Short-term carbon dynamics in a temperate grassland and heathland ecosystem exposed to 104 days of drought followed by irrigation

Temperate ecosystems are susceptible to drought events. The effect of a severe drought (104 days) followed by irrigation on the plant C uptake, its assimilation and input of C in soil were examined using a triple 13CO2 pulse-chase labelling experiment in model grassland and heathland ecosystems. First 13CO2 pulse at day 0 of the experiment revealed much higher 13C tracer uptake for shoots, roots and soil compared to the second pulse (day 44), where all plants showed significantly lower 13C tracer uptake. After the third 13CO2 pulse (day 70), very low 13C uptake in shoots led to a negligible allocation of 13C into roots and soil. During irrigation after the severe drought, the 13C tracer that was allocated in plant tissues during the second and third pulse labelling was re-allocated in roots and soil, as soon as the irrigation started. This re-allocation was higher and longer lasting in heathland compared to grassland ecosystems.