Is the grass always greener on the other side of the fence? Primula veris L. as an example of plant survival at different management intensites

摘要

The large number of threatened species, both animals and plants, in the European agricultural landscape has often been attributed to the abandonment of semi-natural grasslands. Species may, however, also be threatened in the remaining managed grasslands due to a changed and intensified management. In this study, effects of grazing management and population characteristics were examined in terms of their importance for the seed poduction and recruitment of the perennial herb Primula veris L. (cowslip). Four different life-cycle events related to reproduction were studied in around 30 populations, in 2003 and 2004. in an 11 km2 landscape in Sweden, and related, to a number'of habitat and. landscape properties. Population structure was examined in 11 populations in 2004. The loss ofpropagul.es in total and at each life-cycle transition was calculated. The results show that high proportions of propagules were lost due to grazing, unsuccessful pollination, and unsuccessful establishment of seedlings. Nosingle explanatory variable could, unambiguously explain unsuccessful pollination in both years. Grazed populations had, compared to ungrazed, on average lower seed set, higher seedling per seed ratio but equal density of seedlings, lower density of vegetative plants, and equal density of juvenile plants. Equal seedling density indicates that reduced seedling recruitment per seed in ungrazed grasslands was compensated by a higher production of seeds, and. conversely, the loss of seeds by grazing in grazed areas was compensated by--higher seedling recruitment per seed. The results from this study add to the increasing number of studies which indicate that low-intensity and site-specific grazing regimes have to be included in the management of semi-natural grasslands to maintain or enhance the diversity of plants and the diversity of organisms depending on the vegetation.