REGULAR ARTICLE Shift in soil–plant nitrogen dynamics of an alpine–nival ecotone

Abstract We investigated the nitrogen (N) dynamics of an alpine–nival ecotone on Mt. Schrankogel, Tyrol, Austria, in relation to temperature. Natural abundance of 15N was used as a tool to elucidate differences in N cycling along an altitudinal transect ranging from 2,906 to 3,079 m, corresponding to a gradient in mean annual temperature of 2.4 °C. The amount of total soil N, of plant available N and soil C/N ratio decreased significantly with increasing altitude, whereas soil pH increased. Soil δ15N decreased with increasing alti-tude from +2.2 to −2.1 ‰ and δ15N of plant tissues (roots and leaves) decreased from −3.7 to −5.5‰. The large shift in soil δ15N of 4.3 ‰ from the lowest to the highest site suggested substantial differences in N cycling in alpine and nival ecosystems in the alpine nival ecotone investigated. We concluded that N cycling at the alpine–nival ecotone is likely to be controlled by various factors: temperature, soil age and development, atmospheric N deposition and plant competition. Our results furthermore demonstrate that the alpine–nival ecotone may serve as a sensitive indicator of global change