Arable weed species associated with soil tillage systems under Mediterranean conditions

Tillage soil erosion is seen as a great problem in the Mediterranean region and is worsened by the climatic conditions. Previous studies have shown a decrease in biodiversity in arable lands across Europe. Weeds are a major component of biodiversity within agro-ecosystems, but few studies have aimed to associate weed species with soil tillage intensity. We performed an analysis to test the potential short-term effects of different tillage systems on weed species under our study conditions. The emerged weed data were measured, comparing a conventional tillage system with conservational tillage systems (minimum tillage and no tillage) in 2 cropping systems (monoculture wheat and a rotation scheme of barley–legume–wheat–fallow). Compared with the tilled soil, higher weed density and weed species richness were observed in the conservation tillage plots. The weed density and weed species richness in the monoculture system were higher compared with those in the crop rotation system. We used classification and regression trees to analyze the relationship between the soil tillage systems and the weed community, taking into account the climatic conditions. The results indicate that different soil tillage systems produced tree models: Silene vulgaris (L.) was associated with the MT system and high and irregularly distributed rainfall; Hypecoum imberbe Sm. and Hypecoum procumbens (L.) were linked to MT plots with low and well-distributed precipitation rates; and Cardaria draba (L.) was present all years independently of climatic conditions but was never found in the NT system, so its presence could be regarded as an indicator of tillage intensity.