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Landscape analysis of soil characteristics of 12 forested floodplains in the southeastern US.
Walbridge, Mark*,1, Cade-Menun, Barbara2, Dress, William1, 1 West Virginia University, Morgantown, WV2 Stanford University, Stanford, CA
ABSTRACT- We compared soil characteristics of forested floodplains selected as part of a broader study to analyze phosphorus transformations during flooding events. Soils were collected from 12 floodplains bordering two types of riverine systems (alluvial vs. blackwater), with underlying parent materials of two ages (Young - Pliocene/Miocene - 2-24 millions years old vs. Old - Cretaceous - 66-144 million years old) (n = 3 per river type/parent material combination). Surface soils were collected form all 12 sites during July and August 2002, and analyzed for pH, texture, total C, N, and P, and base cations. Soils were also extracted with EDTA/NaOH, and then analyzed by 31-P NMR. Soil pH averaged 4.7 across all sites. Total C, N, and P concentrations were all significantly greater in soils collected from blackwater vs. alluvial floodplains. Soil N:P ratios ranged from <1 to >13, and were greater in blackwater systems on old parent materials. A significantly greater proportion of P was present as organic P in soils from blackwater vs. alluvial floodplains (59.2 vs. 40.9 %, respectively). Phosphate monoesters were the predominant from of organic P in all soils, comprising 65-89% of total organic P, followed by phosphate diesters (11-31 % of total organic P). Small percentages of pyrophosphates (1-4 % of total P) were found in all soils. Small percentages of phosphonates were found primarily in soils of blackwater floodplains. Results emphasize the importance of considering landscape features (e.g., river type; parent material) when studying P transformations in field experiments.
Key words: blackwater, alluvial, parent materials, phosphorus