Regulation of organic matter decomposition and nutrient release in a wetland soil

In wetland soils, the supply of O-2 to soil is greatly reduced; thus, alternate electron accepters must be utilized by the microbial populations during decomposition of organic matter. These changes in the supply of electron accepters affect the size of microbial populations, enzyme production, and decomposition of organic matter. A laboratory study was conducted to determine the role of redox potential (Eh) and availability of electron accepters on selected microbial processes regulating organic matter decomposition and nutrient release. Soil Eh was maintained approximately at 620, 310, -100, and -220 mV, with the addition of O-2, NO3-, SO42-, and HCO3-, respectively. The soil microbial biomass, as determined by fumigation-extraction methods, gradually decreased as soils became more reduced. Microbial biomass C ranged from 354 to 10 100 mg C kg(-1) soil (dw), while microbial biomass N and P ranged from 140 to 439 mg N kg(-1) soil (dw), and 64 to 180 mg P kg(-1) soil (dw), respectively. Organic C, N, and P mineralization rates decreased as soils became more reduced. Organic C mineralization rates measured by CO2 production ranged from 51 to 400 mg C kg(-1) (dw) d(-1). Corresponding values of organic N and P mineralization rates ranged from 21 to 150 mg N kg(-1) (dw) d(-1), and 6 to 107 mg P kg(-1) (dw) d(-1), respectively. Significant relationships (P < 0.01) were observed among the soil enzyme activities, microbial biomass, and the mineralization rates of C, N, and P.