Summer rain and wet soil but not management correlate with the distribution of a toxic plant in production grasslands

Abstract In the northern forelands of the Alps, farmers report an increase of Jacobaea aquatica in production grasslands. Due to its toxicity, the species affects grassland productivity and makes costly control measures necessary. We are investigating the extent to which management practices or climatic factors are responsible for the increase of the species, and how the situation will change as a result of climate change. We tested for effects of management intensity, fertilization, agri-environmental measures and injuries to soil and sward and modeled the species' risk of occurrence under rcp4.5 and rcp8.5 scenarios. Main determinants of the occurrence of the species are soil type and summer rainfall. A high risk is associated with wet soils and more than 400 mm rain between June and August. An influence of the management related factors could not be detected. Under the climate scenarios, the overall occurrence risk decreases, and shifts to the wetter alpine regions. The reported increase is rather a shift in the occurrence of the species due to the altered precipitation situation. Under future climatic conditions, the species will decline and retreat to higher regions in the Alps. This will decrease the risk of forage contamination in lower production grassland.