PARENT SESSION
Poster Session # 14: Forest Ecology.

Wednesday, August 6 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Maternal and paternal fecundity of trees growing in an elevated CO₂ atmosphere.

LaDeau, Shannon^*,1, Clark, James¹, ¹ Program in Ecology, Durham, NC

ABSTRACT- Fecundity plays a key role in determining the species composition of forest communities While ecological theory predicts fundamental trade-offs among timing of fecundity, tree longevity, productivity and height, these relationships are not well understood due to the difficulty of estimating fecundity parameters in closed stands. Under elevated atmospheric CO₂ concentrations, the biodiversity of forests will depend on both changes in growth rates that confer competitive advantage to some species over others, and on reproductive success. In addition, although male reproductive effort is often overlooked in estimates of tree fecundity, pollination can be a fundamental limit on seed production. Data presented here are from the FACTS-I site at Duke Forest, NC. Central towers in each of the six rings allow for direct observation of individual tree fecundity. This study demonstrates that loblolly cone and seed production are greatly enhanced by CO₂ fumigation over five years. Elevated and ambient trees both experienced low fecundity in 2001, but re-established the fumigation effect in 2002. Maturation rates are increased in the elevated rings, with 30% of the trees producing both male and female cones in 2002 (vs. 15% in ambient rings). In 2002, more than 40% of the elevated trees produced male strobili, over twice that in the ambient rings. These data suggest that the maturation rate of loblolly pine has been increased under CO₂ fumigation. Changes in ontogeny, as implied by this study, may have important implications for lifespan and tree cycling in forests.

Key words: forest ecology, fecundity, reproductive ecology, carbon dioxide