Zur Keimungsbiologie acht ausgewählter Xerothermrasenarten: Teil 3: Asteraceae

Abstract

Partzsch, M.: Germination biology of xerothermic grassland species - Part 3: Asteraceae. - HercyniaN. F. 44 (2011): 211 – 227.Currently, restoration of species-rich dry grassland communities is in focus of vegetation ecology. Theexperimental approaches are seed addition and hay transfer. A requirement for the prediction of successis a good knowledge of the germination biology of the introduced species. In this study eight xerothermicspecies of the family Asteraceae were investigated: Achillea nobilis, A. pannonica, Centaureajacea subsp. angustifolia, C. scabiosa subsp. scabiosa, Hieracium pilosella, H. umbellatum, Tanacetumcorymbosum and Taraxacum laevigatum.The germination experiments were carried out under three temperature-light regimes (8 / 4 °C, 20 /10 °C, 32 / 20 °C; 12 h light : 12 h darkness; 45 days). The collected seeds were divided in two parts.The first experiment was carried out in the year of harvest. The other diaspores were buried in soil fromNovember till March, to ensure hibernation until the next experimental phase in following spring. Seedviability was tested before and after the experiments.Results show that seeds of all species are not fully dormant. Seeds of Achillea nobilis und Taraxacumlaevigatum germinated completely in the year of harvest and also after hibernation. But only a half ortwo-thirds of seeds of the other species germinated. This indicates an asynchronous germination andmeans that, even under favourable conditions, only a proportion of seeds germinate in a certain time.Achillea nobilis showed an optimal germination at 20 / 10 °C, and Hieracium umbellatum at 32 / 20 °C,while Achillea pannonica, Centaurea scabiosa, Hieracium pilosella and Tanacetum corymbosum germinatedin a broad range of temperatures between 20 / 10 °C and 32 / 20 °C. Taraxacum laevigatum,however, germinated between 8 / 4 °C and 20 / 10 °C. Centaurea jacea and Hieracium pilosella showedan optimal germination at 20 / 10 °C and 32 / 20 °C, but also relatively high germination rates at 8 / 4 °C.Germination of Centaurea jacea and Taraxacum laevigatum was not significantly affected by naturalcold stratification. The other species showed a change in temperature sensitivity. Because of the earlystart of germination under warm and hot conditions, germination velocity is very high. After hibernationthe germination started few days earlier.Results regarding the germination behaviour and seed viability allow to assign the species to two typesof the diaspore bank: (1) transient: Achillea nobilis and Taraxacum laevigatum and (2) short-term persistent:Achillea pannonica, Centaurea jacea, C. scabiosa, Hieracium pilosella, H. umbellatum andTanacetum corymbosum.Results suggest that the investigated species are well suitable for restoration of species-rich dry grasslandcommunities.