Retention of phosphorus in highly weathered soils under a lowland Amazonian forest ecosystem

• Published in: Journal of Geophysical Research - Biogeosciences Vol. 113; no. G4; pp. G04012 - n/a
• Main Authors: McGroddy, M. E., Silver, W. L., de Oliveira Jr, R. C., de Mello, W. Z., Keller, M.
• Format: Journal Article
• Language: English
• Published: Washington, DC American Geophysical Union 01-12-2008; Blackwell Publishing Ltd
• Subjects: Amazon; Bioavailability; Biogeochemical cycles, processes, and modeling; Biogeosciences; chemical speciation and complexation; Earth sciences; Earth, ocean, space; Ecosystems, structure and dynamics; Exact sciences and technology; nutrient additions; nutrient cycles; Nutrients and nutrient cycling; root biomass; seasonality; Soils/pedology; nutrient cycles; Amazon; seasonality; root biomass; nutrient additions; fine-grained materials; Amazonian; Tropical forest; Clay soils; leaching; chemical reactions; clay; sedimentary rocks; ecosystems; erosion; soils; primary productivity; export; loam; retention; clastic rocks; phosphorus
• ISSN: 0148-0227; 2156-2202
• DOI: 10.1029/2008JG000756

The low available phosphorus (P) pools typical of highly weathered tropical forest soils are thought to result from a combination of export of phosphorus via erosion and leaching as well as chemical reactions resulting in physically and chemically protected P compounds. Despite the low apparent P availability, these soils support some of the highest terrestrial net primary productivity globally. We followed different P fractions after P additions to two soil types, sandy loam and sandy clay, over 1 year in a lowland Amazonian forest. Of all the soil P fractions measured, only the NaHCO3 and NaOH extractable fractions showed a significant increase following P additions, and this occurred only in sandy clays (+ 56.9 ± 15.1 kg ha−1 and + 2.8 ± 1.5 kg ha−1, respectively). Our results indicate that intermediate rather than recalcitrant pools are the dominant fate of added P over an annual timescale even in fine‐textured soils. Fine root and forest floor P pools increased more in the sandy loams following P additions suggesting a larger biotic P sink in these soils. Leaching of inorganic P from the surface soils was an unexpected and significant fate of added P in both soil types (9 ± 3% in the sandy loams, 2 ± 1% in the sandy clays). Significantly more of the added P was retained in the sandy clay soils than in the sandy loams (69 ± 20% versus 33 ± 7%) over the 1‐year period.