SOIL-MOISTURE CHANGES UNDER SHRUB COVER (ROSMARINUS-OFFICINALIS) AND CLEARED SHRUB AS RESPONSE TO PRECIPITATION IN A SEMIARID ENVIRONMENT -STEMFLOW EFFECTS

Variations in soil moisture after rainfall under Rosmarinus officinali s L. and cleared shrub (prior cover R. officinalis) were analyzed. The results from the General Linear Model analysis showed the relevance o f shrub plant cover on soil water infiltration in depth. A threshold o f about 15-18 mm of rainfall was established, above which soil moistur e changes tended to be positive. Moisture variations showed no differe nces at 15 cm depth with precipitation events of more than 18 mm, and were higher than those occurring at 30 cm depth (p < 0.05). Moisture c hanges after precipitation were not significantly different between cl eared shrubs and soil covered by vegetation at 15 cm depth (p > 0.05), although there were significant differences at 30 cm depth (p < 0.05) and remoistening was greater in soils under vegetation than in cleare d shrubs. Moisture variations had a negative average in <15 mm rainfal l at 15 and 30 cm, and were only dependent on precipitation. A gradati on in moisture changes among depths was not significant (p > 0.05); th e highest variations occurred at 15 cm, and the smallest at 50 cm. The effect of stemflow rechanneling observed in simulated rainfall in R. officinalis shrub species is discussed.