Effects of a severe drought on a permanent meadow in the Jura mountains

In order to determine the impacts of a severe summer drought on the agronomic value and diverse physiological and functional characteristics of a permanent meadow, a trial was carried out in 2012 on a mountain farm located in the Swiss Jura (1200 m). Two factors – management type (mowing vs grazing) and moisture (drought vs control) – were tested with a 2 × 2-design. The drought stress was simulated by means of rain shelters for a duration of 84 days. The grazed plots were grazed every four weeks with ewes, whereas the mowed plots were cut three times in the season. The biomass and the quality of the forage were monitored across the season. The botanical composition of the meadow and the functional traits of the 16 most abundant species were assessed before and after the drought treatment. The photosynthesis rate, the pre-dawn leaf water potential and the respiration of the soil were all measured. Apart from important yield losses, the drought stress also led to changes in the nutrient contents and the nutritive value of the forage. The ecophysiological measurements reflected a slowdown of the whole ecosystem. The grazed plots, characterized by a shorter vegetation, were more impacted by the drought than the mown plots.