The impact of forest spread on a marginal population of a protected peony (Paeonia officinalis L.): the importance of conserving the habitat mosaic

Abstract

In the Mediterranean region of Europe, land-use changes have allowed for rapid colonisation of open habitats by woody species. As a result, it is critical to gather information on how protected species in open habitats respond to forest spread in such areas. Our objective is to quantify whether spatial heterogeneity of the vegetation associated with recent forest closure influences demographic structure and maternal fertility in a population of the protected Paeonia officinalis L. In closed woodland, adult plants of P. officinalis are almost exclusively vegetative, in open habitats seedlings are rare and on the woodland edge there is a relative over-representation of flowering plants and seedlings. Forest closure dramatically reduces flowering frequency, but has no significant effect on maternal fertility of flowering plants. The spatial aggregation of seedlings close to the maternal plants suggests that dispersal is spatially restricted. Together, these results suggest that the viability of the population requires a transitional habitat between open garrigues or grassland with spaced trees and woodland. A management programme incorporating tree and shrub thinning and cutting of parcels in rotation to maximise the length of the forest edge could maintain a habitat mosaic that favours the persistence of this species in the study site.

The interplay of pollination, costs of reproduction and plant size in maternal fertility limitation in perennial Paeonia officinalis

“…Variation in seed production is more due to variation in habitat quality and its impact on biomass acquisition, since smaller plants Xower less often. Habitat closure also causes reduced Xowering and recruitment of seedlings in other populations of the study species (Andrieu et al 2007) and in other Paeonia species (Ne'eman 2003), and may make a strong contribution to reduced population growth (Silvertown et al 1993).…”

“…To verify the potential importance of these factors, we Wrst assessed whether the species is self-compatible and its capacity for spontaneous self-pollination in the absence of pollinators. Finally, since P. oYcinalis is a protected species whose populations are threatened by forest spread initiated by land-use changes that have occurred over the last century in Europe (Carmel and Kadmon 1999;Debussche et al 1999;Andrieu et al 2007), we tested whether maternal fertility is reduced in situations of forest closure, and the extent to which any reduced fertility is associated with habitat change is due to pollen limitation.…”

Living at the Edge: Local versus Positional Factors in the Long‐Term Population Dynamics of an Endangered Orchid

“…Global changes, and climatic warming in particular, are threatening factors that will have dramatic consequences for biodiversity. The negative effect that colonization of open habitats by woody species has on population demography of herbs (Lehtilä et al 2006; Andrieu et al 2007) can shift in some situations, such as the one we investigated here, and counteract range‐edge effects and other negative local factors. Forest expansion resulting from ongoing changes in the traditional land use of southern European countries has a negative effect on habitats of high diversity such as subalpine grasslands, but may also provide opportunities for species distributed mainly at higher latitudes.…”

How does herbivory affect individuals and populations of the perennial herb Paeonia officinalis?

“…Many of its populations are threatened by habitat closure (Andrieu et al, 2007a). This polycarpic plant has thick tuberized roots and individuals may live several decades.…”

“…Visits occurred in June and site visits followed a fixed order depending on peony phenology in each site (PSL, VIS, STF and TAU) in order to avoid any interannual bias due to differences in phenology among the four sites. Peonies were assigned to four demographic stages (pooled stages of Andrieu et al, 2007a): S = seedlings (a single leaf with leaflets not divided to the base; no stem), SV = small vegetative plants (a single leaf with leaflets divided to the base; no stem), LV = large vegetative plants (at least two leaves and a stem but no flower), and R = reproductive plants [with flower(s)]. Additionally, we surveyed stem number, number of leaves per stem, and the length and width of the largest leaf of each stem for each plant.…”