How can the minor species, Tectocepheus minor (Oribatida), dominate T-velatus in a no-tillage crop field?

Seasonal population dynamics and spatio-temporal distribution patterns of t he two Tectocepheus species were surveyed under a no-tillage field with two microhabitats, i. e. the conserved area (alleys) and the fertile but distu rbed area (rows). The density of T. minor was higher in the rows than in th e alleys from spring to summer, but lower in the rows from autumn to winter . The species had an aggregated distribution and the tendency was stronger in the rows than in the alleys. The density of T. velatus was higher in the rows than in the alleys in each season. The distribution pattern of the sp ecies changed between seasons and microenvironments, and the aggregated ten dency was less than that in T. minor. Analysis of the seasonal relation of environmental differences to the spatio-temporal dynamics showed that T. mi nor migrated between two microenvironments in response to seasonal environm ental changes. The species maintained a rather high density, while T. velat us tended to remain at one of the two microenvironments and maintained a mo derate density. The high abundance of T. minor could be caused by the effic ient use of two different microenvironments in the field.