Soil properties associated with net nitrification following watershed conversion from Appalachian hardwoods to Norway spruce
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- Kelly, C.N., Schoenholtz, S.H. & Adams, M.B. Plant Soil (2011) 344: 361. doi:10.1007/s11104-011-0755-5
Nitrate (NO3-N) in soil solution and streamwater can be an important vector of nitrogen (N) loss from forested watersheds, and nitrification is associated with negative consequences of soil acidification and eutrophication of aquatic ecosystems. The purpose of this study was to identify vegetation-mediated soil properties that may control potential net nitrification dynamics and to determine if net nitrification is a function of abiotic retention or biotic inhibition. We performed a soil inoculation and incubation study and analyzed a suite of soil chemical and biological properties in soils from a 40-year-old Appalachian hardwood forest and an adjacent 37-year-old Norway spruce forest converted from Appalachian hardwoods. Our results indicate that net NO3-N production was nine times higher in hardwood soil (mean = 183.51 mg N/kg/28 days) than in the spruce soil (mean = 18.97 mg N/kg/28 days) and differences in net NO3-N production were attributed to differences in soil substrate quality. Soil properties that were most strongly correlated with NO3-N production across vegetation types included total soil N, soil C:N ratio, oxalate concentration, and sulfate concentration. Establishment of a spruce monoculture in the central Appalachian hardwood ecoregion significantly altered N cycling, likely depleted soil N stores, increased soil acidity, and altered soil organic matter dynamics, thus leading to low net nitrification rates.