Shadow Effect in the Redistribution of the Infiltration in a Semiarid Zone

The plateu of Mexico, besides presenting an arid and semiarid climate, have suffered the loss of vegetation caused by important land use changes in the last decades. The dominating vegetation is constituted by huizache (acacia farnesiana) and mezquite (prosopis laevigata). In the present study, the importance of trees in the redistribution of the infiltration was investigated. Carried out measurements under and around two trees, the soils characteristics were determined in laboratory, and infiltration tests were conducted: a) simple ring (Beerkan) and b) minidisc (MDI) infiltrometer. The tests were carried out by 2 huizaches at different distances and directions from trunk. Taking as a base the infiltration time of the test close to the trunk, the infiltration timing at: 1.5, 2.5, 3.5, 4, 4.5, 5 and 6 m. of distances, showed a 1:1.20, 1:1.40, 1:0.50, 1:0.60, 1:0.70, 1:0.80 and 1:1.20 relation between infiltration times, respectively. Such relationships indicate that the infiltration does not lineally decrease as theoretically expected. Additionally, the results indicated that around of the trees emerges a buffer zone that increase the infiltration (3.0-4.0 m), reaching the highest at 3.5 m. This behavior suggests that the shadow effect of the rain interception could influence in the redistribution of the infiltration. In conclusion, it may be commented the fact that native vegetation preservation is vital to rise the infiltration and improve the water resources management in semiarid zones.