Spatial and temporal patterns of weed invasions: Implications for weed management and crop yield

Invasion, establishment and extinction of the: spontaneous vegetation in the agricultural land of the Rolling Pampas, Argentina,was studied in different space and time scales. At regional scale, the successional process occurs independently of the agricultural practices carried by the farmers. Soil deterioration caused by tillage practices and agricultural history only affect a small proportion of the weed nora. Harvesting practices and herbicides affect abundance of weeds at patch scale and during a short period of time. The most important weed species in relation to their impact on crop yield, continue to gain importance in spite of the heavy load of herbicides and of other control procedures used by the farmers to get rid of them Unfortunately we know very little about the factors governing changes in plant species at different scales in the agro-ecosystem, specially concerning temporal dynamics.