Comparison of the vegetation and seedbanks of soybean fields, adjacent boundaries, and hedgerows in Ontario

Patterns of plant assemblages in habitats located within agroecosystems are poorly understood. A study of the seedbank and standing vegetation in 10 soybean [Glycine max (L.) Merr.] fields, their adjacent boundaries, and adjoining woody hedgerows was undertaken in Ontario. The objective was to examine the composition of plants of conservation value and weedy species in these habitats. The seedbank of each habitat was determined from soil cores in quadrats located at regular intervals along transects, using the seedling emergence method in the greenhouse. The vegetation was surveyed in plots adjacent to the seedbank sampling areas. There was no significant difference in total species richness of vegetation or the seedbank among habitat types. However, there was a marked difference in species composition. In the seedbank, no difference in weed species richness among habitats was observed. In vegetation, however, fields harboured significantly more weedy species than adjacent boundaries and hedgerows. The dissimilarity between the seedbank and the vegetation was confirmed in detrended correspondence analyses, which showed that hedgerow vegetation, and to a lesser extent boundary vegetation, differed from field vegetation and all the habitats of the seedbank. The analysis of soil properties indicated that organic matter and nutrient levels were often higher in hedgerows than in fields. It can be concluded that hedgerows are valuable habitats for plant diversity and that weed species represent a minor component of their overall vegetation composition.