The role of olive trees in rainfall erosivity and runoff and sediment yield in the soil beneath

摘要

The modification of raindrops by the canopy of olive treesincreases the kinetic energy of the rain per unit area. The kinetic energycomputed from the measured drop size distribution under the tree canopy insimulated rainfall experiments is greater than that received in the open, 17.1 J mm-1, as against 15.7 J mm-1 . This causes higher soildetachment and loss than that observed outside the canopy. Tillage treatments ofthe soil modify its erodibility, accelerate soil detachment and reduce,simultaneously, the velocity of runoff. Both effects reduce the amount ofsediment compared to that observed in the non-tilled soil. The average values ofsoil lost per unit of rain depth and unit area were 5.81 g mm-1 m-2(conventional tillage) and 4.02 g mm-1 m-2 (zero tillage)under the canopy compared to 0.89 g mm-1 m-2 (conventionaltillage) and 0.95 g mm-1 m-2 (zero tillage) in the open.