Impact of wildfires on browse availability in the semi-arid thornveld of South-eastern Zimbabwe

The study aimed at investigating the impact of wild fires on browse availability on a thornveld vegetation community through assessing its effect on woody plant structure and composition. Data was collected from four randomly selected paddocks at Mahiye; a thornveld farm affected by annual wildfire outbreaks since 2000. A Point Centre Quarter technique on a line transects was used to collect the data. The records collected from the nearest woody plant (? 0.3 m) in each quarter included the woody species name, circumference at 30 cm height from the ground and distance from the point to that woody plant. Fifteen woody plant species were present in the study area dominated by the Acacia species. Out of the six hundred sampled woody plants, Acacia nilotica contributed 65%, Acacia karoo 10.8% and Acacia robusta 10.7% with the remainder contributed by the other twelve species. A Kruskal-Wallis non-parametric test could not provides sufficient evidence to prove that the woody plant community structure was homogenous. The height and the diameter structure had a significant variation (P < 0.05). This mighty be due to the presence of tall and large woody plants (height < 6m and diameter < 12 cm) within the community. Nevertheless, the Lorenz curves depicted less inequality in the height and diameter distribution within the farm (Gini coefficient 0.242 and 0.266 respectively) indicating dominance of a cohort. The histogram showed that more than 75% of the recorded stems were taller than 2.4 m and had a diameter > 8 cm. Apparent from the results, the plant community had high quality browse species but the dominant size compromised accessibility of the browse. Therefore, frequent wildfires reduced browse availability in thornveld rangelands. But further research is required to unveil the amount of unavailable browse.