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Title: ATMOSPHERIC CARBON DIOXIDE, IRRIGATION, AND FERTILIZATION EFFECTS ON PHENOLIC AND NITROGEN CONCENTRATIONS IN LOBLOLLY PINE (PINUS TAEDA L.) NEEDLES

Author
item Booker, Fitzgerald
item MAIER, CHRISTOPHER - USDA-FOREST SERVICE

Submitted to: Tree Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2000
Publication Date: 6/1/2001
Citation: Booker, F.L., Maier, C. 2001. Atmospheric carbon dioxide, irrigation, and fertilization effects on phenolic and nitrogen concentrations in loblolly pine (Pinus taeda L.) needles. Tree Physiology 21:609-616.

Interpretive Summary: The increasing concentration of atmospheric carbon dioxide due to the burning of fossil fuels worldwide is expected to affect both agriculture and forests. In many plants, elevated atmospheric carbon dioxide will stimulate growth, but it also will change their chemical makeup. Plant chemistry is an important factor in assessing plant quality as well as affecting plant-pest relationships and ecosystem nutrient cycling. In this experiment, branches of loblolly pine trees were treated with either ambient or up to twice ambient concentrations of atmospheric carbon dioxide for two years. We found that elevated carbon dioxide increased the concentration of phenolic compounds such as proanthocyanidins (tannins) and decreased nitrogen content in loblolly pine needles. The results indicated that elevated carbon dioxide and low soil fertilization affected foliar chemical composition, which could in turn affect plant-pathogen interactions, decomposition rates and mineral nutrient cycling.

Technical Abstract: Concentrations of phenolic compounds and nitrogen were measured in loblolly pine (Pinus taeda L.) needles exposed in branch chambers for two years to either ambient or up to twice ambient carbon dioxide concentrations. The carbon dioxide treatments were superimposed on trees treated in combination with irrigation and fertilization for seven years. In addition, the effect of chamber design (branch versus open-top) on needle chemistry was compared. Levels of total soluble phenolics, catechin and proanthocyanidins (tannins) were about 11% higher in needle extracts from the elevated carbon dioxide treatments. There were no significant treatment effects on foliar lignin concentrations. Nitrogen concentrations were about 10% lower in needles from the elevated carbon dioxide treatments. Soil amendment treatments generally had no significant effects on needle phenolic concentrations. In contrast, N concentrations were 23% higher in needles from the fertilization treatments. Treatment effects on proanthocyanidin and N concentrations were similar between branch and open-top chambers. The results indicated that elevated carbon dioxide and low soil fertilization affected foliar chemical composition, which could in turn affect plant-pathogen interactions, decomposition rates and mineral nutrient cycling.