Nitrogen, phosphorus, and carbon mineralization in response to nutrient and lime additions in peatlands

摘要

This objective of this study was to determine if mineralization of C, N, and P was pH stressed and/or nutrient limited in a bog and fen in northeastern Minnesota. Although soil activity in northern peatlands can be limited by low pH, low temperatures, high C:N and C:P ratios of soil organic matter, and/or anaerobic conditions, different classes of peatlands (bog and fen) vary in the type and degree of stress affecting soil processes. We employed in situ studies, laboratory incubations, and a fertilization and liming experiment to understand peatland mineralization dynamics further. Nitrogen mineralization in the field was higher in the fen than in the bog, but net P mineralization was close to zero in both sites. Soil cores were removed from plots that had been treated for 2 years with NH4+, PO4-2, and/or CaCO3, followed by a 30-week lab incubation. Nutrient additions in the bog increased the labile N pool (NO), and cumulative N and P mineralization over 30 weeks, but lime addition had no effect. Nutrient additions to the fen did not significantly alter nutrient pool sizes (N-0, P-0), cumulative mineralization totals, or mineralization rates. However, lime additions decreased potentially mineralizable N and cumulative N mineralization in the fen aerobic incubations, but increased cumulative P mineralization in the anaerobic incubations. Although both are peatlands, bog and fen nutrient cycles are controlled by different factors that may explain the differences in mineralization, total soil N and P, and respective labile pools. This information may be especially useful in anticipating changes brought about by anthropogenic nutrient/cation inputs and hydrologic alterations.