Nitrous oxide fluxes and nitrogen cycling along a pasturechronosequence in Central Amazonia, Brazil

Abstract

We studied nitrous oxide (N₂O) fluxes and soil nitrogen (N) cycling following forest conversion to pasture in the central Amazon near Santarém, Pará, Brazil. Two undisturbed forest sites and 27 pasture sites of 0.5 to 60 years were sampled once each during wet and dry seasons. In addition to soil-atmosphere fluxes of N₂O we measured 27 soil chemical, soil microbiological and soil physical variables. Soil N₂O fluxes were higher in the wet season than in the dry season. Fluxes of N₂O from forest soils always exceeded fluxes from pasture soils and showed no consistent trend with pasture age. At our forest sites, nitrate was the dominant form of inorganic N both during wet and dry season. At our pasture sites nitrate generally dominated the inorganic N pools during the wet season and ammonium dominated during the dry season. Net mineralization and nitrification rates displayed large variations. During the dry season net immobilization of N was observed in some pastures. Compared to forest sites, young pasture sites (

Citation

Wick, B.; Veldkamp, E.; de Mello, W. Z.; Keller, M.; Crill, P. 2005. Nitrous oxide fluxes and nitrogen cycling along a pasturechronosequence in Central Amazonia, Brazil. Biogeosciences, 2, :175–187