Impact of land-use change on nitrogen mineralization in subalpine grasslands in the Southern Alps

A field study was conducted to investigate the effect of abandonment of man agement on net N mineralization (NNM) in subalpine meadows. NNM, soil micro bial biomass N (SMBN), fungal biomass and physicochemical 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 t he abandoned area and ranged from 150 to 373 and from 25 to 85 mu g 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 d ifference between abandoned and managed meadow. SMBN showed no difference b etween the investigated sites, whereas ergosterol, a measure of fungal biom ass, increased significantly at the abandoned site. The cumulative NNM was negatively correlated with total organic C, C:N ratio, DOC and ergosterol c ontent, and positively correlated with the NH4+-N content of soil. The decr ease in NNM at the abandoned site may be explained by the lower availabilit y of N in substrates characterized by a high C:N ratio which, together with a decrease in pH in the litter layer, may have increased fungal biomass.