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Following the Turnover of Soil Bioavailable Phosphate in Mediterranean Savanna by Oxygen Stable Isotopes
Author(s) -
Weiner T.,
Gross A.,
Moreno G.,
Migliavacca M.,
Schrumpf M.,
Reichstein M.,
Hilman B.,
Carrara A.,
Angert A.
Publication year - 2018
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1029/2017jg004086
Subject(s) - soil water , incubation , cycling , nutrient , phosphorus , zoology , environmental chemistry , chemistry , phosphate , bioavailability , stable isotope ratio , ecology , biology , biochemistry , organic chemistry , history , bioinformatics , physics , archaeology , quantum mechanics
Soil phosphate oxygen isotope analysis (δ 18 O P ) emerges as an effective method to trace the cycling of phosphorus (P) in soils. This study uses δ 18 O P 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 × 10 6 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 δ 18 O values of soil bioavailable P during incubation of soils with a pulse of P and in addition measured the δ 18 O P in soil sampled at the site. In the incubations, the δ 18 O P 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 18 O‐enriched incubation media water. The change in δ 18 O P 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 δ 18 O P 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.