Following the Turnover of Soil Bioavailable Phosphate in Mediterranean Savanna by Oxygen Stable Isotopes

T. Weiner*, A. Gross, G. Moreno, M. Migliavacca, M. Schrumpf, M. Reichstein, B. Hilman, A. Carrara, A. Angert

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


Soil phosphate oxygen isotope analysis (δ18OP) emerges as an effective method to trace the cycling of phosphorus (P) in soils. This study uses δ18OP measurements to learn how the nutrient status (P and N) affects the biological turnover rates of P in the soil of a Mediterranean holm oak Savanna. Such ecosystems cover >3 × 106 ha at the Iberian Peninsula. The analysis was part of a large-scale nutrient manipulation experiment, where N and P were added. We followed the changes in δ18O values of soil bioavailable P during incubation of soils with a pulse of P and in addition measured the δ18OP in soil sampled at the site. In the incubations, the δ18OP values changed from the original value of the added P and approached a steady state of 16.3‰, which is 3.8‰ higher than the isotopic equilibrium with water. The steady state was higher with 18O-enriched incubation media water. The change in δ18OP values was more pronounced under trees, indicating a faster microbial P turnover rate. Incubation of soils fertilized with either P or N showed faster P turnover rate than control, implying N and P colimitation. Soil samples from P-fertilized plots displayed higher δ18OP than the fertilizer, rather than the expected decrease toward steady-state values, found at the control and N plots. The microbial P turnover rates during incubations were slower than the rates reported for lowland tropical forest with lower bioavailable P concentrations but resemble ecosystems with similar concentrations.

Original languageAmerican English
Pages (from-to)1850-1862
Number of pages13
JournalJournal of Geophysical Research: Biogeosciences
Issue number6
StatePublished - Jun 2018

Bibliographical note

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©2018. American Geophysical Union. All Rights Reserved.


  • Mediterranean savanna
  • bioavailable phosphate
  • oxygen stable isotopes
  • phosphate microbial turnover
  • phosphorus
  • soil P


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