Nitrogen dynamics in different types of pasture in the Austrian Alps |
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Authors: | E Hackl S Zechmeister-Boltenstern E Kandeler |
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Institution: | (1) Institute for Forest Ecology, FBVA Federal Forest Research Centre Vienna, Seckendorff-Gudent-Weg 8, 1131 Vienna, Austria e-mail: evelyn.hackl@fbva.bmlf.gv.at Tel.: +43-1-878381305 Fax: +43-1-878381250, AT;(2) Institut für Bodenkunde und Standortslehre, University of Hohenheim, 70593 Stuttgart, Germany, DE |
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Abstract: | Soil N dynamics were compared in Alpine pastures on two mountains. N-pool sizes and N fluxes were measured relative to N
losses via leaching and denitrification in summer. On each mountain, four types of pasture were studied: (1) forest pastures,
(2) recently developed pastures formed by forest clearance ("new pastures"), (3) older established pastures, and (4) pastures
planted with clover. At both study sites (Scheuchegg and Teufelstein) we obtained similar results. Compared with forest pasture
soils, open pasture soils were found to have greater microbial biomass and faster mineralisation potentials, but net field
mineralisation rates were slower. In the forest pastures, highest N losses via denitrification were found. Higher potential
leaching of NO3
–, estimated by accumulation of NO3
– on ion-exchange resins, in the forest pasture soils suggests lower N uptake by microbes and herbaceous plants compared with
open pastures. N2O-production rates of the forest pasture soils at the Scheuchegg site (11.54 μg N2O-N m–2 h–1) were of similar magnitude to those reported for spruce forests without pastures, but at Teufelstein (53.75 μg N2O-N m–2 h–1) they were higher. However, if forest pastures are not overgrazed, no elevated N loss through N2O production and leaching of NO3
– is expected. Denitrification rates in the open pastures (0.83–7.50 μg N2O-N m–2 h–1) were low compared with reports on lowland pastures. In soils of the new pastures, rates of microbial N processes were similar
to those in the established pastures, indicating a high capacity of soils to restore their internal N cycle after forest clearance.
Received: 19 August 1999 |
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Keywords: | Alpine pastures Denitrification Ion-exchange resins Microbial biomass Nitrogen cycling |
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