Document: JEN-3-35-16

Variation in biomass increase of understory saplings exposed in situ to elevated CO₂,

HARTZ-RUBIN, J.S.* and E.H.DELUCIA

University of Illinois, Urbana, IL 61801, USA ¹

Abstract:
Tree species that have indeterminate growth may have larger growth enhancements in elevated compared to ambient atmospheric CO₂. We measured annual growth of six species of understory deciduous saplings in an intact forest exposed to Free-Air CO₂ Enrichment from 1996 through 1999. Stem length and basal diameter were measured five times over three years in ambient (~36 Pa) and elevated (~56 Pa) CO₂ experimental plots. Biomass was estimated from allometric equations. We found that different species responded differently to elevated CO₂. For example, sweetgum (indeterminate; Liquidambar styraciflua) grew 8% more and red maple (determinate; Acer rubrum) grew 6% less in elevated compared to ambient CO₂. The growth of winged elm (Ulmus alata) did not differ between CO₂ treatments. Based on these results, we predict that the continuing increase in atmospheric CO₂ will favor species with indeterminate relative to determinate growth forms, thus altering forest composition.

Keywords: atmospheric CO₂, growth, indeterminate

This abstract is being presented at: 9:30 AM in session:
Oral Session #40: Elevated CO₂ In Forest Systems.