Responses of epigeal beetles to the removal of weed cover crops in organic olive orchards

The study was conducted in an experimental organically managed olive orchard to test the short-term effects exerted on epigeal coleopteran populations by the removal of the plant cover (RPC) when compared to non-managed natural plant cover (NPC). The changes in abundance and diversity of beetles were analysed in three experimental blocks in which the cover crop was removed during the first week of June in 2005. Pitfall traps and coleopteran family level were a reliable approach to achieve the aim of this study. Related to soil conservation, maintenance of covers can potentially decrease soil erosion risk, and traditional soil practices tend to diminish diversity and activity of the soil fauna. This survey showed that abundance as well as family richness and domi-nance were greater in uncovered soils RPC compared to control covered soils NPC. Therefore, after a rainfall period, some cole-opteran families can be used as a quick assessment tool to evaluate effects of short-term disturbance (abiotic factor) on soil ar-thropod population. Beetle assemblage under vegetable cover seems to be more favourable. As a matter of fact weeds offer advan-tage (hospitable temperature and moisture) to beetles with respect to bare soils. Finally silvanids could be used as an indicator group of impact of agronomic practices applied to this soil in olive organic farming, since the removal of any kind of cover in olive orchards is an undesirable practice in terms of erosion protection and in terms of diversity conservation