Rising CO2 levels and the fecundity of forest trees

We determined the reproductive response of 19-year-old loblolly pine (Pinus taeda) to 4 years of carbon dioxide (CO2) enrichment (ambient concentratio n plus 200 microliters per liter) in an intact forest. After 3 years of CO2 fumigation, trees were twice as likely to be reproductively mature and pro duced three times as many cones and seeds as trees at ambient CO2 concentra tion. A disproportionate carbon allocation to reproduction under CO2 enrich ment results in trees reaching maturity sooner and at a smaller size. This reproductive response to future increases in atmospheric CO2 concentration is expected to change Loblolly dispersal and recruitment patterns.