Kaninchen-Beweidung im Armerio-Festucetum trachyphyllae: Blühphänologie, Phytomasse-Entzug und Fraßpräferenzen

Abstract

Faust, C.; Storm, C.; Schwabe, A.: Impact of rabbit grazing in Armerio-Festucetum trachyphyllaevegetation: flower phenology, extraction of phytomass and diet preferences. – Hercynia N.F. 40 (2007): 177-192.Optimized nature conservation and management strategies are necessary to preserve Armerio-Festucetum trachyphyllae vegetation, which is also an important habitat for a species-rich flower-visiting insect fauna, if it contains diverse flower resources. The remaining larger areas of this community in the northern upper Rhine valley are severely disturbed by a large rabbit population, which developed especially after the dry year 2003. In this study we analyse whether rabbits feed on flower resources that are important for flower-visiting wild bee species (Hymenoptera, Apoidea), and if they have an impact on flower phenology. The question which Plant Functional Types (PFTs) are mainly extracted by rabbits (Leguminosae, other herbs, graminoids) is also considered. We analysed the effects by means of a replicated six-fold split-plot design (without rabbits K-, with rabbits K+). Additionally we were able to determine the extraction rates (repeatedly mown phytomass of PFTs, afterwards dried) by comparison of sheltered mini-exclosures (1 m x 2 m) and side-by-side comparative plots. Flowers especially of entomophilous species could be recorded quantitatively. The results show that grazing had a significant negative effect in that it reduces flower quantities. Some species reacted by regrowth and a shift of flower-phenological phases (e.g. Armeria maritima ssp. elongata, Berteroa incana, Sedum acre). Rabbits preferred Fabaceae and “other herbs”, but they also fed on graminoids poor in sclerenchyma. Dietary preferences changed during the year: in summer they mainly fed on Fabaceae and other herbs, in spring and early summer they additionally fed on graminoids, which were partly rejected in summer and autumn. Many of the preferred plant species were entomophilous (e.g. Armeria, Erodium cicutarium, Medicago falcata). Feeding impact on species with poisonous ingredients (e.g. Euphorbia cyparissias) and those with a high degree of sclerenchyma (e.g. Carex hirta) or which are pubescent (e.g. Geranium molle) was very low. Compared to the K- plots there was partly an extraction of up to 100 % of flowers in the K+ plots.