Long-term atmospheric carbon dioxide enrichment decreases soil phosphorus availability in a grazed temperate pasture

Abstract

Elevated atmospheric carbon dioxide (eCO₂) associated with climate change increases plant production and soil nutrient transformations. However, changes in soil phosphorus (P) availability and dynamics are unclear. We used the long-term New Zealand Free Air CO₂ Enrichment (FACE) experiment to quantify changes in P availability and soil P fractions as well as chemical and biological parameters in response to ambient and elevated CO₂ (up to 500 ppm) concentrations. Results revealed that labile and moderately labile soil inorganic P decreased in response to eCO₂, while organic P increased. Accumulation of organic P was related to enhanced biological activity, increased inputs of organic P from root detritus, and immobilization on reactive mineral surfaces. The findings of this study confirmed that elevated CO₂ had a major impact on the dynamics and bioavailability of soil P under grazed pasture, which may be further impacted by continued climate change.