Azul, in the center of the Province of Buenos Aires (Argentina), includes flat environments in the north and hill environments in the south. Last constitutes a predominantly agricultural area where the wheat crop, principal activity, alternates with summer crops as corn, sunflower and soybean. The objetive of the present paper is to characterize the weed seed bank of such area in a global way. The whole rank of seed density and the relative abundance distribution and spatial design of species were analyzed. The basic information was obtained applying the germination technique to soil samples corresponding to 20 sites on a regional transect of 14 km. The seed density rank for the study area was 1173-44000 seeds/m2, and 33 species were recorded. Digitaria sanguinalis is the predominant species with 43 % of the seed bank, followed by Polygonum aviculare with 15 %. Both species together with Anagallis arvensis and Setaria viridis constitute the 70 % of the seed bank. The spatial distribution of species along the transect showed a variable aggregation degree, recording a significant positive correlation between the contribution to seed bank and the variance/mean ratio. This correlation demostrates that the most abundant species show a greater spatial variation, although different distribution patterns were observed.
Seed; weed; relative abundances; spatial distribution