Effects of extreme drought on grasslands Evaluation of the buffering effect of plant diversity using an experimental approach
Hernandez, P | Picon-Cochard, C
The frequency and magnitude of extreme drought events are expected to increase with climate change. Consequently, it is important to assess the ability of temperate grassland to resist and recover from more frequent and intense drought stress. To study this topic, we established a mesocosm experiment in autumn 2012: large pots (100 L) containing combinations of grassland species (1, 2 or 5 species) were placed on weighing scales to continuously measure the actual evapotranspiration of the plant canopy. Species selected (four grasses and one legume) were representative of temperate upland grasslands on fer- tile soils. An extreme summer drought was applied to half the pots and plant recovery following rewetting was monitored. Total biomass and evapotranspiration were analyzed to test the effects of species diversity on the resistance and recovery of grasslands to extreme drought. As expected, drought dramatically reduced by 79% biomass of all mixtures. The 5 species mixtures showed higher drought avoidance by maintaining inte- grated water-use efficiency and took up water at deeper soil layers than the less diverse mixtures during drought. These findings indicated that buffering effect of diversity during drought occurs for the 5-species mix- tures, possibly due to below-ground niche differentiation. This study emphasizes the high capacity of grass species mixtures to recover after an extreme drought. Keywords.
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