Seasonal changes of soil microarthropod populations in microhabitats of oil palm plantations of Southern Sumatra (ABS Funds)

Due to being heavily managed, oil palm plantations are distinctively structured ecosystems featuring low amounts of undergrowth vegetation and thin organic layers, with only small-scale palm frond litter accumulations to provide habitat structure for litter-dwelling soil animals. The soil habitat in oil palm plantations is, therefore, likely to be weakly buffered against seasonal climatic changes. This study investigated variation in soil microarthropod communities and functional properties of the soil habitat (microbial biomass, organic matter, etc.) as affected by seasonal abiotic changes (e.g., precipitation, soil temperature, soil moisture). Additionally the role of microhabitats as refuges for soil animals during climatic extremes was investigated. Four oil palm plantations in the Harapan landscape were investigated. Soil samples were taken every 30 days during a period of 12 months and soil animals were extracted using modified Kempson extractors. Soil microarthopods from various microhabitats (e.g., shaded area, frond litter accumulation, detritus and epiphytes) were sampled once during the wet season and once during the dry season. Abundances of all soil animals were counted, and the Collembola and Oribatida were identified to family level. Preliminary results showed that, generally, abundance and family-level richness of oribatida were lower in open areas than in compost lanes of oil palm plantations, especially during the wet season. Populations of soil microarthropods (Collembola and Oribatida) were more abundant in microhabitats with high litter accumulation, such as stems, fronds and epiphytes compared to the open areas of oil palm plantations. This was more pronounced during climatic extremes, such as in the peak of the wet season. Therefore, enhancement of soil communities through soil animal enrichment in the open areas of oil palm plantations should be taken into account. Soil animal enrichment can possibly be done through addition of soil-animal-rich soils from the compost lanes into the open areas of oil palm plantations.