Life history variation in Cirsium palustre and its consequences for the population demography in vegetation succesion

Abstract

The objective of the study was to describe the life-history pattern of the biennial species <em>Cirsium palustre</em>. It has been demonstrated that under optimum conditions in the greenhouse individuals live 1.5 to 2 years, in a mown meadow 2 to 3 years, and during the plant succession in abandoned meadows they prolong their life to several years. This is accompanied by a gradual decrease of <em>C. palustre</em> population size. A relationship between the life-history pattern differences during a plant succession and the population abundance dynamics has been found. Reproductive-phase age is correlated with the rosette size. In spite of the occurrence of many limiting factors during a succession (closed plant cover, shading by macroforbs, willows) <em>C. palustre</em> survives until the formation of forest communities. Its persistence is favoured by: protracted life history, attainment the reproductive phase at different ages (not only in the second year), formation of a permanent seed bank, air-borne seeds and the emergence and survival of seedlings under the canopy of several-year old rosettes during a strong competition. The arresting of juvenile individuals under the rosettes for several years has been termed the "rosette mechanism". <em>Cirsium palustre</em> can be included among facultative biennials. In every conditions a proportion of individuals in a population attain the flowering phase in life year 2. During a succession the proportions of "triennial" and "quadriennial" forms, and at the terminal stage - of perennial monocarpic forms increase

Impact of the biocontrol beetle, Cassida rubiginosa, on the secondary weed target, marsh thistle (Cirsium palustre)

“…50 to 60%, as imposed here experimentally) might not reduce the performance of a large rosette or bolting plant, it could affect smaller plant size classes. Marsh thistle is a facultative biennial: some individuals grow as a strict biennial, and reproduce in their second year, following a vernalisation period as a vegetative rosette; but many individuals remain in the vegetative state for three to five years before obtaining sufficient size to bolt and produce seeds (Ballegaard & Warncke 1985;Falińska 1997). The probability of transitioning to the reproductive stage increases sharply for rosettes over 20 cm in diameter and, at 40 cm, bolting is a near certainty.…”

“…Ultimately, C. rubiginosa will need to reduce seed output in order to cause population level declines of marsh thistle, or other secondary thistle weeds. This could be achieved by reducing the survivorship of rosettes, delaying the transition to the reproductive stage, or reducing the size of reproductive plants, since plants that bolt from smaller rosettes tend to produce less seed (Falińska 1997). In the case of nodding thistle, the rosette-feeding weevil (Trichosirocalus horridus), was shown to contribute more to population decline than seed feeders since it reduced the growth and survival of individual plants in the population (Shea et al 2006).…”

“…Care was taken to collect plants of similar size (rosette diameter) and same habitat (roadside). Due to the facultative biennial nature of the plant (Falińska 1997), overwintered rosettes of sufficient size (i.e. >40 cm diameter) were collected to ensure that they would able to flower and produce seeds (Falińska 1997).…”

“…Due to the facultative biennial nature of the plant (Falińska 1997), overwintered rosettes of sufficient size (i.e. >40 cm diameter) were collected to ensure that they would able to flower and produce seeds (Falińska 1997). The plants were transplanted into 12-litre pots containing a standard potting mix (54% aged bark, 45% sand, 1% nutrients, by weight) with added nutrients as Osmocote® 17-11-10 (N-P-K), lime, superphosphate, sulphate of potash and calcium nitrate.…”

The variability of population and individual traits of medicinal plant Valeriana officinalis L. var. officinalis Mikan under different site conditions

“…Such a phenomenon is named "Oskar syndrome" (53), triggered by unfavourable site conditions, was observed in several tree species, in which seedlings delay the production of branches, flowers and seed until the canopy becomes open due to death of other trees. This delay of maturation was also noticed in herbaceous species inhabiting meadows in the course of succession, such as Cirsium palustre (54).…”