Effect of contrasting irradiances on the carbon balance and biomass partition in Brazilian savanna (Cerrado) woody seedlings
Carlos
Henrique
Prado, Universidade Feceral De São Carlos, caique@power.ufscar.br
(Presenting)
Carlos
Cesar
Ronquim, Universidade Feceral De São Carlos, pccr@iris.ufscar.br
The photosynthetic capacity of Cerrado woody species is not low (6-17 mmol m-2 s-1). Besides, around a half of biomass in Cerrado woody species is allocated belowground in order to overcome soil deficiency, fire, and drought. Considering this behavior and the vast Cerrado´s area (similar to East Europe) this biome could be an important continental sink to CO2. On the other hand, the responses facing specific constraints (e.g. shade, mineral deficiency) must be quantified in order to estimate the real capacity of each Cerrado species to act as a carbon sinker. Studying several levels of organization at same time it was possible to point out how phenotypic plasticity operates in three young Cerrado woody species submitted to different irradiance and under transitory increasing of atmosphere CO2 availability. Under full irradiance, photosynthetic capacity, leaf area, and carboxilation efficiency increased at least two times in comparison to same species growing in shade (under Cerradão irradiance attenuation). As a consequence, biomass production was always greater (p<0.05) under full irradiance (FI) till 570 days after sowing (DAS). Photosynthetic capacity under 1600 ppm of CO2 was at least two times higher in comparison to regular CO2 availability irrespective the irradiance treatment. In addition to leaf physiological alterations, height, stem diameter and specific leaf mass values were also significantly lower in all species in shade. These physiological and morphological alterations could enable some Cerrado woody species to survive under Cerradão irradiance attenuation working as a carbon sinker even in the densest Cerrado physiognomy.
Submetido por Carlos Prado em 18-MAR-2004
Tema Científico do LBA: CD (Armazenamento e Trocas de Carbono)