Water availability is a key driver of net primary production. Extreme drought events are forecasted to increase in intensity and frequency within the century with big impacts on ecosystem productivity. This will also have important economic consequences, notably in grasslands, which are the core areas for forage production worldwide. However, temperate grasslands commonly used for forage production seem to vary in their sensitivity to drought, likely due to the diversity of grassland botanical composition, management practices, soil properties and local climatic conditions. Plant functional traits have been shown to strongly vary along soil moisture gradients, and thus could be good indicators of the plant response to drought Plant hydraulic traits measured at the community scale have, up till now, rarely been used to assess grassland responses to drought.

In a recent study published in AoBP, Vitra et al. used the percentage loss of conductivity (PLCp) as a plant community hydraulic trait to observe its interactions with more commonly used plant leaf economic traits (such as specific leaf area and leaf dry matter content) and its direct effects on grassland productivity under drought. Using a structural equation model, the authors showed that reduction in soil moisture had no direct impacts on aboveground biomass production. Instead, they observed that the drought-induced decrease in aboveground biomass production was mediated by a higher predicted percentage loss of hydraulic conductance and lower specific leaf area under drought. These findings reveal the importance of using drought timing together with 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.

Researcher highlight

Amarante Vitra grew up in France and moved to Switzerland in 2014 to conduct her Masters thesis in tree ecophysiology (freezing resistance) at the University of Basel. She then joined the Laboratory of Ecological Systems (ECOS) at the Swiss Federal Institute of Technology in Lausanne (EPFL) and Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) to do her PhD thesis under the supervision of Prof. Alexandre Buttler and Dr Pierre Mariotte. Amarante is currently finishing her PhD project entitled ‘Responses of permanent grasslands to drought during the plant growing season: combining agronomic, functional and ecophysiological approaches’.

Amarante is a plant ecologist interested in using a more mechanistic approach, linking plant leaf economic and physiological traits, to better understand plant community resistance to drought. She is also interested in applying this knowledge to improving grassland management practices under ongoing and predicted climate changes.