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TREE EXPOSURE TO ELEVATED CO₂ INCREASES AVAILABILITY OF SOIL PHOSPHORUS

FAISAL N. KHAN¹, MARTIN LUKAC^2,*, FRANCO MIGLIETTA³, M. KHALID⁴ AND DOUGLAS L. GODBOLD¹

Abstract: Future high levels of atmospheric carbon dioxide will increase biomass production of terrestrial plants, however depletion of soil mineral nutrients may act as a negative feedback to increased growth. To test this, an ecosystem phosphorus budget was calculated in poplar grown under field conditions at ambient and elevated atmospheric CO₂ for 5 years.  The pools of total, plant available, weatherable and organic P were estimated, as well as the P storage in tree biomass components. While as a non-significant increase in amount of P taken up by the trees we observed, plant available P pools in the soil increased significantly. An increase in all soil P extractions was seen, with the greatest increase in an acid soluble P fraction which is considered to be the weatherable fraction. The formation of this P fraction may be biogenically driven and this additional P probably originates from weathering of occluded mineral pools.

¹Environment Centre for Wales, Bangor University, Bangor, UK.

²NERC Centre for Population Biology, Division of Biology, Imperial College London, Silwood Park Campus, Ascot, SL5 7PY, UK

³IATA-CNR, P.le delle Cascine, 18 50145 Firenze, Italy.

⁴Intitute of Soil & Environmental Sciences, University of Agriculture, Faisalabad, Pakistan