From rock eating to vegetarian ecosystems — Disentangling processes of phosphorus acquisition across biomes

  • Low-molecular-weight organic acids (LMWOAs) are crucial for the mobilization and acquisition of mineral phosphorus by plants. However, the role of LMWOAs in mobilizing organic phosphorus, which is the predominant phosphorus form in at least half of the world’s ecosystems, especially in humid climates, is unclear. The mechanisms of phosphorus mobilization by LMWOAs depend on climate, mainly precipitation, and shape the phosphorus nutrition strategies of plants. We disentangled the impact of roots and associated microorganisms on mechanisms of phosphorus cycling mediated by LMWOAs by studying soils along an ecosystem-sequence (ecosequence) from arid shrubland (~70 mm yr-1), and Mediterranean woodland (~370 mm yr-1) to humid-temperate forest (~1470 mm yr-1). Phosphorus speciation in soil was examined by X-ray absorption near edge structure analysis (XANES). LMWOAs were quantified as biological rock-weathering and organic phosphorus mobilization agents and compared to kinetics of acidLow-molecular-weight organic acids (LMWOAs) are crucial for the mobilization and acquisition of mineral phosphorus by plants. However, the role of LMWOAs in mobilizing organic phosphorus, which is the predominant phosphorus form in at least half of the world’s ecosystems, especially in humid climates, is unclear. The mechanisms of phosphorus mobilization by LMWOAs depend on climate, mainly precipitation, and shape the phosphorus nutrition strategies of plants. We disentangled the impact of roots and associated microorganisms on mechanisms of phosphorus cycling mediated by LMWOAs by studying soils along an ecosystem-sequence (ecosequence) from arid shrubland (~70 mm yr-1), and Mediterranean woodland (~370 mm yr-1) to humid-temperate forest (~1470 mm yr-1). Phosphorus speciation in soil was examined by X-ray absorption near edge structure analysis (XANES). LMWOAs were quantified as biological rock-weathering and organic phosphorus mobilization agents and compared to kinetics of acid phosphatase as a proxy for organic phosphorus mineralization. Calcium-bound phosphorus in topsoils decreased from 126 mg kg-1 in the arid shrubland, to 19 mg kg-1 in the Mediterranean woodland and was undetectable in the humid-temperate forest. In contrast, organic phosphorus in topsoils in close root proximity (0–2 mm distance to roots) was absent in the arid shrubland but raised to 220 mg kg-1 in the Mediterranean woodland and to 291 mg kg-1 in the humid-temperate forest. The organic phosphorus content in topsoils was 1.6 to 2.4 times higher in close root proximity (0–2 mm distance to roots) compared to bulk soil (4–6 mm distance to roots) in the Mediterranean woodland and humid-temperate forest, showing intensive phosphorus bioaccumulation in the rhizosphere. Redundancy analysis (RDA) revealed that LMWOAs were explained by the content of hydroxyapatite and variscite phosphorus-species in the arid shrubland, indicating that LMWOAs contribute to mineral weathering in this soil. LMWOA contents, phosphatase activity, and microbial biomass carbon correlated strongly with organic phosphorus in the humid-temperate forest soil, which implies a high relevance of LMWOAs for organic phosphorus recycling. In the Mediterranean woodland soil, however, oxalic acid correlated with organic phosphorus in the topsoil (suggesting phosphorus recycling), whereas in the subsoil malic and citric acid were correlated with primary and secondary phosphorus minerals (implying mineral weathering). We conclude that phosphorus acquisition and cycling depend strongly on climate and that the functions of LMWOAs in the rhizosphere change fundamentally along the precipitation gradient. In the arid shrubland LMWOAs facilitate biochemical weathering (rock eating), while in the humid-temperate forest their functions change towards supporting organic phosphorus recycling (vegetarian).zeige mehrzeige weniger

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Autor*innen:M. Koester, S. C. Stock, F. Nájera, Khaled AbdallahORCiD, Anna GorbushinaORCiD, J. Prietzel, F. Matus, W. Klysubun, J. Boy, Y. Kuzyakov, M. A. Dippold, S. Spielvogel
Dokumenttyp:Zeitschriftenartikel
Veröffentlichungsform:Verlagsliteratur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):Geoderma
Jahr der Erstveröffentlichung:2020
Organisationseinheit der BAM:4 Material und Umwelt
4 Material und Umwelt / 4.0 Abteilungsleitung und andere
Verlag:Elsevier B.V.
Verlagsort:Amsterdam
Jahrgang/Band:388
Erste Seite:114827
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Sanitär- und Kommunaltechnik; Umwelttechnik
Freie Schlagwörter:Biogenic weathering; Climate gradient; Low-molecular-weight organic substances; Organic phosphorus breakdown; Phosphorus K-edge-XANES spectroscopy; Rhizosphere processes
Themenfelder/Aktivitätsfelder der BAM:Umwelt
Umwelt / Umwelt-Material-Interaktionen
DOI:10.1016/j.geoderma.2020.114827
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:28.12.2020
Referierte Publikation:Ja
Datum der Eintragung als referierte Publikation:18.03.2021
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