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In the Alps, many summer pastures are under-used due to the decreasing number of livestock. Optimizing the grazing management of heterogeneous pastures implies a better understanding of foraging habits of cattle. The aim of this study was to precise the relationships between cattle behaviour and the characteristics of the vegetation. The experiment was carried out on a pasture encroached by shrubs (mainly Alnus viridis) and composed of four contrasted vegetation units at 1800 m a.s.l. Four beef cows were monitored in a paddock of 2.9 ha by Differential Global Positioning System (DGPS) during three rotations, in order to analyze the spatial and temporal occupation pattern. The open grasslands and, to a lesser extent, the tall herb community were significantly more visited than expected if cattle had foraged at random. The shrubby areas were far less visited than expected at random. The monitoring also revealed differences across rotations. Vegetation surveys were also performed to determine the specific contribution and the grazing frequency of the encountered plant species. The most eaten herbaceous plants were not necessarily those known to be the most palatable, even if graminoids were more selected than other plants. Leontodon hispidus, Agrostis capillaris, Festuca rubra, and Luzula sylvatica were the most selected species, whereas Veratrum album and Trollius europaeus were completely avoided. The consumed forage was of better quality than the forage collected at random and its nutrient content showed less variability and remained more constant over the three rotations. The results highlight that the selection processes exerted by cattle are important. They occur at different levels (species, vegetation type, in time) and confirm that an integrative approach is necessary for improving the understanding of cattle foraging behaviour in heterogeneous mountain pastures.

Drought can occur at different times during the grassland growing season, likely having contrasting effects on forage production when happening early or later in the season. However, knowledge about the interacting effects of the timing of drought and the development stage of the vegetation during the growing season is still scarce, thus limiting our ability to accurately predict forage quantity losses. To investigate plant community responses to drought seasonality (early- vs. late-season), we established a drought experiment in two permanent grasslands of the Swiss Jura Mountains that are used for forage production. We measured three plant functional traits, including two leaf traits related to plant economics (specific leaf area, SLA; leaf dry matter content, LDMC) and one hydraulic trait related to physiological function (predicted percentage loss of hydraulic conductance, PLCp), of the most abundant species, and plant above-ground biomass production. Plant species composition was also determined to calculate community-weighted mean (CWM) traits. First, we observed that CWM trait values strongly varied during the growing season. Second, we found that late-season drought had stronger effects on CWM trait values than early-season drought and that the plant hydraulic trait was the most variable functional trait. Using a structural equation model, we also showed that reduction in soil moisture had no direct impacts on above-ground biomass production. Instead, we observed that the drought-induced decrease in above-ground biomass production was mediated by a higher CWM PLCp (i.e. higher risk of hydraulic failure) and lower CWM SLA under drought. Change in CWM SLA in response to drought was the best predictor of community above-ground biomass production. Our findings reveal the importance of drought timing together with the plant trait responses to assess drought impacts on grassland biomass production and suggest that incorporating these factors into mechanistic models could considerably improve predictions of climate change impacts.

Here we report successful interferometric coupling of two large telescopes with single-mode fibers. Interference fringes were obtained in the 2- to 2.3-micrometer wavelength range on the star 107 Herculis by using the two Keck 10-meter telescopes, each feeding their common interferometric focus with 300 meters of single-mode fibers. This experiment demonstrates the potential of fibers for future kilometric arrays of telescopes and is the first step toward the 'OHANA (Optical Hawaiian Array for Nanoradian Astronomy) interferometer at the Mauna Kea observatory in Hawaii. It opens the way to sensitive optical imagers with resolutions below 1 milli-arc second. Our experimental setup can be directly extended to large telescopes separated by many hundreds of meters.