CO2 exchanges and evapotranspiration of a grazed pasture under tropical climate conditions

Studies concerning the role of livestock farming on the regional budget of CO2 in Northeast of Brazil are scarce. Thus, our main objective was to evaluate the variability of CO2 exchange and evapotranspiration (ET) of a cultivated tropical forage C4 grass (Brachiaria brizantha) grazed by sheep for meat production. The experiment was conducted during the period from 2015-oct-01 to 2017-sep-30 using an eddy covariance flux tower. The pasture acted as a moderate CO2 sink, with mean annual net ecosystem exchange of -215 +/- 22 g C m(-2)y(-1), while the average uncertainty associated with the calculation procedure was 15 g C m(-2) +/- 7.20% of NEP. The mean annual ET was 967 +/- 245 mm. Carbon use efficiency at the ecosystem level was 0.20 +/- 0.03, which is more efficient compared to similar experiments in grazed environments around the world. Water use efficiency at the ecosystem level was 1.14 +/- 0.01 g C (kg H2O)(-1).

Automated summary

This study evaluates the impact of livestock farming on CO2 emissions budget in the Northeast region of Brazil. The research finds that grazed tropical forage has a higher carbon use efficiency and acts as a moderate CO2 sink.