Root tissue chemistry, mycorrhizal colonization, and uptake of nitrogen-15 tracer in glycine, ammonium, and nitrate form across a tree density gradient in northeastern Siberia. 2017.

Greater tree density and forest productivity at the tundra-taiga ecotone (TTE) are expected with climate warming, with potential feedbacks to the climate system. Yet, competition for nitrogen (N) may impact TTE dynamics. Greater tree density will likely increase N demand, while reducing N supply through soil shading and slower decomposition rates. We explored whether characteristics of roots and root-associated fungi important to N acquisition responded to changes in density at the TTE. We characterized carbon (C) and N tissue concentrations and natural abundance isotope signatures, ectomycorrhizal colonization, along with the uptake of nitrogen-15 (15N) enriched tracers in glycine, ammonium, and nitrate form by excised fine roots of Cajander larch (Larix cajanderi) from 10 stands arrayed across a tree density gradient at the taiga-tundra ecotone in far northeastern Siberia.