摘要：We studied weed seed bank composition in Azul, an agricultural region in the center of the Province of Buenos Aires, Argentina. Wheat is the most abundant crop of the region, whereas summer crops, such as corn, sunflower, and soybean, are less common. The study involved 20 sites corresponding to four types of geomorphological environments: watersheds (environment I), watershed slopes (environment II), secondary watersheds (environment III), and valleys (IV). At each site, a soil sample, composed of 20 random soil cores of 20 cm depth and 35 mm diameter, was obtained. Seed density was estimated by the germination technique. Environment I showed the highest seed density (more than 22000 seeds.m-2) and environment II showed the maximum species richness (about 10 species). Environment III, nevertheless, showed the largest variability of both seed density and richness. Considering the set of 20 sites, 33 species were detected in the seed bank. Approximately half of them were present in 20 to 70% of the sites. Annuals were widely represented (87.5 % of species), with a majority of cool-season species (69%). The five most frequent species (Polygonum aviculare, Viola arvensis, Digitaria sanguinalis, Ammi majus and Anagallis arvensis) were differentially associated with each environment, but all of them were more frequent in environment I. We hypothesize that edaphic limitations and topography of each environment would constrain decisions for crop rotations and management practices, indirectly affecting the seed bank
