Net carbon dioxide exchange in a hyperseasonal cattle pasture in the northern Pantanal wetland of Brazil

In this study, the authors measured CO₂_C fluxes using eddy covariance over a hydrological year on pastures within a cattle farm in the Brazilian Pantanal that experienced seasonal flooding. Their measurements show that seasonally flooded pastures were large emitters of CO₂_C, contributing 337 g CO₂_C m⁻² year⁻¹ to the atmosphere.

During flooding, when the soils were anaerobic, and soil O₂ was close to zero, the flooded pasture was a net sink of -18 g CO₂_C m⁻², while during the aerobic phase (soil O₂ > 15%) the pasture was a significant CO₂ source to the atmosphere (301 g CO₂_C m⁻²). Transitions to and from anaerobic conditions corresponded to 54 g CO₂_C m⁻².

The results indicate that the seasonally flooded cattle pastures in the Brazilian Pantanal may be an important regional source of CO₂_C for the atmosphere. Better management, and use of drought resistant grasses, may be a way to improve soil C stocks and limit emissions, especially as global climate change is anticipated to increase heating and drying for the Pantanal biome.

Highlights

• CO₂ flux was measured with eddy covariance in a seasonally flooded pasture.
• The pasture was a large C emitter, emitting 337 g CO₂_C m⁻² y⁻¹ to the atmosphere.
• The pasture was a C sink when soil was anaerobic but a source when soil was aerobic.
• Low productive pastures in the Pantanal may be important sources of atmospheric CO₂.
• Management and altered hydrology of Pantanal pastures can reduce net CO₂ uptake.