Changes in Al and Fe crystallinity and P sorption capacity in a flood-plain forest soil subjected to artificially manipulated flooding regimes in field mesocosms

Changes in noncrystalline Fe and P sorption capacity in soils subjected to flooding and draining for rice cultivation sparked interest in how periodic flooding in natural riparian wetlands influences soil chemistry and P retention. We examined monthly changes in soil oxalate-extractable Al and Fe, NaOH-extractable Al, DCB-extractable Fe, and P sorption capacity as a function of flooding regime in artificially manipulated field mesocosms installed in a floodplain forest along the Ogeechee River, near Savannah, GA. We hypothesized that: (1) flooding would cause increases in both oxalate-extractable (noncrystalline) Al and Fe concentrations and P sorption capacity, and, (2) this effect would be augmented by increased flooding duration and periodicity. Flooding resulted in increases in oxalate-extractable Al in flooded-drained and periodically flooded soils, decreases in crystalline Fe in all flooding treatments, and an increase in P sorption capacity in flooded-drained soils. However, consistent trends were not observed across all treatment regimes. Potential confounding factors include a lack of synchronicity of experimental and natural flooding cycles, spatial variability of soil chemistry, and increased soil wetness in the treatment field, variables that should be considered in future attempts at elucidating relationships between flooding, soil chemistry and wetland function.