Population dynamics of Malus sylvestris stands in grazed and ungrazed seminatural grasslands and fragmented woodlands in Mols Bjerge, Denmark

Malus sylvestris (L.) Mill., is an important diversifying and structural element in seminatural grasslands in parts of temperate Europe. Awareness of this has been growing in recent decades. Little, however, appears to be known about the dispersal of the species in nature. The field study reported here suggests that large domestic herbivores may be a major vector of dispersal, as well as providers of suitable seedbeds for germination. Of the close to 1800 individual seedlings, the emergence and subsequent fates of which are recorded in this study, 98% have with certainty been spread through grazing by cattle or horses. The survival of the seedlings depends on a number of factors, e.g., the growth conditions due to the prevailing climate, light regimes at germination, nutrient availability, breaking of field-layer vegetation canopy and avoidance of excessive browsing. Some 20% of the seedlings may survive for longer periods if grazing ceases, while very few survive under continuous grazing. The study shows an inverse relationship between the survival rate and the grazing pressure in the early post-germination years, but it also indicates that germination density is directly related to grazing pressure. There appears to be a direct relationship between the stocking rate and level of grazing by cattle, indicating that Malus sylvestris may not be actively sought by the cattle for food. Accordingly, the survival expectancy of the seedlings is higher where grazing pressure is less and this may be used in a grazing strategy to establish or secure a population of Malus sylvestris by natural dispersal.