Although the strong influence of vegetation shaping the hydrological cycle is increasingly recognized, the effects of land-use changes in very flat regions (i.e., hyperplains, regional slope <0.1%) are less understood in spite of their potentially large magnitude. In hyperplains with sub-humid climates, long-lasting flooding episodes associated to water-table raises are a distinctive ecohydrological feature and a critical environmental concern. We evaluated the hydrological impacts caused by the replacement of livestock systems, dominated by perennial alfalfa pastures, by grain production systems, dominated by annual crops, that have been taking place in the Pampas (Argentina). For this purpose, we combined remote sensing estimates of vegetation transpiration and surface water coverage with long-term (1970–2009) hydrological modeling (HYDRUS 1D), and water-table depth and soil moisture measurements. The NDVI derived from MODIS imagery was 15% higher in dairy systems than in grain production ones, suggesting higher transpiration capacity in the former (852 vs. 724 mm y−1). Even higher contrasts were found among individual cover types, with perennial pastures having the highest NDVI and transpiration potential rates (0.66 and 1075 mm y−1), followed by double winter/summer crops (0.55 and 778 mm y−1) and single summer crop (0.45 and 679 mm y−1).
Website: http://www.arjonline.org/agricultural-sciences/american-research-journal-of-agriculture/
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