Landslide Effect on an Oribatid-Mite Community in a Monsoon Forest

Landslide-caused erosion of soil alters above ground plant cover and primary production, and is a major disturbance in forests and agro ecosystems in Taiwan. Bimonthly litter collections were conducted for one year, with oribatid mites studied at landslide sites and on the undisturbed forest floor. We hypothesized that landslide soil erosion would decrease oribatid-mite abundance and diversity and alter its community structure compared with control site. Eighty-three oribatid morphospecies belonging to 47 families were sampled, with higher density of oribatid mites in the landslide site, and clear correlation with rainfall. In landslide areas, the density of total adult and juvenile oribatid mites was significantly higher in the wet than dry season. Contradictory to our hypothesis, the diversity of oribatid-mite morphospecies was not significantly different between seasons and sampling sites. Density of Peloribates sp. and Scheloribates sp. was dominant in both sampling sites and seasons. Density of Peloribates sp. in the control sites was 2.9- and 2.3- fold higher than in landslide sites in dry and wet seasons, respectively. Density of Scheloribates sp. was 2.8- and 4.6- fold higher in the landslide than control site in dry and wet seasons, respectively. The exact mechanisms controlling oribatid-mite community structure were not yet determined, but a predictable trend was found for the effects of rainfall and landslide soil erosion on total oribatid-mite density and morphospecies number. A natural process such as a landslide is known to have a devastating effect on the aboveground community, but for the belowground soil biota, it could trigger new trophic organization.