Universidade Federal de Para, lola@ufpa.br
João
Athaydes
Silva Jr, Universidade Federal de Para, athaydes@ufpa.br
Vanda
Andrade, Universidade Federal de Vicosa, jmncosta@ufv.br
Rommel
Benicio Costa
Silva, Universidade Federal de Vicosa, rbcsilva@yahoo.com.br
Raquel
Lobo do
Vale, Instituto Superior de Agronomia, Portugal, raquelvale@isa.utl.pt
Rafael
Costa, Museu Paraense Emilio Goeldi, Para, jmncosta@ufv.br
Luiz
Eduardo Oliveira Cruz de
Aragão, INPE, aragao@ltid.inpe.br
Eleneide
Doff
Sotta, University of Gottingen, Germany, esotta@gwdg.de
Paulo
Jorge
Oliveira, Universidade Federal Rural da Amazonia, pj@ufra.edu.br
Very few eddy covariance studies have been made over mangrove forest and yet mangroves line up to 75% of tropical coastlines. We present a measurement and modelling analysis of the first such measurements from S. America, obtained by our UFV- and UFPa-led team from a site affected by seasonal changes in Amazon outflow, near Braganca, in Pará, NE Brazil,. We combine this information with plant physiological data on the exchange of water and carbon by leaves and whole trees, using leaf gas exchange and sap flux measurements. Tree-level sapflux data are upscaled to calibrate our soil-plant-atmosphere model, SPA, which permits us to run SPA and estimate gross primary production (GPP) as well as the transpiration flux from mangrove forest. Successful calibration of SPA also allows us to probe the mechanisms of seasonal changes in forest physiology. We compare the outputs of our upscaled sap flux data and our SPA output with eddy covariance data for the same site. Eddy flux data at this site are relatively ‘clean’ because of the relatively high turbulence experienced during the night as well as the day, which encourages strong canopy-atmosphere coupling. The eddy data show clear increases in NEE and GPP during the transition from dry season to wet season. In contrast, the sap flow data and SPA model output do not show significant increases in transpiration and GPP. This contrast in results leads to an analysis using additional leaf physiological (photosynthetic biochemistry and stomatal conductance), canopy structural and water salinity data. We discuss the evidence available to us, which suggests that the increase in GPP reflects a biochemical response in photosynthetic capacity in conjunction with wet-season reductions in water salinity. Mechanistic representation of this response will improve our ability to model mangrove forest - atmosphere exchanges of mass and energy.
Submetido por Patrick Meir em 25-MAR-2004
Tema Científico do LBA: CD (Armazenamento e Trocas de Carbono)