Root tissue chemistry, mycorrhizal colonization, and uptake of 15N 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 C and N tissue concentrations and natural abundance isotope signatures, ectomycorrhizal colonization, along with the uptake of 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.