Allometric relations and growth in Pinus taeda: The effect of elevated CO2 and changing N availability


Journal Article

Loblolly pine (Pinus taeda L.) seedlings were grown for 138 d at two CO2 partial pressures (35 and 70 Pa CO2) and four N solution concentrations (0·5, 1·5, 3·5 and 6·5 mM NH4NO3). Allometric regression analysis was used to determine whether patterns of biomass allocation among functionally distinct plant-parts were directly controlled by CO2 and N availability or whether differences between treatments were the result of size-dependent changes in allocation. Both CO2 and N availability affected growth of loblolly pine. Growth stimulation by CO2 at nonlimiting N solution concentrations (3·5 and 6·5 mM NH4NO3) was c. 90%. At the lowest N solution concentration (0·5 mM NH4NO3), total plant biomass was still enhanced by 35% under elevated CO2. Relative growth rates were highly correlated with net assimilation rates, whereas leaf mass ratio remained unchanged under the wide range of CO2 and N solution concentrations. When differences in plant size were adjusted apparent CO2 effects on biomass allocation among different plant parts disappeared, indicating that CO2 only indirectly affected allocation through accelerated growth. N availability, by contrast, had a direct effect on biomass allocation, but primarily at the lowest N solution concentration (0·5 mM NH4NO3). Loblolly pine compensated for N limitation by increasing specific lateral root length and proportional biomass allocation to the lateral root system. The results emphasize the significance of distinguishing size-dependent effects on biomass allocation from functional adjustments made in direct response to changing resource availability.

Full Text

Duke Authors

Cited Authors

  • Gebauer, RLE; Reynolds, JF; Strain, BR

Published Date

  • January 1, 1996

Published In

Volume / Issue

  • 134 / 1

Start / End Page

  • 85 - 93

International Standard Serial Number (ISSN)

  • 0028-646X

Digital Object Identifier (DOI)

  • 10.1111/j.1469-8137.1996.tb01148.x

Citation Source

  • Scopus