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The dynamics of the population of a steppe perennial Senecio macrophyllus M.BIEB. during xerothermic grassland overgrowing

100%

Czarnecka B.

Acta Societatis Botanicorum Poloniae

2009

tom 78

nr 3

247-256

The study aimed to determine the long-term changes of the Senecio macrophyllus M.BIEB. population traits: the abundance, reproduction mode, individual fecundity, seed rain and recruitment of new genets in the course of xerothermic grassland overgrowing. The study had also the applied goal: to estimate the chances of "special care" species to survive in the changing environment without management regime for the maintenance of grassland. The model object was the island population of large-leaved ragwort on Biała Góra (the White Mountain) near Tomaszów Lubelski, South-East Poland. To achieve these aims I used the following sets of data: phytosociological relev,s made in plant communities in an interval of 16-18 years; repeated elaboration of the numbers and life-stage structure of the population, both by non-surface and surface method; observation of plants, life cycle in 50 labelled genets; population reproduction and seed rain amounts. The area of an open xerothermic grassland decreased due to the process of overgrowing by bushes which was accompanied by the increasing coverage of forest and meadow herbs as well as monocotyledons, mainly Brachypodium pinnatum and Calamagrostis epigejos. The abundance of the S. macrophyllus population noticable diminished. The flowering mode has been changing during years from an oscillation to a chaotic type which caused the significant decreasing of the individual fecundity, population reproduction and seed rain. In last years it was reflected in the interruption of juveniles’ recruitment.

Formation and dynamics of the metapopulation of Senecio rivularis (Waldst. and Kit.) DC. (Asteraceae) at the limit of its geographical range: where, when, by what means?

72%

Czarnecka B.

Polish Journal of Ecology

2011

tom 59

nr 2

In the studies on the metapopulation system two aspects are important: cognitive and practical. The former indicates that a metapopulation is a demographic structure of a higher level than coenotic or local populations and aims at recognition of relations between particular populations of a given species. The practical aspect reflects the issues of the dynamics and/or the extinction rate in particular populations and indicates potential habitats which can be colonized. The study of the Senecio rivularis metapopulation is created by relatively abundant population of ragwort in the Roztocze Highlands, Roztocze National Park, south-eastern Poland, recognized as the source population and three other called marginal or sink populations as well as potentially suitable habitats which are distributed as islands in adjacent hydrogenic areas. The distances between particular populations range from 1.3 to 6.5 km. As a long-lived, iteroparous rhizomatous clonal plant, insect-pollinated and anemochoric one, so having adaptations both for ‘escape in time’ and ‘escape in space’, S. rivularis may be treated as the model object of the study on the metapopulation level. The following hypotheses were put forward: (1) the spatial pattern, size and life-stage structures of particular populations reflect the time of their origin in the meta-system; (2) hydrochory is a complementary or alternative way of migration of anemochoric diaspores; (3) local watercourses and hydro-technical activity affect the formation and dynamics of S. rivularis metapopulation. The multi-aspect studies of the source population were conducted in the years 1987–2007. They aimed to establish the density, spatial pattern and life-stage structure of the S. rivularis population, both at a large scale, i.e. in the whole population (three times) and at a small scale, i.e. on the level of three particular clumps (four times). The size structure of generative genets and ramets in the whole population was elaborated five times. In the greatest of the other populations in the meta-system, the size structure was elaborated twice (2002, 2007) while the study of spatial and life-stage structures was done only once, in the first period, because of the disturbance of a greater part of the population in the next years. In the two remaining localities all plants were counted thanks to small abundance of the populations. Considerable changes in the spatial organization and life-stage structure of genets in the source and sink populations exhibited that colonization in the meta-system of S. rivularis proceeds in accordance with an island model of the ‘stepping stone’ type, downstream the river. Renaturalization of water relations of river catchment areas and construction of the so-called small retention objects affect the formation and dynamics of S. rivularis metapopulation which reflects at least some dynamics phases observed at the level of the source population: progressive, stable, fluctuation and/or regressive, and extinction phases. Knowledge of the density, life-stage and size structures of plants in a population facilitates a highly reliable determination of the development phase of a given local population in the meta-system and prognosis of its future.

Ograniczanie wyników

1 Acta Societatis Botanicorum Poloniae

1 Polish Journal of Ecology

2 Czarnecka B.

1 2011

1 2009

Wyniki wyszukiwania

The dynamics of the population of a steppe perennial Senecio macrophyllus M.BIEB. during xerothermic grassland overgrowing

Formation and dynamics of the metapopulation of Senecio rivularis (Waldst. and Kit.) DC. (Asteraceae) at the limit of its geographical range: where, when, by what means?