Competition for tracer ¹⁵ N in tussock tundra ecosystems

Abstract

The objectives of this study were to assess the roles of plant species, time, and site on competition for tracer 15 N (without carrier) in tussock tundra ecosystems. Six experimental sites were located in northern Alaska. After one year across the experimental sites, the recovery of 15 N by litter (11.3–16.3%) and mosses (5.4–16.4%) was significantly greater than for aboveground vascular plants (2.6‐5.0%). 15 N recoveries by tundra vascular plants (2.6–5.0%) were low when compared to forest trees (9–25%) which suggest that competition for nitrogen is particularly severe in these cold‐dominated tundra ecosystems. There were no significant differences among sites in 15 N recoveries by vascular plants, by mosses, or by litter. There was a statistically significant decline in 15 N recovery with time for Vaccinium vitis‐idaea and Eriophorum vaginatum between the second and third year. The shallow rooted Vaccinium vitis‐ideae was more highly labeled than the deep rooted Eriophorum vaginatum . Nearness to the source of the applied 15 N played a critical role in competition for surface applied nitrogen.