Abstract

ZERMENO-GONZALEZ, Alejandro et al. Dynamics of the energy and carbon dioxide flux above a natural grassland of northern Mexico. Bioagro [online]. 2011, vol.23, n.1, pp.35-42. ISSN 1316-3361.

As the grassland covers a significant fraction of the continental surface, they may have an important contribution to the sequestration of atmospheric carbon dioxide. For this reason, the objective of this research was to use the eddy covariance method to measure the flux of carbon dioxide (CO₂) and energy (net radiation, sensible heat, latent heat and soil heat flux), above a natural grassland of northern Mexico, to evaluate the rate of CO₂ assimilation by the vegetated surface and the partitioning of the energy fluxes. The CO₂ assimilation rate by the grassland was up to 18 µmol·m^-2 s^-1. The average daily retention of CO₂ by the grassland (difference between assimilation during daytime and release during nighttime) was 123,081 mmol·m^-2, which corresponded to a daily average of 54.12 kg·ha^-1. This shows the importance of this ecosystem in the sequestration of atmospheric carbon dioxide. The intrinsic water use efficiency and the energy use efficiency were higher in cloudy days than under conditions of clear sky. Net radiation over the vegetated surface was mainly dissipated in latent heat flux, sensible heat flux and in a smaller rate in soil heat flux. This showed the importance of evapotranspiration on dissipating the absorbed radiation by the vegetated surface.

Keywords : Energy balance; eddy covariance; photosynthesis.