Land-use conversions from managed grasslands to croplands in Uruguay increase medium-term net carbon emissions to the atmosphere

ABSTRACT Globally, significant land conversions of traditionally managed temperate grasslands to croplands were taking place. Among these is South-Central Uruguay where changes in recent decades have highly likely impacted plant productivity, soil quality, and carbon fluxes at a regional scale. A geospatial version of the biophysical model EPIC was developed and validated (Geospatial-EPIC-UY). An analysis of the potential impact of the land use change on the carbon fluxes was performed, considering the conversion of all the suitable cropping areas over a 15-year period. Modeled net ecosystem exchange (NEE) showed that, on average, grasslands C emissions were close to neutral (0.1 Mg CO2 ha−1 year−1), while croplands contributed almost 7 times this value. Also, the inter-annual variation of grassland NEE was significantly less than that of the cropland. These results highlight the potential C losses under extended land conversions, which could be attenuated or even reverted if best management practices were implemented.