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 375 μmol mol−1 (ambient) or 575 μmol 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.