THE EFFECT OF PLANT COVER AND WEATHER ON THE ACTIVITY DENSITY OF GROUND SURFACE ARTHROPODS IN A FALLOW FIELD

In 1992-1994, the activity density of ground surface arthropods was me asured by pitfall trapping in a small fallow field. The field was divi ded into 5 x 5 m plots either covered by a naturally established weed stand (control) or mowed and superficially cultivated (bare ground). D aily operated pitfall traps were placed in the centres of both kinds o f plots. Weather and seasonal variation of species abundance were domi nant factors of changes in abundance and diversity of arthropods. Many species preferred weedy control stands, a few preferred bare ground, or showed little preference. Overall abundance of predators was greate r in controls than on bare ground, while phytophagans showed less pref erence. The preference for the shaded control stand was well expressed at air temperatures of 18-25 degrees C while at low temperatures of < 16 degrees C the catches on shaded and bare ground surface were simil ar. The preference for the control stand was positively correlated wit h species body size.