Nitrogen-mineralization in dry tropical savanna: effects of burning and grazing

Abstract

The effects or burning and grazing on plant available nitrogen (NO₃-N + NH₄-N) and N-mineralization in a dry tropical savanna were examined. The plant available N ranged from 2.8 to 10.6 μg g⁻¹ with maximum values in the dry period (summer season) and minimum values in the wet period (rainy season). The trend for N-mineralization was opposite to that of the size of the available N pool. N-mineralization rates ranged from 1.8 to 30.6 μg g⁻¹ mo⁻¹ within an annual cycle. On average the pool of available N was 54% higher in the burned treatment and 48% higher in the grazed treatment compared to the protected treatment, similarly the mean annual N-mineralization was 20% higher in the burned and 16% higher in the grazed savanna.