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.

温带生态系统易受干旱事件影响。本研究以模拟草原与石楠荒原生态系统为实验对象，采用三重¹³C-二氧化碳脉冲追踪标记实验(triple ¹³CO₂ pulse-chase labelling experiment)，探究了为期104天的极端干旱后辅以灌溉，对植物碳吸收、碳同化以及土壤碳输入的影响。实验第0天开展的首次¹³C-二氧化碳脉冲标记显示，地上部分、根系与土壤的¹³C示踪剂吸收量均显著高于第44天的第二次脉冲标记，此时所有植物的¹³C示踪剂吸收量均大幅降低。实验第70天进行第三次¹³C-二氧化碳脉冲标记后，地上部分的¹³C吸收量极低，导致向根系与土壤的¹³C分配量可忽略不计。在极端干旱后的灌溉阶段，第二次与第三次脉冲标记中已分配至植物组织的¹³C示踪剂，会在灌溉启动后迅速向根系与土壤发生再分配。与草原生态系统相比，石楠荒原生态系统中的这种碳再分配程度更高、持续时间更久。