Biogeochemical cycling of phosphorus in subsoils of temperate forest ecosystems
Bauke, Sara L.

von Sperber, Christian
Hoeschen, Carmen
Kandeler, Ellen
Kruse, Jens
Lewandowski, Hans
Marhan, Sven
Mueller, Carsten W.

Simon, Margaux
Tamburini, Federica
Uhlig, David
von Blanckenburg, Friedhelm

Lang, Friederike
Amelung, Wulf
DOI: https://doi.org/10.1007/s10533-020-00700-8
Persistent URL: http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/10723
Bauke, Sara L.; Institute of Crop Science and Resource Conservation (INRES) – Soil Science and Soil Ecology, University of Bonn, Bonn, Germany
von Sperber, Christian; Department of Geography, McGill University, Montreal, Canada
Hoeschen, Carmen; Chair of Soil Science, Department of Ecology and Ecosystem Management, Technical University of Munich, Freising-Weihenstephan, Germany
Kandeler, Ellen; Institute of Soil Science and Land Evaluation, Soil Biology Department, University of Hohenheim, Stuttgart, Germany
Kruse, Jens; Institute of Bio- and Geosciences – Agrosphere (IBG-3), Forschungszentrum Jülich GmbH, Jülich, Germany
Lewandowski, Hans; Institute of Bio- and Geosciences – Agrosphere (IBG-3), Forschungszentrum Jülich GmbH, Jülich, Germany
Marhan, Sven; Institute of Soil Science and Land Evaluation, Soil Biology Department, University of Hohenheim, Stuttgart, Germany
Mueller, Carsten W.; Department of Geosciences and Natural Resource Management, Section for Geography, University of Copenhagen, Copenhagen, Denmark
Simon, Margaux; Institute of Crop Science and Resource Conservation (INRES) – Soil Science and Soil Ecology, University of Bonn, Bonn, Germany
Tamburini, Federica; Institute of Agricultural Sciences, ETH Zurich, Lindau, Switzerland
Uhlig, David; Institute of Bio- and Geosciences – Agrosphere (IBG-3), Forschungszentrum Jülich GmbH, Jülich, Germany
von Blanckenburg, Friedhelm; GFZ German Research Centre for Geosciences, Earth Surface Geochemistry, Potsdam, Germany
Lang, Friederike; Chair of Soil Ecology, University of Freiburg, Freiburg (i. Br.), Germany
Amelung, Wulf; Institute of Bio- and Geosciences – Agrosphere (IBG-3), Forschungszentrum Jülich GmbH, Jülich, Germany
Abstract
Tree roots penetrate the soil to several meters depth, but the role of subsoils for the supply of nutrient elements such as phosphorus (P) to the trees is poorly understood. Here, we tested the hypothesis that increased P deficiency in the topsoil results in an increased microbial recycling of P from the forest subsoil. We sampled soils from four German temperate forest sites representing a gradient in total P stocks. We analyzed the oxygen isotopic composition of HCl-extractable phosphate (δ18OP) and identified differences in P speciation with increasing soil depth using X-ray absorption near-edge structure (XANES) spectroscopy. We further determined microbial oxygen demand with and without nutrient supply at different soil depths to analyse nutrient limitation of microbial growth and used nanoscale secondary ion mass spectrometry (NanoSIMS) to visualize spatial P gradients in the rhizosphere. We found that δ18OP values in the topsoil of all sites were close to the isotopic signal imparted by biological cycling when oxygen isotopes in phosphate are exchanged by enzymatic activity. However, with increasing soil depth and increasing HCl-P concentrations, δ18Ο values continuously decreased towards values expected for primary minerals in parent material at depths below 60 cm at sites with high subsoil P stocks and below more than 2 m at sites with low subsoil P stocks, respectively. For these depths, XANES spectra also indicated the presence of apatite. NanoSIMS images showed an enrichment of P in the rhizosphere in the topsoil of a site with high P stocks, while this P enrichment was absent at a site with low P stocks and in both subsoils. Addition of C, N and P alone or in combination revealed that microbial activity in subsoils of sites with low P stocks was mostly P limited, whereas sites with high P stocks indicated N limitation or N and P co-limitation. We conclude that subsoil P resources are recycled by trees and soil microorganisms. With continued weathering of the bedrock and mobilisation of P from the weathered rocks, P cycling will proceed to greater depths, especially at sites characterised by P limitation.