Responses of beech and spruce foliage to elevated carbon dioxide, increased nitrogen deposition and soil type

Although enhanced carbon fixation by forest trees may contribute significantly to mitigating an increase in atmospheric CO₂, capacities for this fixation vary greatly among different tree species and locations. In a study published in AoB PLANTS, Günthardt-Goerg and Vollenweider compared reactions in the foliage of a deciduous and a coniferous tree species (important central European trees, beech and spruce) to an elevated supply of CO₂ and evaluated the importance of the soil type and increased nitrogen deposition on foliar nutrient concentrations and cellular stress reactions. Over four years young central European beech and spruce trees, growing on either acidic or calcareous forest soil, were exposed to elevated CO₂ and nitrogen deposition as forecast for the period 2050–2100. The elevated CO₂ had a positive fertilising effect on spruce foliage only, but led to an accumulation of tannins, cell wall thickening and an acceleration of cell senescence in both species. These effects were partly mediated by the soil type and nitrogen supply. Rising CO₂ concentration and nitrogen deposition may have similar effects on the leaf cell physiology – mechanistically – but induce contrasting, specific growth responses.