The impact of different cutting regimes on population density of Jacobaea aquatica (Hill) G. Gaertn., B. Mey. & Scherb. and grassland vegetation

Abstract

Jacobaea aquatica is a monocarpic Asteraceae growing in wet grasslands of low management intensity. It is considered a noxious weed because it contains pyrrolizidine alkaloids, which cause health problems to livestock. The aim of this study was to develop management options to reduce the population density of J. aquatica in meadows of high nature conservation value without negative impacts on plant species diversity. The study site is located at the Hercynian part of Lower Austria near the city of Gmünd. The effect of five different cutting regimes on population density and seed production of J. aquatica as well as on species richness of the surrounding vegetation was tested on permanent plots from 2007 to 2012. One cut in October diminished J. aquatica but species richness decreased. Two cuts during the peak flowering period (July and August) and October reduced the population density of J. aquatica by c. 70% without obvious loss of species richness. Traditionally practiced two cuts in June and September lead to a rapid population growth of J. aquatica. According to our results, a first cut in June providing non-toxic fodder and two additional cuts during peak flowering are appropriate to reduce J. aquatica and to maintain biodiversity.