Cumulative effects of 20 years of fire, grazing and selective tree cutting on soil water infiltration in sudanian savanna-woodland ecosystem of West Africa

Abstract

Structural and functional dynamics of savanna-woodland ecosystems are mainly shaped by fire, grazing and wood removal which effects depends both on their intensities. The long-term effects of those disturbances on key soil parameters are still largely unknown. We studied the cumulative effect of 20 years of early fire, grazing and selective tree cutting on soil water infiltration at two experimental sites with contrasting soil conditions (deep silty-clay versus shallow silty-sand) in the sudanian savanna-woodland ecosystems of Burkina Faso. Measurements were carried with a single ring infiltrometer at intervals of 5, 10, 20 and 30 minutes. Results showed that Grazing had negative effect at both sites (P<0.0001). Fire has no effect on infiltration rate at deep soil whereas it has a negative effect on shallow one. Selective wood cutting had beneficial effects for infitration rate at the site with shallow soil. Further, all combined effect of the diffreent treatment resulted in decrease infiltration rate as compared with the control (interaction exclosure, no cutting and no fire). The result suggested that projects which aim to manage or improve soil water properties must take in consideration occurrence of disturbances, soils type and avoid disturbance interaction mainly in shallow sandy soils.

Keywords: Disturbances, soil water properties, Burkina Faso, soil compaction, early fire, savanna ecosystem.