Summary
This field study used ¹³CO₂ pulse labeling to investigate how extreme summer drought alters short-term carbon cycling in an intensively managed Swiss grassland. Drought reduced shoot carbon incorporation and increased below-ground carbon allocation, whilst simultaneously reducing soil CO₂ efflux rates; predisposition by spring drought increased grassland sensitivity to subsequent summer drought, suggesting potential cumulative impacts under future climate scenarios.
Regional applicability
The findings are directly applicable to United Kingdom grassland systems, particularly lowland managed grasslands vulnerable to summer drought stress. The study's demonstration of altered carbon coupling and reduced respiration under drought is relevant to UK climate projections and grassland productivity forecasts, though local soil type, management intensity, and drought duration may modulate responses.
Key measures
Soil CO₂ efflux and isotopic composition (using quantum cascade laser spectrometer); ¹³C tracer incorporation into shoots, roots, and soil over 31 days; carbon allocation ratios; soil respiration rates
Outcomes reported
The study measured the short-term coupling of freshly assimilated photosynthates to roots and soil CO₂ efflux under drought conditions using ¹³CO₂ pulse labeling, tracing label incorporation into shoots, roots, and soil over 31 days. Drought reduced carbon incorporation into shoots, increased below-ground allocation, and reduced soil CO₂ efflux rates, with only 60% of tracer lost via respiration under drought versus 75% under control conditions.
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