Aboveground inventory of sour orange trees exposed to different atmospheric CO 2 concentrations for 3 full years

Abstract

Sour orange trees have been grown from the seedling stage out-of-doors at Pheonix, Arizona in clear-plastic-wall, open-top enclosures for 3.5 years. For the last 3 years of this period, half of the trees have been continuously exposed to air enriched with an extra 300 cm 3 of CO 2 m −3 of air. Inventories of all aboveground plant parts conducted at the conclusions of the second and third years of the study reveal that the total number of branches per tree, the total number of leaves per tree, and the total trunk plus branch volume per tree can all be adequately inferred from measurements of trunk cross-sectional area. They also reveal a sustained beneficial impact of atmospheric CO 2 enrichment. After 3 full years of differential CO 2 exposure, the CO 2-enriched trees had nearly 100% more branches, 75% more leaves, approximately 160% more trunk and branch volume, and 190% more trunk, branch and fruit rind volume than the ambient-treatment trees.