Phosphorus Dissolution in the Rhizosphere of Bald Cypress Trees in Restored Wetland Soils.

Phosphorus release to ground or surface waters has been observed in wetlands restored from farmland. This study examined whether rhizospheres of bald cypress (Taxodium distichum L.) are a source of increased P dissolution compared with the soil matrix. The study was conducted in root-box rhizotrons filled with mineral and organic soil materials (Aeric Alaquods and Terric Haplosaprists, respectively) from a Carolina bay wetland restored from row crop agriculture. Rhizotrons were planted with bald cypress saplings or left unplanted to simulate rhizosphere and matrix conditions, respectively. ponding was imposed for 128 d. Soil pore water was sampled in three layers (0-22, 22-41, and 41-59 cm) in each rhizotron twice monthly for dissolved total and reactive p, dissolved organic C (DOC), Fe2+, and redox potential (eh). manual root counts monitored growth and death monthly. Root death was most prevalent at 41 to 59 cm, while vigorous root growth was observed near the surface. The rhizosphere treatments exhibited increased Fe2+ dissolution and increased concentrations of DOC relative to matrix conditions; however, no corresponding P increase occurred. near the surface, rhizosphere P concentrations declined below matrix concentrations after 60 d of ponding. our results show that the rhizosphere of bald cypress did not cause higher P concentrations than matrix values for mineral and organic soils with 3.5 and 19.5% C, respectively. in addition, root growth near the surface resulted in more oxidizing conditions and/or plant uptake of P, which decreased p concentrations below matrix values. [ABSTRACT FROM AUTHOR]