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 management on net N mineralization (NNM) in subalpine meadows. NNM, soil microbial 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 the 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 difference between abandoned and managed meadow. SMBN showed no difference between the investigated 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 content, and positively correlated with the NH(4)(+)-N content of soil. The decrease in NNM at the abandoned site may be explained by the lower availability 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.