Landscape and land-use effects on weed flora in Mediterranean cereal fields

Land-use intensity and landscape complexity could potentially affect weed flora of agroecosystems, by means of changes in species richness and composition. However, previous results indicate diverging patterns. This paper evaluates the relative importance of both factors on weed species richness and weed community composition within cereal fields in Catalonia (NE Spain). The percentage of arable land plus that occupied by human settlements within a circular sector of 1 km radius was used as a surrogate for landscape complexity and the amount of nitrogen inputs for land-use intensity. The seedbank, which could reflect the long-term effects of the agricultural intensification, and the emerged vegetation with and without weed control were surveyed to obtain comparable assessments of the weed flora, taking into account differences caused by weed control effectiveness. Intensive management induced changes in the emerged weed flora and caused a decline in species richness. Moreover, in the long-term (seedbank), it has also led to a certain level of weed loss. Conversely, landscape complexity had little effect on the seedbanks and emerged flora of cereal fields. Consequently, weed conservation policies in Mediterranean cereal fields should focus on farming practices and need not take account of the surrounding landscape.