Animals & nature · 2023
Why can grasslands produce more after a drought?
In a field experiment, soil that had experienced drought and rewetting boosted grass productivity, counteracting negative effects left in the plants themselves. The soil effect improved plant nitrogen nutrition and photosynthetic capacity.
Details
Grasslands recovering from drought have repeatedly been shown to produce more biomass than grasslands that were not drought-stressed. The mechanisms behind this unexpectedly high production, however, were not understood.
To separate plant-intrinsic drought legacy effects from plant-extrinsic soil effects during recovery, researchers designed a factorial field experiment. Lolium perenne plants exposed either to a 2-month drought or to well-watered control conditions were transplanted into control soil and drought-stressed soil, then rewetted.
When separated from soil-mediated effects of drought and rewetting (DRW), formerly drought-stressed plants (DRWp) showed negative legacy effects compared with control plants (Ctrp): 13% lower aboveground productivity, restricted nitrogen nutrition, and higher δ13C. In contrast, plants grown on formerly drought-stressed soil (DRWs) had 82% higher aboveground productivity, improved nitrogen nutrition, and higher δ13C than plants grown on control soil (Ctrs), regardless of the plants' pretreatment.
The study concludes that soil-mediated DRW legacy effects cause the higher post-drought productivity of recovering perennial grasslands relative to non-drought-stressed controls. These soil effects improve plant nitrogen nutrition and photosynthetic capacity and counteract negative plant-intrinsic drought legacy effects.
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