Abundance and diversity of soil mite (Acari) communities after conversion of tropical secondary forest into rubber plantations in Grand-Lahou, Cote d'Ivoire

The objective of this investigation was to understand the modification of mite communities and soil physico-chemical parameters after conversion of secondary forests into rubber plantations and how these change with the aging of the plantations. The sampling was performed in a humid period and samples were taken from three of each age of secondary forests, 7-year-old rubber plantations, 12-year-old rubber plantations and 25-year-old rubber plantations. We hypothesized that the stress imposed on mite communities during site preparation and planting would be compensated for by the reduction of the soil degradation index as the rubber plantations age. Across the 12 sampling areas, 120 soil cores were taken at 10 cm soil depth over a 40 m transect. Soil physico-chemical parameters were characterized and soil mites were extracted with a modified Berlese-Tullgren funnel over the course of 10 days. The results showed that conversion of secondary forests into rubber plantations leads to a modification in the density of mites (-60 and +1%), species richness (-48 and -15%), water content (-62 and -31%), soil organic carbon (-67 and -51%) and total nitrogen (-64 and -52%) respectively after about 7 and 25 years of conversion. The investigation pointed out an improvement in soil ecological quality with the aging of rubber plantations over time and this was characterized by an increase in the density of mites (+150%), species richness (+63%), water content (+84%), organic carbon (+50%) and total nitrogen (+33%) in the 25-year-old plantations compared to the 7-year-old plantations.