The effects of grassland management on plant performance and demography in the perennial herb Primula veris

1. Because of changing land-use practices and abandonment, many European calcareous grasslands are under increasing threat. In order to protect those grasslands that remain, better insights into how plant populations respond to different management scenarios are needed. 2. Using transition matrix models and life-table response experiment (LTRE) analysis, the effects of different management strategies (grazing, summer and autumn mowing, and no management) on plant performance and population dynamics of the perennial herb Primula veris (Primulaceae) were experimentally studied. Data were collected between 1999 and 2003 in a species-rich calcareous grassland. 3. Early grazing (May) resulted in low population growth rates (lambda < 0.860) and a mean annual population decline of 11%. Under these conditions, both the proportion of flowering individuals and flower and seed production per plant were low, resulting in seed limitation overall. However, when grazing started later in the growing season (early July) flowering probability and overall seed set increased, as did population growth rates (lambda > 1). 4. Mowing in autumn (October) was the most favourable management scenario (mean lambda= 1.213), resulting in high proportions of flowering individuals and a large seed output. Furthermore, this management yielded optimal conditions for recruitment and seedling establishment during the next growing season. 5. Summer mowing (mid-July) resulted in a similar increase of flowering and overall seed shed to autumn mowing, but recruitment rates were lower because of a dense and tall vegetation structure at the time of germination. Consequently, population growth rates (mean lambda= 1.045) were lower compared with the autumn mowing regime. 6. No management of the grassland resulted in low growth rates (lambda < 0.843) and a mean annual population decline of 35%, because of high mortality rates of each life stage and a lack of recruitment. Recruitment rates were strongly reduced by lowered flowering probabilities and limited germination possibilities. 7. Synthesis and applications. This study may enable conservation managers to understand better the effects of time and type of management on population dynamics of P. veris. In order to preserve the remaining populations of this long-lived species, management interventions can promote flowering and seed shed and reduce productivity of the vegetation by mowing in autumn. Finally, this study has clearly shown that the lack of any management, which is the fate of many abandoned calcareous grassland relicts, will seriously restrict the long-term survival of P. veris.