Patterns of Nitrogen Mineralization in Wetlands of the New Jersey Pinelands along a Shallow Water Table Gradient

摘要

Nitrogen dynamics in wetlands are often assumed to vary with water tables and the resulting patterns of soil moisture, and other soil properties. To test this hypothesis, we have examined N mineralization patterns in two replicate sequences of three forested wetland types located on a shallow water table gradient in the New Jersey Pinelands during a 12 my sampling period. Each sequence of the three forested wetlands consists of pine wetlands and pine-hardwood swamps with sandy mineral soils and cedar swamps with peat soils along the shallow water table gradient. Although water tables differed between the two mineral-soil wetlands, there were no differences in soil properties between them, including patterns of extractable N or net N mineralization rate. However, peat soils from the cedar swamps had net N mineralization rate 5-10 times higher than the mineral soils from the other two types of wetlands over the sampling period. Although soil moisture was correlated with water table position within wetlands, net N mineralization rate did not vary with water tables, nor did it vary with soil moisture variations within sites. Overall, net N mineralization rate reflects soil type (histosols vs. mineral hydric soil) and organic matter quality (C:N) ratio.