THE DYNAMICS OF DISSOLVED NITROGEN IN A BLANKET PEAT DOMINATED CATCHMENT

Precipitation, soil solution and drainage water were collected from a blanket peat catchment at Moor House National Nature Reserve in the No rthern Pennine Uplands, UK, an area of moderately high N deposition. T wo tributaries of the main stream were also sampled. Between 1993 and 1995 samples were analysed for NH4+ and NO3- and for part of the perio d for organic N. Inputs of N in precipitation exceeded outputs in stre am water. Organic N represented a small proportion of N inputs while i nputs of inorganic N averaged 10.2 kg ha(-1) a(-1). Soil solution from 10 cm depth in the peat was dominated by organic N whereas at 50 cm N H4+ slightly exceeded organic N. NO3- was rarely detected at either de pth except during a period of exceptionally warm and dry weather in 19 95. Output fluxes in stream water of organic N (5.7 to 6.5 kg ha(-1) a (-1)) were much greater than those of inorganic N (0.6 to 2.2 kg ha(-1 ) a(-1)). Inorganic N in streams was predominantly NO3- except in the smallest stream which had the largest concentrations of NH4+. This sug gests that N transformations, particularly nitrification, may be takin g place in the mineral soils adjacent to the streams or within the str eam channel of the larger catchment. (C) 1998 Elsevier Science Ltd. Al l rights reserved.