EGU2020-4084
https://doi.org/10.5194/egusphere-egu2020-4084
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

From rock-eating to vegetarian ecosystems — plant phosphorus acquisition strategies along a Chilean precipitation gradient

Sandra Spielvogel1,2, Moritz Köster2,3, Svenja Stock3, Francisco Nájera4, Khaled Abdallah5, Anna Gorbushina5,6, Jörg Prietzel7, Francisco Matus8, Wantana Klysubun9, Jens Boy10, Yakov Kuzyakov11, and Michaela Dippold3
Sandra Spielvogel et al.
  • 1Christian-Albrechts-University Kiel, Institute of Plant Nutrition and Soil Science, Soil Science, Kiel, Germany (s.spielvogel@soils.uni-kiel.de)
  • 2Instiute of Geography, University of Bern, Bern, Switzerland
  • 3Biogeochemistry of Agroecosystems, University of Goettingen, Goettingen, Germany
  • 4Department of Chemical Sciences and Natural Resources, Universidad de La Frontera, Chile
  • 5Federal Institute for Material Research and Testing, Berlin, Germany
  • 6Freie Universität Berlin, Department of Earth Sciences & Department of Biology Chemistry Pharmacy, Malterserstr. 74-100, D-12249 Berlin, Germany
  • 7Research Department Ecology and Ecosystem Management, Chair of Soil Science, Technical University of Munich, Freising, Germany
  • 8Laboratory of Conservation and Dynamic of Volcanic Soils, Universidad de La Frontera, Chile
  • 9Synchrotron Light Research Institute, Nakhon Ratchasima, Thailand
  • 10Institute of Soil Science, Leibniz Universität Hannover, Hannover, Germany
  • 11Soil Science of Temperate Ecosystems, Agricultural Soil Science, University of Goettingen, Goettingen, Germany

Besides nitrogen, phosphorus (P) is the major limiting nutrient of terrestrial primary productivity, with major P stocks being bound in soils. Stocks, speciation, and bioavailability of soil P differ among ecosystem types and with rock weathering status, which are both driven by climatic conditions. Microorganisms and plants have developed a range of strategies to mobilize P from organic and inorganic sources, e.g. expression of extracellular phosphatases and excretion of low-molecular-weight organic acids (LMWOA). However, the impact of precipitation, vegetation type, and soil P speciation on plant P acquisition strategies is not well understood, yet.

A semi-desert-to-humid-temperate-rainforest ecosystem sequence was investigated. Soil samples were taken from three sampling sites, all developed on granodiorite, comprising a precipitation gradient (66 mm a-1 to 1469 mm a-1) along the Chilean Coastal Cordillera. Small-scale gradients (mm) from single roots to bulk soil in three depths were sampled to examine changes in P speciation, enabling the identification of local P depletion by plant roots and differences in P-speciation between rhizosphere and non-rhizosphere soil. Phosphorus speciation was examined by X-ray absorption near edge structure analysis. LMWOA as biotic weathering agents, and acid phosphatase kinetics as proxy for organic P recycling, were quantified. The aim was to disentangle the impact and functions of roots and associated microorganisms on driving agents of P-cycling.

Rhizosphere P speciation in soil changed considerably along the precipitation gradient from mainly primary P minerals in the semi-desert ecosystem to a dominance of organic P species in the humid-temperate rainforest. Contents of organically bound P were higher in root proximity compared to bulk soil in the humid-temperate rainforest soils (320 mg kg-1 and 70 mg kg-1, respectively) and in the topsoil of the Mediterranean woodland ecosystem (134 mg kg-1  and 62 mg kg-1, respectively).  In contrast, the rhizosphere soil was depleted in sesquioxide-adsorbed P in comparison to root-free bulk soil.

The content of LMWOA was correlated with inorganic P in soils of the semi-desert ecosystem, indicating intensive LMWOA exudation for biogenic P weathering of primary and secondary minerals. Under temperate rainforest LMWOA content, phosphatase activity, and microbial biomass carbon exhibited a negative correlation with secondary inorganic P forms but were positively linked to organic P species. We therefore conclude that P nutrition in this ecosystem relies less on weathering of P bearing minerals by LMWOA but is mainly based on organic P sources.

In terms of process understanding, these findings clearly show that LMWOA fundamentally change their role in the rhizosphere depending on the nutrient acquisition strategy of the respective ecosystem, which is affected by mean annual precipitation. While LMWOA facilitate biogenic weathering of P bearing minerals in the semi-desert, they mainly contribute to P recycling in the humid-temperate rainforest by preventing its precipitation and sorption. We conclude that P acquisition and cycling depends on the nutritional constrains of the given ecosystem: from biological weathering of inorganic P forms in the semi-desert driven by LMWOA and plant uptake to intensive P recycling from organic forms in the humid-temperate rainforest.

How to cite: Spielvogel, S., Köster, M., Stock, S., Nájera, F., Abdallah, K., Gorbushina, A., Prietzel, J., Matus, F., Klysubun, W., Boy, J., Kuzyakov, Y., and Dippold, M.: From rock-eating to vegetarian ecosystems — plant phosphorus acquisition strategies along a Chilean precipitation gradient, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4084, https://doi.org/10.5194/egusphere-egu2020-4084, 2020

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