Zur Besiedlung von Ackerbrachen im Kyffhäusergebirge durch Stipa pennata L., Stipa pulcherrima K. Koch, Stipa tirsa Steven em. Čelak. und Stipa capillata L. aus populationsökologischer und pflanzensoziologischer Sicht

Abstract

Hofmann, K.; Pusch J.; Mann, S.; Tischew, S.: Colonization of fallow fields in the Kyffhäuser mountains by Stipa pennata L., Stipa pulcherrima K. Koch, Stipa tirsa Steven em. ČČelak. and Stipa capillata L. considering aspects of population ecology and plant sociology. – Hercynia N.F. 41 (2008): 83 –97.This paper focuses on the question why Stipa pennata, Stipa pulcherrima, Stipa tirsa und Stipa capillata could not colonize old fallow fields in the Kyffhäuser Mountains in a time period of several decades even though adjacent donor populations are available. We carried out germination experiments in open beds under controlled conditions and found that a high amount of the introduced seeds were able to germinate and develop to juvenile plants. Best results were obtained in Stipa tirsa where at least 70 percent of the seeds germinated. However, we also detected for Stipa pennata, Stipa pulcherrima und Stipa tirsa a primary dormancy that postponed the germination at least until the next spring. In the third year a high share of the Stipa pennata, Stipa pulcherrima and Stipa capillata individuals developed inflorescences whereas only few Stipa tirsa individuals showed inflorescences obviously due to intraspecific competition in the dense stands. Our field mappings showed a distinct dominance of Bromus erectus or Brachypodium pinnatum on the fallow fields at the Mittelberg and the Falkenburg in contrast to a low density of these species on the Stipa-rich old grazing sites. The phytosociological analyses and the calculation of quantitative Ellenberg indicator values revealed also distinct differences between the fallow fields and the Stipa-rich old grazing sites. The vegetation types on the fallow fields showed higher Ellenberg indicator values for nitrogen availability and lower Ellenberg indicator values for continental climate whereas the vegetation types on the Stipa-rich old grazing sites displayed lower Ellenberg indicator values for nitrogen availability and higher indicator values for continental climate. The vegetation type Festuco valesiacae - Stipetum capillatae and Stipetum stenophyllae could establish only on the more exposed and less nutrient-rich sites. Therefore we conclude that a large-scale and permanent colonization of the investigated fallow fields by Stipa pennata, Stipa pulcherrima und Stipa tirsa is only possible if elaborate restoration measures are carried out. Due to this fact we would like to point out that management and protection of the existing Stipa-rich vegetation types in the Kyffhäuser Mountains is very important.