Plant Species Diversity and Composition Differ Significantly Between the Boundaries of Kettle Holes and Field Borders

The boundaries around habitat islands in agricultural fields are rather unexamined, although they may be an important part of agroecosystems in some regions. In this study, we surveyed field boundaries in northeastern Brandenburg both at outer field borders and around kettle holes, which are typical habitat islands in the region. We examined, described, and compared the plant species diversity and composition at both the inner and outer field boundaries in the arable fields (crop edge) as well as in permanent vegetation (field margins). Diversity was assessed and compared with Hill diversity values, using the iNext framework. Non-metric multidimensional scaling and permutational analysis of variance were used to compare species composition at different field boundaries and to search for variables that drive species composition at the local scale. The results revealed that both species diversity and composition differed significantly between the inner and outer boundary along the crop edges and at the field margins. Local site conditions, namely a moisture gradient, influenced the species composition of the field margins, resulting in differences between the inner and outer field margins. Mitigated through crop growth and cover, the moisture gradient influenced also the species composition of the inner and outer crop edges, despite the management practices on the fields were the same.