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

摘要

Background For 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. Results Mean plant δ15N prior to correction was 49‰ and ?5.8‰ under nitrate and ammonium, respectively. Plant δ15N was non-linearly correlated to biomass (r2?=?0.331 and 0.249 for nitrate and ammonium, respectively; P?