Effects of elevated CO₂ on competition between native and invasive grasses

Area of Science:

• Ecology
• Plant Biology
• Climate Change Research

Background:

• Elevated atmospheric carbon dioxide (CO2) is known to enhance invasive plant performance in monocultures.
• The impact of increased CO2 on the competitive dynamics between invasive and native grasses in mixed stands remains poorly understood.

Purpose of the Study:

• To investigate how elevated CO2 concentrations affect the relative competitive abilities of invasive versus native perennial grasses.
• To determine if increased CO2 levels exacerbate the competitive suppression of native grasses by invasive species.

Main Methods:

• Greenhouse experiment comparing four native and four invasive perennial C3 and C4 grasses under ambient and elevated CO2 (700-1000 ppm).
• Assessed competitive outcomes using measures of relative interaction intensity (biomass allocation) and relative performance of photosynthetic traits.
• Evaluated biomass and tiller production in native-invasive species pairs.

Main Results:

• Elevated CO2 concentrations showed no significant effect on aboveground biomass or tiller production, key measures of interaction intensity.
• Invasive grasses consistently outperformed native grasses in biomass and tiller production across all CO2 treatments.
• Relative performance for most measured photosynthetic traits was not significantly affected by elevated CO2.

Conclusions:

• Increasing atmospheric CO2 concentration alone appears to have minimal impact on the competitive outcomes between invasive and native grasses under controlled conditions.
• The inherent competitive advantages of invasive grasses, rather than CO2 levels, are the primary drivers of dominance in these mixed-species interactions.