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| Titel |
Microbial processes dominate P fluxes in a low-phosphorus temperate forest soil: insights provided by 33P and 18O in phosphate |
| VerfasserIn |
Chiara Pistocchi, Federica Tamburini, Else Bünemann, Éva Mészáros, Emmanuel Frossard |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250131842
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| Publikation (Nr.) |
 EGU/EGU2016-12288.pdf |
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| Zusammenfassung |
| The classical view of the P cycle in forests is that trees and mycorrhizal fungi associated with
them take up most of their phosphorus as phosphate (P) from the soil solution. The soil
solution is then replenished by the release of P from sorbed phases, by the dissolution of P
containing minerals or by biological mineralization and/or enzymatic hydrolysis of organic P
compounds. Direct insight into the processes phosphate goes through at the ecosystem level
is, however, missing.
Assessing the relevance of inorganic and biological processes controlling P cycling requires
the use of appropriate approaches and tracers. Within the German Priority Program
“Ecosystem Nutrition: Forest Strategies for limited Phosphorus Resources” we
studied P forms and dynamics in organic horizons (Of/Oh) of temperate beech
forest soils in Germany with contrasting soil P availability (P-poor and P-rich). We
followed the fate of P from the litter into the soil pools, using isotopes as tracers
(stable oxygen isotopes in water and phosphate and 33P) and relied on measurements
in experimental forest sites and a three-months incubation experiment with litter
addition.
Using an isotopic dilution approach we were able to estimate gross (7 mg P kg−1 d−1 over
the first month) and net mineralization rates (about 5 mg P kg−1 d−1 over the first 10 days) in
the P-poor soil. In this soil the immobilization of P in the microbial biomass ranged from 20
to 40% of gross mineralization during the incubation, meaning that a considerable part
of mineralized P contributed to replenish the available P pool. In the P-rich soil,
physicochemical processes dominated exchangeable P to the point that the contribution of
biological/biochemical processes was non-detectable.
Oxygen isotopes in phosphate elucidated that organic P mineralization by enzymatic
hydrolysis gains more importance with decreasing P availability, both under controlled and
under field conditions.
In summary, microbial processes dominated P fluxes (70 to 80%) in the P-poor soil, while in
the P-rich soil microbial processes could not be detected because of the higher
baseline of physicochemical processes. Our results support the hypothesis that
organic P has a faster turnover under conditions of low P availability and that net
mineralization is the most relevant process providing available P for plants under these
conditions. |
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