CICLO DE CARBONO EN LA ATMÓSFERA: EFECTO DE LAS VARIABLES METEOROLÓGICAS Y DEL SUELO EN UN ECOSISTEMA DE MARISMA

NAHUEL BAUTISTA; GASSMAN, M.I.; PÉREZ C F

Congreso; CONGREMET XIV; 2022

The processes that explain the net flux of CO2 (NEE) on vegetated surfaces are respiration(Reco) and photosynthesis (GPP). These processes show dependence on their previoushistory, which manifests itself as a delay in the effect over the cause that produces it(hysteresis). In this work, the hysteresis between NEE, Reco, and GPP with respect toatmospheric and soil variables at Mar Chiquita (Buenos Aires, Argentina) salt marsh wasstudied for two sunny days with and without precipitation during the previous 48 h. NEE wascalculated with the Eddy Covariance technique, Reco was estimated following the Lloyd andTaylor model and GPP was calculated by difference. The day with the driest soil showed agreater gap in the response of NEE, Reco, and GPP with respect to their forcing variables.GPP responded to radiation, with greater dispersion being observed for levels higher than1000 μmol m-2 s-1, which would correspond to the difference in the photosynthetic saturationrates of the main C4 and secondary C3 plants that inhabit the area. GPP grew rapidly duringthe morning against small increases in soil or air temperature, was constant through themiddle of the day, and decreased rapidly when both temperatures were maximum. Recoresponded to air and soil temperature, possibly with a greater contribution from the soil thanplant respiration because of its greater hysteresis loop area against soil temperature. It alsoshowed a linear response to air temperature because the Lloyd and Taylor model uses thatvariable to estimate Reco. NEE cycles were similar to that observed for GPP.