Impacts of different prescribed fire frequencies on selected soil chemical properties in a semi-arid savannah thornveld

Abstract

Effects of fire frequency on soil chemical properties in semi-arid savannahs are still unclear. A study was conducted on a long-term fire research trial in the semi-arid part of Eastern Cape Province, South Africa. The study aimed at determining the impact of outbreak on the soil properties by comparing the effect of different prescribed fire frequencies on pH, C, N, P, Ca, Mg, Cu, Zn, Mn, Na levels and C:N ratios. The treatments were no burn (control), sexennial, quadrennial, triennial, biennial and annual burns randomly laid in uniform blocks. A line intercept sampling technique was used in soil sampling from 0 to 75 mm depth for analysis. Fire burning frequencies had significantly varied effects on soil chemical properties (P < 0.05). There was an increase of C, Mg and Ca in the triennial than other frequency treatments. Significant positive correlations were observed between N and P, Ca and Mg and pH and Ca and Mg content and burning frequencies. C and other elements content were reduced in most burning frequencies except triennial. The triennial burning frequency may be an ideal option for veld management. Further studies under different climatic conditions, soil and vegetation types and fractionation analysis of chemical elements are necessary to determine whether different frequencies result in short-or long-term fire-induced changes.