Biol Fertil Soils (2000) 31 : 441–448 Q Springer-Verlag 2000 V. Zeller (Y) 7 U. Tappeiner European Academy of Bolzano, Domplatz 3, 39100 Bozen, Italy e-mail: vzeller6dnet.it Tel.: c39-0471-306031 Fax: c39-0471-306099 V. Zeller Biologisches Labor der Landesagentur für Umwelt und Arbeitsschutz, Unterbergstrasse 2, 39155 Leifers, Italy M. Bahn, U. Tappeiner Institute of Botany, Department of Ecology, University of Innsbruck, Sternwartestrasse 15, 6020 Innsbruck, Austria M. Aichner Research Centre for Agriculture and Forestry Laimburg, Pfatten, 39040 Auer, Italy ORIGINAL PAPER Valentina Zeller 7 Michael Bahn 7 Meinhard Aichner Ulrike Tappeiner Impact of land-use change on nitrogen mineralization in subalpine grasslands in the Southern Alps Received: 8 January 1999 Abstract A field study was conducted to investigate the effect of abandonment of management on net N mi- neralization (NNM) in subalpine meadows. NNM, soil microbial biomass N (SMBN), fungal biomass and phy- sicochemical characteristics (total C, total N, dissolved organic carbon (DOC) and pH) were determined in surface (0–10 cm) soil from May to October 1997 in an intensively managed and an abandoned meadow at 1770 m a.s.l.. The cumulative NNM was lower in the abandoned area and ranged from 150 to 373 and from 25 to 85 mg N g –1 soil in the intensively managed and the abandoned areas, respectively. The total organic C increased in the abandoned area, while total N showed no difference between abandoned and managed mead- ow. SMBN showed no difference between the investi- gated sites, whereas ergosterol, a measure of fungal biomass, increased significantly at the abandoned site. The cumulative NNM was negatively correlated with total organic C, C : N ratio, DOC and ergosterol con- tent, and positively correlated with the NH 4 c -N content of soil. The decrease in NNM at the abandoned site may be explained by the lower availability of N in sub- strates characterized by a high C : N ratio which, togeth- er with a decrease in pH in the litter layer, may have increased fungal biomass. Key words Land-use change 7 Subalpine meadows 7 Net N mineralization 7 Soil microbial biomass N 7 Ergosterol Introduction Traditionally managed meadows are an essential ele- ment in forming the cultural landscape of the Alps. Over the past few decades, land-use change has led to the abandonment of many traditionally managed subal- pine meadows. As a result, plant species composition has changed, and an invasion of dwarf shrubs has oc- curred in previously managed grasslands (Cernusca et al. 1992; Tappeiner et al. 1999). These changes in plant species composition may be associated with changes in the availability of N for plants (Cernusca et al. 1999b). Besides N inputs by fertilizer applications, plant-availa- ble N depends mainly on the net N mineralization (NNM) activity of soils (Runge 1983). In this process the quality of substrates, as well as the size and commu- nity structure of soil microbial biomass, seems to play a key role in determining the NNM activity in soils (Olff et al. 1994; Scott and Binkley 1997; Burket and Dick 1998). Thus, changes in management practice, which af- fect substrate quality and soil microbial biomass, are as- sumed to significantly alter the NNM activity of soils. NNM may be altered with abandonment of manage- ment due to changes in litter quality caused by a shift in plant species composition. In the abandoned area the presence of dwarf shrubs, containing large amounts of lignin and polyphenols, and reduced leaf N concentra- tions (Bahn et al. 1994, 1999b) may cause a decrease in litter quality. Changes in litter quality lead to changes in soil organic matter composition, which is linked to N mineralization (Hassink 1994). Rasmussen et al. (1998) reported that N mineralization increased with total soil N content of soil organic matter. However, Gonzalez- Prieto et al. (1992) found that N mineralization was not necessarily linked with total soil N, as only specific frac-