Stable nitrogen isotopes (δ15N) in thalli of the lichen Hypogymnia physodes along a altitudinal gradient in the Khangai Plateau, Mongolia

Stable nitrogen isotopes (??¹⁵N) have been determined in the organic matter (OM) of thalli of the lichen Hypogymnia physodes (L.) Nyl. collected at 15 levels along an altitudinal gradient (1250?C2928 m a.s.l.) in forest and alpine meadow communities of the Khangai Plateau, Mongolia. The results show that, in the study region as a whole, no correlation between the ??¹⁵N content and elevation is observed. However, the lichen OM within the mountain forest belt is depleted of the heavy ¹⁵N isotope as elevation increases (from 1250 to 2400 m a.s.l.), whereas in the alpine meadow belt (2500?C2928 m a.s.l) it is enriched with this isotope. In addition, ??¹⁵N values in OM show an inverse dependence on the relative content of total nitrogen in the thalli.