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The impact of fire frequency on selected soil physical properties in a semi-arid savannah Thornveld

Magomani, M. I., van Tol, J. J.
Acta agriculturæ Scandinavica 2019 v.69 no.1 pp. 43-51
aggregate stability, bulk density, burning, environmental factors, fire frequency, organic carbon, range management, sampling, savannas, soil sampling, soil water, texture, water repellent soils
The use of fire in rangeland management is standard practice, but the impact of fire frequency on soil physical properties is still not properly understood. In this study, the effect of fire frequency on selected physical properties was studied in a long-term burning experiment. Treatments included: no burn (control), sexennial, quadrennial, triennial, biennial and annual burns. A line intercept sampling technique was used to collect disturbed and undisturbed soil samples from the surface for analysis. Frequent burning significantly increased the aggregate stability and bulk density when compared to less frequent burning. Frequent burning resulted in lower hydraulic conductivities and water conducting macroporosity when compared to intermediate burning frequencies, likely due to lower organic carbon contents associated with frequent burning. Soil water repellency was the highest in quadrennial burned plots. The results indicate that frequent burning can have a detrimental impact on soil physical properties, but small variations in inherent soil properties (texture) have a more dominant effect on the physical properties than fire frequency management. The results emphasize the complexity related the effect of fire on soil properties and future work should include all environmental factors in order to derive sustainable burning frequencies for this site.