As atmospheric CO₂ levels continue to rise, whether we can rely on forests as carbon sinks (45% of terrestrial carbon) depends on our ability to understand the dynamics behind terrestrial and atmospheric interactions. One concern is the increase in abundance, size, and dominance of native lianas (woody climbing vines) in tropical and temperate forests. Lianas are associated with an increased risk of tree mortality, and may alter forest species composition by disproportionately colonizing certain groups of tree species. Moreover, higher CO₂ could substantially escalate the growth of lianas in low-light understories compared to high-light forest gaps, increasing the success of lianas reaching the canopy. We investigated the growth response of a dominant temperate liana species to increased carbon dioxide under varying light and precipitation levels. The north temperate liana, Parthenocissus quinquefolia, was grown in open-top chambers at either ambient (390ppm) or twice-ambient (780ppm) CO₂ concentrations for seven weeks at the University of Michigan Biological Station. Light levels were manipulated to simulate forest gap or understory light conditions, and each plant received a high, medium, or low soil moisture level.

Results/Conclusions

Elevated CO₂ led to a significant increase in total plant biomass, stem length, and biomass allocation to leaves and stems. However, a reduction in specific leaf area (cm²/g) was also observed under elevated CO₂. There were no significant interactions between CO₂ and the light or water treatments. Results show that P. quinquefolia has a significant positive growth response to elevated levels of CO₂. The extent to which this response will lead to increases in the relative dominance of P. quinquefolia in north temperate forests should be subject to further investigation. This study adds to the limited number of temperate liana species (n=7) grown under elevated CO₂.