Soil based assessment of the invasive species Vernonanthura phosphorica (Vell.) H. Rob. (Asteraceae) in Burma Valley, Zimbabwe

Abstract

Sites occupied by Vernonanthura phosphorica in Burma Valley, Zimbabwe tend to be species poor, with the invasive species dominating the flora. An investigation was carried out to establish soil conditions under which V. phosphorica, an invasive alien shrub, thrives. Five randomly selected sites under V. phosphorica invasion were compared to five adjacent sites unoccupied by the species. Plots measuring 20 m × 20 m were randomly placed within each site. Five 1 m × 1 m quadrats were systematically laid at the four corners and centre of each plot and sampled for soil nitrogen, phosphorus, carbon, pH and temperature. An independent t-test was used for the analysis of these variables. Results showed that the invaded sites had significantly higher soil nitrogen and phosphorus content and temperatures than sites unoccupied by the invasive species. Soil pH and carbon were significantly lower on invaded sites. The observed soil physical and chemical differences between each set of sites provided an insight into conditions under which the invasive species thrives. It was, therefore, concluded that the invasive V. phosphorica thrives under high soil temperature, nitrogen and phosphorus content and low soil pH and carbon.