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.

The objective of the investigation was to determine the response of different taxa of mites across the land use types and demonstrate that soil mites could be used as an indicator of environmental change after the conversion of secondary forests into rubber plantations. The sampling was performed during the dry season on 12 sampling areas, consisting of four land use types: secondary forests, 7-year-old rubber plantations, 12-year-old rubber plantations, and 25-year-old rubber plantations, with three replications of each treatment. Soil cores were sampled along a 40 m transect with a steel corer. The soil mites were extracted using modified Berlese-Tullgren funnels during a 10 day period. Soil physico-chemical parameters were measured on each sampling area. The conversion of secondary forests into rubber plantations was characterized by a modification of the mean values of mite density (+103 and +262%), species richness (-11 and +32%), water content (-41 and -5%), bulk density (+6 and -3%) and soil organic carbon (-73 and -59%) respectively, after 7 and 25 years of conversion. The density of mites, species richness and soil water content increased with the aging of the rubber plantations, demonstrating an improvement in soil ecological quality and environmental conditions. These results are confirmed by the values of the Maturity Index of Gamasid mites, which increased with the increasing age of rubber plantations. In other words, the severity of environmental impact decreased with the aging of the rubber plantations and was ranked as follows: 25-year-old rubber plantations < secondary forest < 12-year-old rubber plantations < 7-year-old rubber plantations. The Maturity Indexes estimated that 25-year-old rubber plantations (0.84) and in secondary forests (0.74) are relatively similar and characterize stable habitats, which are potentially dominated by Gamasid species with K selection.

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.

The objective of the study conducted in the Lamto Guinean savannah situated at 165 km northwest of Abidjan, Côte d'Ivoire consisted to assess the changes in soil mite abundance, diversity and community structure specific to the second fire cycle applied in 2015, as well as the inter-annual variation between the two fire cycles (2014 and 2015). Three study sites (Salty marigot, Plateau and North piste) were selected in shrub savannah, where on each, three adjacent stands of 100 m x 50 m formerly delimited were considered. The three fire regimes (early, mid-season, and late fire) were respectively applied on the three sites and stands. Thus, 135 soil cores (5 soil cores × 3 sampling periods × 3 fire regimes or stands × 3 sites) were used for mite extraction. 108 soil cores were taken at two upper layers (0-5 and 5-10 cm) for determination of the bulk density and water content. Whatever the fire regimes, the mean density of soil mites decreased after the fire application. The highest value of density was observed through the early fire (1,715 ± 327 ind.m -2 ) whereas the lowest value was recorded during the mid season fire (1,433 ± 153 ind.m -2 ). 41 species had been recorded along the three fire regimes and distributed as follows: early fire 34 species, mid season fire 20 species , and late fire 13 species. The mean species richness of soil mites changed significantly across the fire regimes, and reduced after the fire application, except for the mid season fire. The Simpson diversity index was significantly modified across the fire regimes, and increased after the fire application. Beyond to 24 specialist species, over 50% of the species observed before the burns were rediscovery after the fire application, and could explain this variation. The inter-annual variation of soil mites showed that the density (early fire, mid season fire, and late fire), mite richness (early fire), and diversity (early fire and late fire) increased whereas the mite richness (mid season fire and late fire), and diversity (mid season fire) decreased, respe ctively, during 2015-burn compared to the previous cycle (2014-burn). The rebound of soil mite parameters during the second fire cycle could be assigned (i) to litter and woody debris, which burn in a mosaic, reflecting local fire intensity, (ii) improving of stand complexity and canopy structure, and (iii) fire tolerance of mites.