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

Abstract

Summary 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 ( λ < 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 ( λ > 1). 4. Mowing in autumn (October) was the most favourable management scenario (mean λ = 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 λ = 1·045) were lower compared with the autumn mowing regime. 6. No management of the grassland resulted in low growth rates ( λ < 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 .

Effects of management regimes and extreme climatic events on plant population viability in Eryngium alpinum

“…3). In addition to affecting survival, grazing can have direct effects on fecundity: grazing can reduce fecundity rates by lowering seed set (Brys et al, 2004;Lennartsson and Oostermeijer, 2001), but can also increase fecundity by creating favorable conditions for seedling establishment, through the prevention of litter accumulation and the creation of gaps (Lennartsson and Oostermeijer, 2001 ). However, fecundity rates in BOU were the smallest of all sites and were the parameters contributing the most to the reduction in λ.…”

“…Current management strategies in Alpine ecosystems still include seasonal mowing or grazing, but with varying frequency, intensity and timing, and absence of management is also common. These new management regimes can lead to changes in plant community structure (Jantunen et al, 2007;Stammel et al, 2003) and to an increase of extinction risk for the most vulnerable species (Brys et al, 2004;Jantunen et al, 2007;Lennartsson and Oostermeijer, 2001;Marage et al, 2008). Populations can exhibit different vital rates and population growth rates between sites subject to different management strategies and characterized by variable ecological conditions.…”

Combining Historical and Ecological Knowledge to Optimise Biodiversity Conservation in Semi-Natural Grasslands

“…An early onset of grazing (April, May) and which continues throughout the season restricts flowering and seed production of vascular plants (Brys et al, 2004;Lennartsson & Oostermeijer, 2001). The seeds of the majority of grassland plant species ripen between late July to mid August (Dahlström et al, 2008;Wissman, 2006).…”

Effects of sheep grazing and temporal variability on population dynamics of the clonal herb Geranium sylvaticum in an alpine habitat

“…Vertebrate grazers seem, e.g., to prefer large ramets over small (Ehrlén 1995a), and grazing can reduce survival (Ehrlén 1995a), growth (Lennartsson and Oostermeijer 2001) and seed production (Bastrenta 1991;Knight 2004) of individual plants. At the same time, the grazers can facilitate seedling recruitment (Lennartsson and Oostermeijer 2001) and increased survival of juvenile plants (Brys et al 2004;Ehrlén et al 2005) through prevention of litter accumulation and creation of vegetation gaps. In order to evaluate population-level consequences of grazing, grazing effects need to be assessed for all stages in the lifecycle.…”