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Soil Phosphorus Forms along a Strong Nutrient Gradient in a Tropical Ombrotrophic Wetland
Author(s) -
Cheesman Alexander W.,
Turner Benjamin L.,
Ramesh Reddy K.
Publication year - 2012
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2011.0365
Subject(s) - ombrotrophic , chemistry , phosphorus , soil water , environmental chemistry , phosphomonoesters , peat , podzol , wetland , organic matter , bog , pyrophosphate , nutrient , transect , phosphate , ecology , biology , organic chemistry , biochemistry , enzyme , inorganic phosphate
Phosphorus cycling influences productivity and diversity in tropical wetlands, yet little is known about the forms of P found in the accreting organic matter of these ecosystems. We used alkaline (NaOH–ethylenediamine tetraacetic acid [EDTA]) extraction and solution 31 P nuclear magnetic resonance (NMR) spectroscopy to characterize P in surface soils across a strong nutrient gradient within a tropical ombrotrophic peat dome. From the interior bog plain to the marginal Raphia taedigera swamp, total soil P increased from 14.6 to 70.9 g m −3 and resin‐extractable P from 0.1 to 30 mg kg −1 . Phosphatase activity declined across the same transect (364–46 μmol methylumbelliferone kg −1 min −1 ), indicating an increase in P availability toward the periphery of the wetland. Organic P identified by solution 31 P NMR spectroscopy included phosphomonoesters (12–17%), phosphodiesters (10–14%), and phosphonates (up to 3.3% of total P). Inositol phosphates were not detected in these acidic peats. Inorganic P forms included orthophosphate (9–25% of total P), pyrophosphate (up to 3%), and long‐chain polyphosphates; the latter occurred in concentrations (up to 24% of total soil P) considerably higher than previously found in wetland soils. The concentration of residual (unextractable) P was similar among sites (mean 280 mg kg −1 ), resulting in an increase in its proportion of the total soil P from 29% at the P‐rich margins to 55% at the P‐poor interior. This is the first information on the P composition of tropical wetland soils and provides a basis for further study of the cycling and contribution of P forms to the nutrition of plants and microorganisms.