EGU2020-15473, updated on 21 Apr 2023
EGU General Assembly 2020
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Controls over phosphorus mineralization and immobilization rates in different tropical soils

Lucia Fuchslueger1,2, David Zezula1, Johann Püspök1, Leandro Van Langenhove2, Olga Margalef3, Alberto Canarini1, Christian Ranits1, Carlos Alberto Quesada4, Norma Salinas5, Eric Cosio5, Josep Penuelas3, Wolfgang Wanek1, Andreas Richter1, and Ivan Janssens2
Lucia Fuchslueger et al.
  • 1Centre for Microbiology and Environmental Systems Sciences, University of Vienna, Vienna, Austria
  • 2Department of Biology, Pants and Ecosystems, University of Antwerp, Antwerp, Belgium
  • 3Autonomous University of Barcelona, Ecological and Forestry Research Applications Center (CREAF)
  • 4National Institute of Amazonian Research (INPA), Manaus, Brazil
  • 5Seccion Química, Pontificia Universidad Católica del Peru, Lima, Peru

Highly weathered soils depleted in minerals and phosphorus (P) support large tracts of the tropical rainforests in the Central Amazon, which significantly contribute to the global carbon (C) sink. In these soils (oxisols and ferrasols), P is either occluded in Al/Fe-oxides, bound to the soil mineral matrix or in soil organic matter, and therefore not directly available for uptake as inorganic phosphate (Pi). To liberate Pi for plant or microbial uptake two processes are key: (i) changes of sorption-desorption equilibria of Pi with the soil matrix and (ii) the release of Pi from organic compounds (Po) catalyzed by enzymes, such as phosphatases. Plant roots and soil microbes have developed strategies to stimulate the release of P by accelerating P dissolution and desorption and by releasing extracellular phosphatases into the soil environment, which requires however C and energy investment. Because of P limitation in this ecosystem, the relative contributions of abiotic and biotic controls over P mineralization is of pivotal importance. Yet conclusive results are still scarce.

We therefore aimed to disentangle abiotic and biotic controls over P mineralization in tropical soils. To achieve this, we collected forest soils from the Amazon Basin covering a range of soil texture and P concentrations, determined soil mineralogy and measured gross P desorption and mineralization rates using a 33P isotope pool dilution assay. Moreover, we determined acid phosphatase activity rates and microbial biomass C and P. We found significant differences between the studied sites in gross P influx and efflux rates into the Pi pool. Gross influx rates (i.e. the sum of Pi desorption and organic P mineralization) exceeded efflux (i.e. sorption or biotic Pi uptake rates) only in sandy and silty soils, while in clayey soils efflux rates dominated P fluxes indicating a very high Pi sorption capacity. However, gross influx and efflux rates were not related to total or dissolved P. Microbial biomass and acid phosphatase activity normalized to microbial biomass C were highest in sites with overall low total P microbial biomass P accounting for up to 40 % of total P in low P soils. We therefore conclude that in low P soils organic P turnover plays a major role in soil P cycling, and despite of the high P sorption capacity of clay rich soils, microbes can be strong competitors for plant available P.

How to cite: Fuchslueger, L., Zezula, D., Püspök, J., Van Langenhove, L., Margalef, O., Canarini, A., Ranits, C., Quesada, C. A., Salinas, N., Cosio, E., Penuelas, J., Wanek, W., Richter, A., and Janssens, I.: Controls over phosphorus mineralization and immobilization rates in different tropical soils, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15473,, 2020.


Display file