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 officinalis L. and cleared shrub (prior cover R. officinalis) were analyzed. The results from the General Linear Model analysis showed the relevance of shrub plant cover on soil water infiltration in depth. A threshold of about 15-18 mm of rainfall was established, above which soil moisture changes tended to be positive. Moisture variations showed no differences 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 changes after precipitation were not significantly different between cleared 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 cleared shrubs. Moisture variations had a negative average in <15 mm rainfall at 15 and 30 cm, and were only dependent on precipitation. A gradation in moisture changes among depths was not significant (p > 0.05); the 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.