Resembling patterns of weed diversity in maize fields of Brittany (France) and the Rolling Pampa (Argentina).

POGGIO, SANTIAGO L; BAUDRY, JACQUES

Kaposvár

Congreso; 15th European Weed Research Society Symposium; 2010

European Weed Research Society

Field edges usually harbor more species than the cropped area that they delimit. The distribution pattern of arable plants in field edges is strongly affected by the agricultural management and the heterogeneity of the surrounding farmland mosaic. To test this hypothesis, weed species occurring in both edges and the core area of fields cultivated with maize have been surveyed in Pleine-Fougères (Brittany, France), and afterward compared with similar surveys previously obtained in Rojas (Rolling Pampa, Argentina). Brittany farmland has smaller fields usually delimited by an intricate network of woody hedgerows. Pampean farmland is more homogeneous due to larger fields and sparser networks of wire-fencerows. We here define field edge as the 8 m strip of the cropped area neighboring with the non-cropped boundary strip that set the limit with the adjacent field. Weed species richness was additively partitioned into alfa, beta, and gamma diversity components, calculating beta diversity as the difference between gamma diversity and mean alpha diversity. Total species richness was 59 and 51 in Pleine-Fougères and Rojas, respectively. The gamma diversity of field edges was greater than in the core of fields in both sites, whereas mean a-diversity of field edges was only higher in Rojas. Mean alpha diversity did not differ between sites (P = 0.319), while the effect of field habitat was marginal (P = 0.063). Site and field habitat effects on beta diversity were highly significant (P < 0.0001), but there was no significant interaction between both factors (P = 0.504). Average beta diversity differed between sites (Brittany: 34.5; Rolling Pampa: 21.2) and field habitats (field edge: 32.2; field core: 23.5). Interestingly, beta diversity of both field cores in Brittany (29.6) and field edges in the Pampas (25.0) did not differ. Our results confirm previous findings in Western Europe that beta diversity reflects the turnover of weed species among fields due to the greater heterogeneity of surrounding landscapes. Moreover, our results also suggest that the weed richness of field edges in both sites would be maintained through apparent dispersal from non-cropped field margins. More importantly, our findings extend current evidence by having compared weed assemblages from the well-known Armorican landscapes with those from the homogeneous and extensive landscapes distinguishing the Pampas of Argentina.