Patterns of soil mite diversity in Lamto savannah (Côte d’Ivoire) submitted at different fire regimes

In this study, we evaluated the impact of different fire regimes (early, mid-season, or late fire) on soil mite abundance and diversity in three study sites (Salty marigot, Plateau and North piste) of the Lamto shrub savannah at 160 km northwest of Abidjan, Côte d’Ivoire. On each site, three adjacent plots of 100 m x 50 m were delimited, to which a given fire regime was applied. At each site, soil cores were taken at 0-10 cm soil depth three days before the fire application, the day after and one month after the fire (10 soil cores x 3 sampling periods x 3 fire regimes or plots x 3 sites = 270 soil cores). Soil mites were then extracted from these cores. 108 soil cores were sampled at two upper layers (0-5 and 5-10 cm) for estimation of the bulk density and water content. After data analysis, four groups of mite were observed (Actinedida, Gamasida, Oribatida and Acaridida). Gamasida and Oribatida were dominant groups (early fire: Gamasida 35%, Oribatida 55%; mid-season fire: Gamasida 16%, Oribatida 70%; late fire: Gamasida 16%, Oribatida 74%). In total, 70 species were observed, with 29, 44 and 31 species recorded respectively during the early, mid-season and late fires. Mite density and species richness varied significantly along the three fire regimes and decreased substantially after fire application. Except for the mid-season fire, Simpson index from all mites differed significantly across sampling periods. Lower Oribatida represented 25% of the total Oribatida. Whatever the fire regimes, brachypyline Oribatida abundance increased the day after fire application. Overall, fire intensity reduced drastically soil mite abundance and diversity.