Plant species rather than elevated atmospheric CO2 impacts rhizosphere properties and phosphorus fractions in a phosphorus deficient soil

By 2050, elevated atmospheric CO2 (eCO2) could stimulate plant growth, but dwindling phosphorus (P) stocks in the soil could limit growth. However, little is known about how eCO2 could affect soil P availability and dynamics in P-poor soils. Here, we conducted a 6-week pot experiment where three plant species were grown in a low-P soil under ambient (390 ppm) and eCO2 (700 ppm) to investigate plant growth, rhizosphere properties, and changes in soil P fractions. Our results showed that under P deficiency, plant biomass, P uptake, and rhizosphere properties did not respond to eCO2. Changes were noted by plant species. Compared to the control soil (unplanted pots), rhizosphere pH decreased the most under wheat, while microbial biomass P was higher under blue lupin. Among plant species, the blue lupin rhizosphere exhibited higher acid and alkaline phosphatase activity as well as organic anion release. Soil P fractions were impacted by plant species but similar across CO2 treatments.