Rhizosphere-driven increase in nitrogen and phosphorus availability under elevated atmospheric CO2 in a mature Eucalyptus woodland
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.
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).
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.
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.
KeywordsClimate change Elevated CO2 Free-air CO2 enrichment Fine roots Forests Nutrient limitation Phosphorus Rhizosphere
We are grateful to Prof. David Ellsworth, Burhan Amiji, Dr. Craig Barton, Dr. Vinod Kumar and Steven Wohl for managing the EucFACE facility. EucFACE is an initiative supported by the Australian Government through the Education Investment Fund, the Department of Industry and Science, and the Australian Research Council in partnership with the Western Sydney University. Facilities at EucFACE were built as an initiative of the Australian Government as part of the Nation-building Economic Stimulus Package. The authors declare no conflicts of interest.
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