Abstract

MAGLIANO, Patricio N. et al. Cambios en la partición de flujos de agua en el Chaco Árido al reemplazar bosques por pasturas. Ecol. austral [online]. 2016, vol.26, n.2, pp.95-106. ISSN 1667-782X.

Vegetation plays an important part in regulating water fuxes in ecosystems, specially in dry regions where a large fraction of precipitation is evapotranspirated. Here, we assessed how the replacement of native dry forests by pastures, with the aim of increasing livestock production, affects water fux partition in the Arid Chaco plains. We characterized the size and intensity distribution of precipitation events, and we measured canopy interception, runoff, deep drainage and potential evaporation in paired stands of dry forests and pastures in San Luis, Argentina. Pastures presented lower canopy interception (0.35±0.13 vs. 1.51±0.50 mm/precipitation event), higher runoff (~28 vs. 0% runoff in large and intense precipitation events) and higher potential evaporation (7.0±0.9 vs. 4.4±0.9 mm/day in summer). Deep drainage was nil in both cover types, but a 2 m downward salt displacement was found under pastures. After each precipitation event, soil moisture horizontal distribution was more homogenous in pastures, as a result of less canopy and soil-surface water redistribution at the patch scale. Our results suggest that the establishment of pastures in sites previously covered by forests would reduce the proportion of precipitation potentially transpired by vegetation and increase the potential risk of water erosion. We highlight the need for a better understanding of water dynamics at the patch scale in these plain landscapes, due to the relevance that water redistribution processes have in explaining water balance and the ecohydrology of the system.

Keywords : Water balance; Dry Chaco; Clearing; Intensifcation; Extensive livestock production; Land use/land cover change.