What controls the seasonality of photosynthesis across the Amazon basin? A cross-site analysis of eddy flux tower measurements from the BrasilFlux network
Natalia
Restrepo-Coupe, Dept. of Dept. of Ecology and Evolutionary Biology, ncoupe@email.arizona.edu
Humberto
da Rocha, Dept. of Atmospheric Sciences, Universidade de São Paulo, humberto@model.iag.usp.br
Scott
R.
Saleska, Dept. of Ecology and Evolutionary Biology, saleska@email.arizona.edu
(Presenting)
Alessandro
C.
da Araujo, National Institute for Space Research (INPE), Belem, alessandro.araujo@falw.vu.nl
Laura
S.
Borma, Escola de Artes, Ciências e Humanidades da Universidade de São Paulo, laura@uft.edu.br
Osvaldo
M. R.
Cabral, Embrapa Meio Ambiente, ocabral@cnpma.embrapa.br
Plinio
B.
de Camargo, Dept. of Atmospheric Sciences, Universidade de São Paulo, pcamargo@cena.usp.br
David
R.
Fitzjarrald, Atmospheric Sciences Research Center, State University of New York, fitz@asrc.cestm.albany.edu
Michael
L.
Goulden, Dept. of Earth System Science, University of California Irvine, mgoulden@uci.edu
Lucy
R.
Hutyra, University of Washington, lrhutyra@u.washington.edu
Bart
Kruijt, Alterra, Wageningen University and Research Centre, bart.kruijt@wur.nl
Jair
M. F.
Maia, Instituto Nacional de Pesquisas da Amazônia (INPA), jairmaia@inpa.gov.br
Yadvinder
S.
Malhi, Oxford University Centre for the Environment, yadvinder.malhi@ouce.ox.ac.uk
Antonio
O.
Manzi, Instituto Nacional de Pesquisas da Amazônia (INPA), manzi@inpa.gov.br
Antonio
D.
Nobre, Instituto Nacional de Pesquisas da Amazônia (INPA), anobre@ltid.inpe.br
Celso
von Randow, Alterra, Wageningen University and Research Centre, cvrandow@gmail.com
Ricardo
K.
Sakai, Atmospheric Sciences Research Center, State University of New York, sakai@asrc.cestm.albany.edu
Julio
Tota, Instituto Nacional de Pesquisas da Amazônia (INPA), tota@inpa.gov.br
Steven
C.
Wofsy, Division of Applied Sciences, Harvard University, wofsy@fas.harvard.edu
Fabricio
B.
Zanchi, Vrije Universiteit Amsterdam, fabricio.zanchi@falw.vu.nl
Scott
D.
Miller, Atmospheric Sciences Research Center, State University of New York, smiller@albany.edu
Amazonian forests play an important role in global carbon cycling, contributing substantially to increases (via land use change emissions) and possibly to net sequestration (in intact forests) of atmospheric CO2. However, model skill at predicting seasonality of photosynthetic metabolism in the Amazon, a first-order test of our understanding of a process critical to carbon sequestration, is limited. To enhance our understanding of these processes, we investigated the seasonal and spatial patterns of Amazonian forest photosynthetic activity, and the effects of land-use conversion thereon, by integrating data from a network of ground-based eddy flux towers in Brazil. The BrasilFlux towers, a legacy of the "Large-Scale Biosphere Atmosphere Experiment in Amazonia" (LBA) project have now produced multiyear datasets. We found that the pattern of photosynthesis at towers across the equatorial Amazon (5°N–5°S) shows little evidence of seasonal water limitation, as they sustain high – or even increasing – levels of GEP as the dry season progresses. Towers along the southern flank of the Amazon, in converted pasture sites, and in savanna, by contrast, exhibit seasonal patterns consistent with varying degrees of water stress. In contrast to studies of Amazon evapotranspiration, which is consistently highly correlated with available energy (net radiation), Amazon ecosystem photosynthetic flux surprisingly showed no simple relationship with measures of available energy. Based on results of a simple model of leaf-flush at a central Amazon site, we hypothesize that the seasonality of Amazon photosynthesis is controlled by the interaction of adaptive mechanisms (which biologically determine the seasonality of leaf flush and litter fall) and sunlight availability (which determines the fraction of photosynthetic capacity utilized). Equatorial climates advantage vegetation that can grow leaves in the dry season, when surface solar radiation peaks, but southerly sites may not because of reduced seasonality in surface radiation.
NASA Carbon Cycle & Ecosystems Active Awards Represented by this Poster: