Enhanced infiltration by trees in floodable cattle ranches in Paraguay

Periodic flooding limits livestock farming on cattle ranches in floodable areas. In order to propose recommendations for sustainable management of these ranches, we examined the relationships between surface water hydrological processes (infiltration and evaporation) and vegetation cover in the Paraguayan Humid Chaco. A total of 24 evaporation and infiltration measurements were made in a gradient of woody vegetation density between the forest and the adjacent grassland, and at different distances from reference trees (from the trunk to outside the tree crown). Soil texture and moisture were also characterized. There was a positive effect of woody vegetation density on infiltration although final infiltration rates in forests (94.5 mm h − 1 ) were not significantly higher than in grasslands (22.0 mm h − 1 ) or forest-grassland transition (11.5 mm h − 1 ). Evaporation was significantly lower in forests (0.0338 mm h − 1 ) than in grassland (0.1361 mm h − 1 ) or at the transition zone (0.0868 mm h − 1 ), reflecting the effects of tree cover on microhabitat features. Infiltration rates decreased with the distance to the tree trunk. These results support our hypothesis that subtropical forests, specifically Schinopsis balansae and Psidium sp., have a positive effect on infiltration, and these forests have a negative effect on surface water evaporation. Introduction of trees at relative low densities in deforested rangelands may help improve hydrological services (i.e., enhance soil infiltrability) and facilitate cattle raising, while promoting local biodiversity.