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1D - Soil and Sediment Contamination (TUP/5) Natural 15N Abundance in two Nitrogen saturated forest ecosystems at Solling, Germany. Sah, Shambhu1, Brumme, Rainer2, 1 Department of Forest Ecology, Helsinki, Helsinki, Finland2 Institute of Soil Scinece, Goettingen, Lower Sexony, Germany ABSTRACT- This research deals with a comparative study of two different N-saturated forests such as beech and spruce forests at the same location of Solling, Germany. The present results show that 15N natural occurrence in the rainfall (both above and below canopy) at the site of Solling is similar (15N = -15 del to +19 del) to other sites of the world (such as NITREX sites, USA etc.). In the both forests, delta-15N enrichment of both NH4-N and NO3-N showed a decreasing trend of their values from bulk precipitation to upper soil layer, but increasing again in the deeper soil layer. An increase in the 15N enrichment of the soil water from upper soil depth to the lower soil depth has been observed in our study and this has been assumed to be due to the strong net nitrification taking place in the upper layer (organic surface layer) of soil. The mineral soils at the both sites showed characteristic low (negative) delta-15N values in the organic layers, increasing strongly in the mineral soil to positive delta-15N values. In the mineral soil horizons of both stands, an increase in delta-15N values was found, culminating at + 3 to + 5 del in the lower mineral soil. In contrast to mineral soil layer, the presence of almost similar or a slight decrease in delta-15N values with depth within the organic soil layer (0 to 6 cm depth) at both sites indicates the presence of high nitrification rate in this layer, resulting in excessive seepage water NO3-output at the both sites (specially at the spruce site). Key words: Spruce forest, Beech forest, 15N, soil |
