Composition and spatio-temporal variation of soil microarthropods in the biodiversity hotspot of northern Hengduan Mountains, China

The Hengduan Mountains, located on the eastern edge of the Qinghai-Tibetan Plateau, China, are considered to be a global biodiversity hotspot. The aims of this study were to analyze the composition and spatio-temporal distribution of the soil microarthropods in this area and the determinant factors. Six different habitats, including two deciduous broad-leaved forests, two coniferous forests, a coniferous and broad-leaved mixed forest and a subalpine meadow, were selected at elevations of 2659–3845 m. Soil microarthropods were extracted from soil samples collected from each habitat in April, August and November of 2008. The soil-microarthropod communities comprised at least 155 taxa and were dominated by Poduromorpha, Oribatida and Entomobryomorpha. The composition of the soil-microarthropod communities did not vary significantly among the six habitats, but the Acari were more abundant than Collembola in the deciduous broad-leaved forests and subalpine meadow, while the reverse was true in the coniferous forests and conifer-broad leaved mixed forests. Moreover, the diversity and abundance of soil-microarthropod communities varied insignificantly among habitats. However, significant seasonal variation was observed in the composition, abundance and diversity of the soil-microarthropod community in each habitat. The Shannon index was affected by elevation, while the taxonomic richness and Pielou index were sensitive to soil bulk density and C/P ratio, respectively. With regard to taxa, the habitats only had significant influences on the abundances of Poduromorpha, Entomobryomorpha and Mesostigmata, while the seasons had significant effects on the abundances of the all major taxonomic groups. The abundances of Poduromorpha and Entomobryomorpha were mainly affected by the plant species richness, but those of Prostigmata and Mesostigmata were only affected by elevation. The results demonstrate that soil microarthropods in the study area respond more actively to temporal changes than to habitat changes, and the deciduous broad-leaved forests and grassland meadow are more suitable habitats for Acari, while the coniferous-forest habitats are more favorable habitats for Collembola.