Dinâmica de fluxos de energia e CO2 em sistemas agrícolas com rotação de culturas no Sul do Brasil utilizando o método eddy covariance

Abstract

Analysis of carbon and heat fluxes in cropping systems is important for understanding the impacts of different management practices and meteorological conditions, in the context of climate change, on agriculture. We have established a pair of long-term eddy covariance flux towers at the Cooperativa Central Gaúcha Ltda Tecnologia (CCGL-Tec) in Cruz Alta, Rio Grande do Sul, Brazil. The tower sites have similar crop rotation, weather conditions, and management practices except tillage. One site has been under no-till management (PD) since 2011, while the other site has used conventional tillage practice (PC) over the same time period. Measurements conducted above a set of crops (wheat, soybean, oat, soybean) between June 2011 and april 2013 showed the PD and PC sites acted as sinks of CO2 with an cumulative flux of carbon on PD between 16% to 30% greater than in PC. The mean and cumulative values at each site were significantly different (p < 0; 05). Two analytical models based on analytical solutions of the advection-diffusion equation were applied to estimate the footprint and thus to identify flows from the plots of interest in the study. In summary, the site deploying no-till practices had greater uptake of carbon throughout the measurement period than conventional tillage site, even when the footprint analysis was applied resulting in overestimation of the percentages of uptaken carbon by PD. In this work are quantified the carbon flux and some of the components of the energy balance (latent and sensible heat flux) for two agricultural sites with different types of crops; two models are applied to estimate the footprint and to observe which of them allows to select the largest amount of data coming from the crops of interest only: If the different flows between the no-tillage and conventional plantings are compared and the relationships between the surface fluxes in each culture system.