Variation in microbial biomass and activity in four different wetland types

Functional evaluation of wetlands in nutrient cycling, water quality maintenance, and wetland construction and restoration contexts requires knowledge of differences in microbial processes between different wetland types and understanding of the nature and extent of variation in these processes within a given wetland type. In this study, we measured a suite of microbial variables (microbial biomass C and N content, denitrification enzyme activity, potential net N mineralization and nitrification, and soil respiration) that are indices of wetland nutrient cycling and water quality maintenance functions in four different wetland types (calcareous fens, red maple swamps, woodland pools, and wet clay meadows) in eastern New York state. Total soil C and N content, water content, pH, water-table levels, and groundwater NH4+, NO3-, and electrical conductivity were also measured. The clay meadow wetlands were drier and had lower levels of organic matter and most microbial variables than the other wetland types. Site-to-site variation within the fens was very high and was not strongly controlled by water-table levels. Organic matter content and N status appear to be strong regulators of microbial biomass and activity in fens. Red maple swamps and woodland pools had similar levels of most microbial variables. Variation within these wetland types was controlled by hydrology and organic matter quality. The suite of microbial variables that we measured Identified potential functional differences between wetland types and should be useful for comparisons of the water quality maintenance value of different wetlands and for functional evaluation of altered or restored sites.