Reintroduction of rare arable plants: seed production, soil seed banks, and dispersal 3years after sowing

Diversity of arable plants in Europe has markedly declined during the past decades and many species have become threatened. Low-intensity farming can offer potential retreats for these species, while spontaneous dispersal between such fields is unlikely. Thus, reintroduction of endangered species is necessary to restore agrobiodiversity. To test the applicability under real farm conditions, we seeded a mixture of three winter annuals (Legousia speculum-veneris, Consolida regalis, Lithospermum arvense) at 850 seeds/m(2) on four organic farms near Munich, Germany, in autumn 2011. Seed production and soil seed banks were investigated on four plots within one field on each farm for 3years. In addition, we evaluated seed dispersal caused by arable management along the main machining direction. In the first year, winter cereals were cultivated and the study species emerged at all sites with a seed production mostly exceeding the initial sowing rates. In the third year, species establishment varied depending on crop rotations. Seed production of L. speculum-veneris was higher than in the two other species, and exceeded the number of originally sown seeds up to 20 times. While L. speculum-veneris became very common in the seed bank, C. regalis was less abundant and L. arvense hardly developed a soil seed bank. Seeds of L. speculum-veneris and L. arvense were found up to 15m and seeds of C. regalis up to 13m away from the sown plots. We suggest using seed production, seed bank, and dispersal as key indicators to evaluate establishment of reintroduced arable plants.