Effect of the plant protection systems on soil arthropods in olive grovesfrom Alentejo region (southeastern Portugal)

Abstract: Changes in arthropod abundance and biodiversity can be associated with the changesin land use and agricultural practices. The aims of this work were: i) to study the abundance anddiversity of edaphic arthropods in olive groves following different plant protection systems(organic growing, intensive, super-intensive and conventional), ii) to analyse the seasonalvariation of the most abundant groups and iii) to evaluate the differences among groves. The fieldwork was carried out in Alentejo region (southeastern Portugal) and occurred monthly from Aprilto October 2010. In each grove, 25 pitfall traps with 7cm height and 6cm diameter wererandomly placed at the soil level and collected after 24h. Traps were placed in the south side ofthe canopy at 50cm from each tree trunk. All trapped individuals were preserved in 70% ethanol,sorted and identified to class, order or family taxa. Principal Response Curves (PRC) method wasused to analyse the effect of management regime at the community level. Significantly higherabundances of arthropods were registered in the organic grove when compared with the otherthree systems. Formicidae was the most abundant group in all the sampled groves reachinghigher abundances in August in the super-intensive system while the other three systems obtainedhigher abundance of Formicidae in May. Considering Araneae, this group was more abundant inJune in the organic and super-intensive systems and in October in the conventional and intensivesystems. Coleoptera were more abundant in October in the organic and intensive systems, in Mayin the super-intensive and in April in the conventional system. According the PRC method,Formicidae and Diptera were the most affected groups by the plant protection system. Moreover,in the sampling period, the super-intensive system showed the highest negative impact overarthropod abundance which can be explained by the application of herbicides for the control ofConyza canadensis.