Like many of you, we have a Christmas tree here decorated with candy canes with a cute little coal train running around the base. The smell of pine is terrific and we are looking forward to eating the candy canes after the holidays. We are all planning a great holiday season and we are looking forward to a bright future. We hope you and your family share our optimism during this fun time of the year.
Today, we will turn out attention to the state of affairs for the tree and the candy canes, and we searched the literature for any updates on how pine trees and sugar cane will fare in a world of elevated atmospheric carbon dioxide (CO2) levels. Given that the literature contains literally thousands of articles on the positive effects of elevated CO2 on plants, we were optimistic that recent material could be found. Of course, three articles were located within minutes dealing with elevated CO2, pine trees, and sugarcane.
A team of scientists associated with the University of Florida state that “Sugarcane (Saccharum officinarum L. cv. CP73-1547) was grown in Gainesville, Florida (29°38’N and 82°22’W) under field-like conditions for sunlight in paired-companion, temperature-gradient greenhouses.” Some of the greenhouses had ambient atmospheric CO2 concentrations near 360 ppm while other greenhouses had atmospheric CO2 maintained at 720 ppm. At final harvest, the leaf area of the ambient CO2 plants was found to be 34.1 square decimeters per plant, but for the double-CO2 plants, leaf area was 44.5 square decimeters per plant. The elevated CO2 increased the leaf area by over 30 percent! Similarly, leaf fresh weight increased from 165.0 grams per plant to 187.0 grams per plant (a 13% increase). The stem fresh weight increased from 437.3 grams per plant to 680.3 grams per plant (a 56% increase). The above ground mass of the plant increased from 602.0 grams per plant to 867.0 grams per plant (a 44% increase). The all important juice from the main stem increased from 95.0 cubic centimeters to 174.3 cubic centimeters (a whopping 83% increase) all due to the doubling of atmospheric CO2.
Can the news for the sugar canes get any better? Yes, for Vu et al. report “Elevated-CO2 plants also had up to 51% lower stomatal conductance and 39% less transpiration, which resulted in 26–52% greater water-use efficiency (WUE) than ambient-CO2 plants, during leaf growth and development.” In the final sentence of the abstract they conclude that beneficial changes in the biochemistry of the plants “together with a reduction in leaf stomatal conductance and transpiration and an improvement in leaf WUE and plant water status, could lead to an enhancement in leaf area, plant biomass accumulation and sucrose production for the CO2-enriched sugarcane plants.” Basically, thanks to elevated CO2, the sugarcane plants were bigger, they increase sucrose production, and they did so while becoming more water use efficient. We asked the candy canes what they thought of this article, and they said “Sweet!”
Hundred of articles have already shown that pine trees will grow larger, more resistant to drought and other stresses, and more water-use efficient thanks to elevated atmospheric CO2, so we looked around for some other theme, and we found it! Shannon LaDeau and James Clark of Duke University examined results from a 13-year old loblolly pine plantation in the Duke Forest of North Carolina. In August of 1996, equipment was installed in the forest to elevate atmosphere CO2 by 200 ppm for selected groups of trees while other trees continued to grow at ambient atmospheric CO2 levels. In the first of two papers, LaDeau and Clark focused on tree fecundity (ability to reproduce) in terms of cone and seed production. In their own words, they report “Trees in the elevated CO2 plots produced twice as many cones (4063 cones observed) between 1998 and 2004 as trees in the ambient plots (2070 cones) for 262 and 295 sample trees, respectively.” Furthermore, “Fecundity was higher in the elevated plots compared with ambient plots in the early years and remained relatively consistent throughout the study”. They conclude “We found that trees growing under elevated CO2 matured earlier and produced more seeds and cones per unit basal area than ambient grown trees.”
In a second paper, the duo turned their attention to pollen production from these same loblolly pine trees. They report “We find that P. taeda stands grown at high CO2 produce more pollen per unit woody basal area than ambient-grown trees. Trees fumigated with CO2 began producing pollen at younger ages and smaller sizes; thus evenly aged stands had larger proportions of trees contributing pollen under elevated CO2.” Finally, they note that the “earlier onset of reproductive maturation means increased numbers of pollen-producing trees in high-CO2 plots and greater pollen production at the stand level.” And before any of you pollen Scrooge’s play the human health card, LaDeau and Clark point out that “Pine pollen is not a dangerous allergen for the public at large.”
There is no doubt that 2007 will produce many more articles on the biological benefits of elevated CO2 and no end of articles in the literature with results inconsistent with more popular presentations of the global warming issue. Stay tuned here at World Climate Report, but take some time out and enjoy the holidays as much as pine trees and sugar cane enjoy elevated CO2!
LaDeau, S.L. and J.S. Clark, 2006. Elevated CO2 and tree fecundity: the role of tree size, interannual variability, and population heterogeneity. Global Change Biology, 12, 822–833.
LaDeau, S.L. and J.S. Clark, 2006. Pollen production by Pinus taeda growing in elevated atmospheric CO2. Functional Ecology, 20, 541–547
Vu, J.C.V., L.H. Allen, Jr., and R.W. Gesch, 2006. Up-regulation of photosynthesis and sucrose metabolism enzymes in young expanding leaves of sugarcane under elevated growth CO2. Plant Science, 171, 123–131.