Establishment of Rhinanthus angustifolius in a successional hayfield after seed dispersal by mowing machinery

The role of seed dispersal by mowing machinery in the invasion into a hayfield under restoration management was investigated for the annual hemiparasite Rhinanthus angustifolius (C.C. Gmelin). Therefore, all plants of R. angustifolius in a hayfield were removed before seed production in 1994. As R. angustifolius seeds rarely survive for more than 1 year this would almost entirely prevent establishment of seedlings in 1995. In August 1994 the hayfield was divided into three parts. Under fair-weather conditions two of these parts were mown by a clean tractor disk mower combination and a tractor disk mower combination previously contaminated with R. angustifolius seeds, respectively. The third part was mown under rainy conditions by a contaminated caterpillar mower. In June 1995 all established R. angustifolius plants within the three parts were mapped. In both parts mown by contaminated machinery more plants of R. angustifolius were found as compared to the part mown with clean machinery. The part mown under wet-weather conditions by the caterpillar mower, in particular, contained many established plants of R. angustifolius. The results suggest that spatial patterns of establishment are induced by machinery. The conclusion of the experiment is that mowing machinery acted as a dispersal agent of R. angustifolius seeds in 1994. This probably applies to other hayfield species as well. Machinery may therefore play a major role in seed dispersal within the nature reserve, enhancing the speed of succession within hayfields. The circumstances under which the experiment took place did not allow us to conclude on separate effects of machinery type or weather conditions on seed dispersal. However, both effects may exist.