COSTA, A. da

ELIANE, M.

FELSEMBURGH, C.

JANS, W.

KRUIJT, B.

MEIR, P.

ROWLAND, L.

TRIBUZY, E.

VASCONCELOS, S.

Repository Open Access to Scientific Information from Embrapa

 Monday, December 15, 2014 08:00 AM - 12:20 PMMoscone WestPoster HallIn many dynamic vegetation models, degradation of the tropical forests is induced becausethey assume that productivity falls rapidly when temperatures rise in the region of 30-40°C.Apart plant respiration, this is due to the assumptions on the temperature optima ofphotosynthetic capacity, which are low and can differ widely between models, where in facthardly any empirical information is available for tropical forests. Even less is known about thepossibility that photosynthesis will acclimate to changing temperatures. The objective of thisstudy to is to provide better estimates for optima, as well as to determine whether anyacclimation to temperature change is to be expected.We present both new and hitherto unpublished data on the temperature response ofphotosynthesis of Amazon rainforest trees, encompassing three sites, several species andfive field campaigns. Leaf photosynthesis and its parameters were determined at a range oftemperatures. To study the long-term (seasonal) acclimation of this response, this wascombined with an artificial, in situ, multi-season leaf heating experiment.The data show that, on average for all non-heated cases, the photosynthetic parameterVcmax weakly peaks between 35 and 40 ˚C, while heating does not have a clearly significanteffect. Results for Jmax are slightly different, with sharper peaks. Scatter was relatively high,which could indicate weak overall temperature dependence. The combined results were usedto fit new parameters to the various temperature response curve functions in a range ofDGVMs. The figure shows a typical example: while the default Jules model assumes atemperature optimum for Vcmax at around 33 ˚C, the data suggest that Vcmax keeps risingup to at least 40 ˚C. Of course, calculated photosynthesis, obtained by applying this Vcmaxin the Farquhar model, peaks at lower temperature. Finally, the implication of these newmodel parameters for modelled climate change impact on modelled Amazon forests will beassessed, where it is expected that predicted die-back will be less.AuthorsWilma JansAlterraSteel VasconcelosEMBRAPA Brazilian Agricultural Research CorportationEdgard TribuzyUniversidade Federal do ParaCristina FelsemburghUniversidade Federal do ParaMelem ElianeEMBRAPA Brazilian Agricultural Research CorportationLucy RowlandUniversity of EdinburghAntonio da CostaUFPA Federal University of ParaPatrick MeirUniversity of EdinburghBart KruijtAlterraBack to: Steel VasconcelosB11G-0125 New estimates of temperature response of leaf photosynthesis in Amazonforest trees, its acclimation to mean temperature change and consequences for modellingclimate response to rain forests.

New estimates of temperature response of leaf photosynthesis in Amazon forest trees, its acclimation to mean temperature change and consequences for modelling climate response to rain forests.

New estimates of temperature response of leaf photosynthesis in Amazon forest trees, its acclimation to mean temperature change and consequences for modelling climate response to rain forests.

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