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Rhizosphere-driven increase in nitrogen and phosphorus availability under elevated atmospheric CO2 in a mature Eucalyptus woodland
- Ochoa-Hueso, Raúl, Hughes, John, Delgado-Baquerizo, Manuel, Drake, John E., Tjoelker, Mark G., Piñeiro, Juan, Power, Sally A.
- Plant and soil 2017 v.416 no.1-2 pp. 283-295
- Eucalyptus, carbon dioxide, carbon dioxide enrichment, carbon sequestration, cellulose, enzyme activity, forest ecosystems, nitrogen, nutrient availability, phosphorus, plant growth, rhizosphere, soil, soil organic matter, starch, woodlands, Australia
- BACKGROUND AND AIMS: Rhizosphere processes are integral to carbon sequestration by terrestrial ecosystems in response to rising concentrations of atmospheric CO₂. Yet, the nature and magnitude of rhizosphere responses to elevated CO₂, particularly in nutrient and water-limited forest ecosystems, remain poorly understood. METHODS: We investigated rhizosphere responses (enzyme activities and nutrient availability) to atmospheric CO₂ enrichment (ambient +150 μmol CO₂ mol⁻¹) in a phosphorus-limited mature eucalypt woodland in south-eastern Australia (the EucFACE experiment). RESULTS: Following 17 months of treatment, the activity of rhizosphere soil exoenzymes related to starch and cellulose degradation decreased between 0 and 10 cm and increased from 10 to 30 cm depth under elevated CO₂. This response was concurrent with increases in nitrogen and phosphorus availability and smaller C:P nutrient ratios in rhizosphere soil under elevated CO₂. CONCLUSIONS: This nutrient-poor eucalypt woodland exhibited rhizosphere responses to atmospheric CO₂ enrichment that increased nutrient availability in rhizosphere soil and suggest accelerated rates of soil organic matter decomposition, both of which may, in turn, promote plant growth under elevated CO₂ concentrations.