Biological processes dominate phosphorus dynamics under low phosphorus availability in organic horizons of temperate forest soils

• Published in: Soil biology & biochemistry 2018-11, Vol.126, p.64-75
• Main Authors: Pistocchi, Chiara, Mészáros, Éva, Tamburini, Federica, Frossard, Emmanuel, Bünemann, Else Katrin
• Format: Article
• Language: English
• Subjects: 33P; Earth Sciences; Geochemistry; Isotopic dilution; Life Sciences; Litter addition; Mineralization; Radioisotope tracing; Sciences of the Universe; Sequential extraction; Vegetal Biology
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2018.08.013

Understanding the mechanisms underlying phosphorus (P) availability is important to predict forest productivity in a changing environment. We quantified P fluxes and traced P from plant litter into inorganic and organic soil P pools in organic horizons from two contrasting temperate forest soils with low and high inorganic P availability, respectively. We incubated the two organic horizons with and without litter after labelling the soil solution with 33P and performed sequential extractions at several time points in order to trace P dynamics in labile (water-extractable, available and microbial P) and non-labile (non-living organic P, P bound to iron and aluminium and P bound to calcium) pools. Under low P availability, P fluxes were dominated by gross P mineralization, and microbial P immobilization accounted for up to 95% of gross P mineralization. Additionally, labile P in plant litter was rapidly incorporated into microbial P and only a small fraction ended up in the non-labile inorganic P pools. In contrast, P fluxes under high P availability were dominated by abiotic processes, particularly by fast (within 10 days) sorption/desorption reactions between the available P and the P bound to aluminium. These findings support the hypothesis that under low P availability biological processes control P fluxes. The observed tight cycling of P, with little efflux due to net P mineralization, suggests that the mineralization of organic P is driven by microbial P demand, and that the microbial community could compete with plants for available P. [Display omitted] •We measured phosphorus pools and fluxes in two organic horizons from forest soils.•Under low P availability, biological fluxes dominate phosphorus availability.•Under low P availability, microbial immobilization is the main flux.•P from plant litter is rapidly incorporated into microbial P under low P availability.•Under high P availability, fast sorption/desorption exchanges prevail.