Elevated CO2 enhances growth of energy trees

Quicknote energy crops and CO2 mitigation
Scientists in Italy working on an EU project called the 'European Free Air Carbon dioxide Enrichment experiment on Poplar plantations' ('POPFACE', now 'EUROFACE' > new website) grew three well-watered and adequately fertilized poplar species for energy - Populus alba L. clone 2AS-11 (white poplar), Populus nigra L. clone Jean Pourtet (black poplar), Populus x euramericana clone I-214 (robusta poplar) - for three years at the POPFACE facility in Central Italy near Viterbo, where the air's CO2 concentration was increased by approximately 180 ppm in half of the experimental plots, after which the trees were coppiced (cut to the bases of their stems some 5-8 cm above the ground) and allowed to sprout and grow again for another three years under the same, but even better fertilized, conditions. The results of the first 3-year growth period and of the second 3-year period are as follows:

• fertilization did not affect the growth of the second-rotation trees, "likely because of the high rates of fertilization during the previous agricultural land use," according to the 14 researchers involved with the experiment.
• "In contrast," in their words, "elevated CO2 enhanced biomass production by up to 29%, and this stimulation did not differ between above- and below-ground parts." the net rate of carbon assimilation was "on average for all species stimulated up to 30% during the third year of the second rotation"
• "after 6 years of fumigation, measurements of photosynthetic parameters along the canopy profile could not detect any clear sign of acclimation to elevated CO2" for the three species.

What it means
The scientists conclude that "poplar trees are able to optimally profit from future high CO2 concentrations, provided that they are intensively managed, planted in regions with high incident radiation and supplied with sufficient nutrients and water." Such "high-density poplar coppice cultures," in their opinion, "offer possibilities to mitigate the rise of atmospheric CO2 by producing renewable bioenergy in an economically feasible way, whereby the elevated CO2 stimulation might sustain over several rotation cycles.

The EUROFACE project aims at carrying out the following tasks:

• Coordination of a trans-European research effort in the field of global change interactions with a forest plantation ecosystem.
• Improvement of existing Free Air CO2 Enrichment facility and granting access to a wider scientific community.
• Development of remote sensing technology to assess water consumption and energy balance of plantation forestry systems under present and future climatic conditions.
• Evaluation the amount of carbon being sequestered in the biomass and in the soil of intensive bio-energy forest plantation in relation to various management regimes (coppice vs. single stem, fertilisation, species choice)
• Assessment of relative contribution of increasing atmospheric levels of CO2 and N fertilisation on increased C sequestration in surplus arable land planted with woody crops.

The question now is whether similar research in the tropics on fast growing energy tree species like Eucalyptus will yield similar results. If this is the case, then planting trees for energy is rapidly becoming one of the most straightforward and efficient ways to combat CO2 in the long-run.

Sources:

• Euroface website
• CO2Science.org: Elevated CO2 Enhances the Effectiveness of a Bio-Energy Tree Plantation - August 23, 2006
• Liberloo, M., Dillen, S.Y., Calfapietra, C., Marinari, S., Luo, Z.B., De Angelis, P. and Ceulemans, R. 2005. Elevated CO2 concentration, fertilization and their interaction: growth stimulation in a short-rotation poplar coppice (EUROFACE). Tree Physiology 25: 179-189 [full-text, *.pdf]
• Gail Taylor, Nathaniel R. Street, Penny J. Tricker, Andreas Sjödin, Laura Graham, Oskar Skogström, Carlo Calfapietra, Giuseppe Scarascia-Mugnozza and Stefan Jansson, July 2005. The transcriptome of Populus in elevated CO2, New Phytologist, Volume 167, p. 143 [abstract]

[Entry ends here].
biomass :: bioenergy :: biofuels :: energy :: sustainability :: CO2 :: climate change :: poplar ::