Document: SHA-3-34-20

Reproductive response of Pinus taeda in a Free-Air Carbon Dioxide Enrichment experiment.

LADEAU, S.L.*, J.S.CLARK and I.IBANEZ

Duke University, Durham, NC, USA ¹

Abstract:
A clearer understanding of vegetative response to global carbon dioxide enrichment is critical to predicting future carbon sequestration, community composition and ecosystem regeneration. Few studies have addressed the reproductive response of non-agricultural species to elevated carbon dioxide in a forest setting, yet it is through changes in fitness that plants will respond ecologically and evolutionarily to global change. In this study reproductive response is evaluated in a Pinus taeda stand in the Duke Forest FACTS-I experimental site. Three of six experimental rings maintain an atmosphere at a constant 200 ppm greater than ambient CO₂ concentrations. Cones were rare in this young (19 yr old) stand before CO₂ treatment began, but cone production increased in treatment plots after the first year of CO₂ fumigation. Trees located within elevated CO₂ rings were found to have three times more cones per tree than trees in the control rings (LR test for Poisson Distribution cone abundance; p<.001) and were almost twice as likely to be reproductively mature (p<.001). Intervention analysis, comparing pre- and post treatment numbers of cones per tree, shows a difference over forty times greater for post treatment counts (t=4.1047,df=2,p=.055). Finally, a preliminary analysis of seeds collected from traps in each ring shows that while the total number of seeds collected per ring in 1997 and 1998 was similar for all six rings, the number of seeds collected in 1999 from treatment rings was more than twice the number of seeds collected from control rings.

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This abstract is being presented at: 11:45 AM in session:
Oral Session #40: Elevated CO₂ In Forest Systems.