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Climatic disturbances have a long-term effect on grasslands

The purpose of this study was to understand how grasslands respond to climatic variations in order to adapt practices that will favour the recovery of species and thus ensure long-term maintenance of the agricultural and environmental services rendered by grasslands.

Summer 2003 during the heat-wave, the grasslands are completely
Updated on 09/16/2014
Published on 09/10/2014

Climate change scenarios predict a global warming of air, accompanied by an increase in the variability of rainfall, with a marked reduction being seen during the summer.  Under a hotter and drier climate, the production of high-quality forage, and the carbon sink function of grasslands, could thus be impaired in a marked and long-term manner.  The diversity of plant communities could however help to limit the negative effects of this stress.  The aim of this study was therefore to understand the response of grasslands to climate change so that practices can be adapted in order to favour the recovery of species and thus ensure long-term maintenance of the agricultural and environmental services rendered by grasslands.

A long-term effect of climate stress on biomass

Simulation of a gradient of summer climatic disturbances (reduction in rainfall associated with an average moderate warming (years 1 and 2) or marked warming (year 1): climatic stress of -156 to -249 mm rainfall induced wilting of the plant cover followed by rapid re-greening in the autumn of the first year.  This response - classically observed in grasslands - was not accompanied by a recovery of biomass production, which fell by 28% the first year and 25% the second year.  Under frequent cutting (4-6 cuttings each year), the effect of the climatic disturbance was more marked than under less frequent cutting (2-3 cuttings each year).

No attenuating effect of the species mix present

The presence of different functional groups (grasses, non-nitrogen fixing dicotyledons, legumes) within the plant community did not limit the negative effects of the climatic disturbance on grassland productivity.  In the third year, although the plots received the same rainfall, no recovery in grassland productivity was observed.  An abnormally warm and dry spring in the third year, inducing climatic stress of -141 mm, may have explained this latency period.

Improving species mixes

It is now necessary to improve our knowledge of the strategies adopted by grassland species regarding their resistance to and recovery from severe water stresses, in order to develop mixes that are more efficient and more sustainable over time.  To achieve this, experiments under semi-controlled conditions need to be carried out to compare the abilities of different species to accumulate non-structural carbohydrates, their depth of rooting and the lifespan of survival organs (aboveground and root meristems).