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Keywords:

  • calorific value;
  • energy wood;
  • FT-IR;
  • global change;
  • lignin;
  • poplar;
  • Populus

Abstract

To study the influence of elevated CO2 and nitrogen (N) fertilization on wood properties and energy, Populus×euramericana trees were exposed to ambient CO2 (about 370 μmol mol−1 CO2) or elevated CO2 (about 550 μmol mol−1 CO2) using Free Air CO2 Enrichment (FACE) technology in combination with two N levels. Elevated CO2 was maintained for 5 years. After three growing seasons, the plantation was coppiced, one half of each experimental plot was fertilized and secondary sprouts were harvested after two growing seasons. Fourier transform infrared (FT-IR) spectra of wood revealed significant effects of both elevated CO2 and N fertilization on wood chemistry, in particular, significant increases in lignin and decreases in N content. These results were corroborated by chemical analysis. Neither elevated CO2 nor N fertilization affected the calorific value of wood, which was 19.3 MJ kg−1. N fertilization enhanced the energy production per land area by 16–69% because of higher aboveground woody biomass production than on nonfertilized land. Estimates indicate that high yielding poplar short rotation cultivation may significantly contribute as an alternative feedstock for energy production.