The allometry of root production and loss in seedlings of Acer rubrum (Aceraceae) and Betula papyrifera (Betulaceae): Implications for root dynamics in elevated CO2

Total root production (Sigma P), total root loss (Sigma L), net root production (NP), and biomass production were determined for seedlings of Betula papyrifera and Acer rubrum in ambient and elevated CO2 environments. Sigma P, Sigma L, and NP were calculated from sequential, independent observations of root length production through plexiglass windows. Elevated CO2 increased Sigma P, Sigma L, and NP in seedlings of Betula papyrifera but not Acer rubntm. Root production and loss were qualitatively similar to whole-plant growth responses to elevated CO2. Betula showed enhanced Sigma P. Sigma L, and biomass with elevated CO2 but Acer did not. However, the observed effects of CO2 on root production and loss did not alter the allometric relationship between root production and root loss for either Acer or Betula. Thus, in this experiment, elevated CO2 did not affect the relationship between root production and root loss. The results of this study have important implications for the potential effects of elevated CO2 on root dynamics. Elevated CO2 may lead to increases in root production and in root loss (turnover) where the changes in root turnover are largely a function of the magnitude of root production increases.