Effects of Elevated Atmospheric CO₂ on Non-native Plants: Comparison of Two Important Southeastern Ornamentals

Abstract

Understanding how ornamentals will respond to the increasing level of CO₂ in the atmosphere will aid future plant selection. In addition, understanding how rising levels of CO₂ affect the potential of introduced ornamentals to become invasive weeds will be crucial to future management. This study was conducted to determine the effects of elevated CO₂ on growth of two non-native plants commonly used as ornamentals in the southeastern U.S. Lantana (Lantana camara) and vinca (Catharanthus roseus) were grown at either 375μmol mol⁻¹ (ambient) or 575μmol mol⁻¹ (elevated) CO₂ for four months in open top field chambers. Measurements of plant morphology, biomass, and plant tissue nitrogen were made for both species. Lantana growth was more responsive to elevated CO₂ than was vinca. Lantana root and total plant dry weights were increased by 31 and 19%, respectively; in vinca, these values increased by only 9% each. Vinca root length was unaffected by CO₂, however, it was increased by 46% in lantana. Elevated CO₂ had no effect on flower dry weight for either species. This study suggests that rising atmospheric CO₂ will have little impact on vinca as either an ornamental or as a potential invasive weed. Lantana's value as an ornamental may increase due to its abundant growth under elevated CO₂. Lantana's greater root growth may also increase its drought tolerance, adding to its ornamental potential. However, the factors which may make it a more desirable ornamental under future higher CO₂ conditions could also enhance its potential to become a serious invasive weed in the southeastern U.S.