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ORGANIC MATTER MANIPULATIONS HAVE LITTLE EFFECT ON GROSS AND NET NITROGEN TRANSFORMATIONS IN TWO TEMPERATE FOREST MINERAL SOILS IN THE USA AND CENTRAL EUROPE
Citation:
HOLUB, S. M., K. LAJTHA, J. SPEARS, S. CROW, J. A. TOTH, M. PAPP, B. A. CALDWELL, AND P. T. NAGY. ORGANIC MATTER MANIPULATIONS HAVE LITTLE EFFECT ON GROSS AND NET NITROGEN TRANSFORMATIONS IN TWO TEMPERATE FOREST MINERAL SOILS IN THE USA AND CENTRAL EUROPE. FOREST ECOLOGY AND MANAGEMENT. Elsevier Science Ltd, New York, NY, 214(1-3):320-330, (2005).
Description:
Soil nitrogen transformations are intricately linked to carbon transformations. We utilized two existing organic matter manipulation sites in western Oregon, USA and Hungary to investigate these linkages. Our questions were: 1) Does the quantity and quality of organic matter affect net and gross N processing in mineral soil? 2) Do these effects vary under high versus low atmospheric N deposition? The organic matter manipulations had a small if any effect on gross and net N cycling rates and N pool sizes. Gross N cycling rates under low N deposition increased with increasing soil C and N, but C:N ratio had no correlation with gross N cycling rates. Soil ammonium concentrations under high N deposition, however, were higher in the organic matter manipulation plots without roots and lower in plots with double litter, indicating a tree root effect and a litter immobilization effect, respectively, but did not differ significantly under low N deposition. Net ammonium production was lower in the litter removal and root removal plots and highest in the litter addition plots at both sites. Gross and net N cycling rates and mineral nitrogen pool sizes were generally higher under higher N deposition and lower C:N ratio soil, which was consistent with past studies over gradients of N deposition. By looking at organic matter manipulations under two very different N deposition scenarios we gained some insight into the role that C:N ratio as well as total C and total N have in controlling N and C cycling in forest soils.