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 measured by pitfall trapping in a small fallow field. The field was divided into 5 x 5 m plots either covered by a naturally established weed stand (control) or mowed and superficially cultivated (bare ground). Daily operated pitfall traps were placed in the centres of both kinds of plots. Weather and seasonal variation of species abundance were dominant 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 greater in controls than on bare ground, while phytophagans showed less preference. The preference for the shaded control stand was well expressed at air temperatures of 18–25°C while at low temperatures of < 16°C the catches on shaded and bare ground surface were similar. The preference for the control stand was positively correlated with species body size.