Zur Keimungsbiologie acht ausgewählter Xerothermrasenarten

Teil 3: Asteraceae

Abstract

Partzsch, M.: Germination biology of xerothermic grassland species - Part 3: Asteraceae. - Hercynia
N. F. 44 (2011): 211 – 227.
Currently, restoration of species-rich dry grassland communities is in focus of vegetation ecology. The
experimental approaches are seed addition and hay transfer. A requirement for the prediction of success
is a good knowledge of the germination biology of the introduced species. In this study eight xerothermic
species of the family Asteraceae were investigated: Achillea nobilis, A. pannonica, Centaurea
jacea subsp. angustifolia, C. scabiosa subsp. scabiosa, Hieracium pilosella, H. umbellatum, Tanacetum
corymbosum 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 from
November till March, to ensure hibernation until the next experimental phase in following spring. Seed
viability was tested before and after the experiments.
Results show that seeds of all species are not fully dormant. Seeds of Achillea nobilis und Taraxacum
laevigatum germinated completely in the year of harvest and also after hibernation. But only a half or
two-thirds of seeds of the other species germinated. This indicates an asynchronous germination and
means 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 germinated
in 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 showed
an 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 natural
cold stratification. The other species showed a change in temperature sensitivity. Because of the early
start of germination under warm and hot conditions, germination velocity is very high. After hibernation
the germination started few days earlier.
Results regarding the germination behaviour and seed viability allow to assign the species to two types
of 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 and
Tanacetum corymbosum.
Results suggest that the investigated species are well suitable for restoration of species-rich dry grassland
communities.