Quantifying remobilization of pre-existing nitrogen from cuttings to new growth of woody plants using 15N at natural abundance

摘要

BackgroundFor measurements of nitrogen isotope composition at natural abundance, carry-over of pre-existing nitrogen remobilized to new plant growth can cause deviation of measured isotope composition (δ¹⁵N) from the δ¹⁵Nof newly acquired nitrogen. To account for this problem, a two-step approach was proposed to quantify and correct for remobilized nitrogen from vegetative cuttings of Populus balsamifera L. grown with either nitrate (δ¹⁵N = 58.5‰) or ammonium (δ¹⁵N = −0.96‰). First, the fraction of carry-over nitrogen remaining in the cutting was estimated by isotope mass balance. Then measured δ¹⁵N values were adjusted for the fraction of pre-existing nitrogen remobilized to the plant.