Early-Season Effects of Wildfire on Soil Nutrients and Weed Diversity in Two Plantations

Abstract This study assessed early-season effects of spontaneous wildfires on soil fertility and weed diversity in two managed plantations – cashew and teak – in Ilorin, Nigeria. Soil pH and nutrients in the topsoils and subsoils of burned and unburned plantations plots after a spontaneous wildfire were analysed. Species diversity and similarity were determined based on the composition and abundances of weed flora two months post-fire. The fire effects on soil nutrients and weed composition in the plantations were evaluated using the canonical correspondence analysis. Burns incidence significantly improved the organic carbon, organic matter, and Ca contents while reducing total N and Mg in both plantations. Twenty-eight weed species were distributed in 9 angiosperm families. Fire differently affected weed composition, abundance and diversity in the plantations. Burning improved soil organic carbon and organic matter contents and restricted Tephrosia bracteolata, Desmodium tortuosum, Daniellia oliveri, Senna obtusifolia and Zornia latifolia to the burned cashew plantation. The occurrence of Euphorbia heterophylla, Eriosema psoraleoides and Crotalaria retusa in the burned teak plantation was associated with a direct fire effect on soil Na and Ca contents. Burning influenced soil nutrients in the studied plantations, but weed diversity increased in the teak plantation and was reduced in the cashew plantation.