What was done
Two perennial grassland species (rhizoma peanut-Arachis glabrata and bahiagrass-Paspalum notatum) native to South America and common to Florida, USA, were grown in greenhouses fumigated with air containing 360 and 700 ppm CO2 for three growing seasons.  In addition, these C3 and C4 grasses, respectively, were simultaneously exposed to air temperatures that ranged from ambient to 4.5°C above ambient.  Thus, the authors studied the effects of elevated CO2 and air temperature on dry matter production in these economically important forage species.

What was learned
Averaged across three growing seasons, elevated CO2 increased dry matter production in rhizoma peanut and bahiagrass by 25 and 15%, respectively.  However, there were no interactive effects of elevated CO2 and temperature on dry mass production in these species.  Nonetheless, air temperatures 4.5°C above ambient increased dry matter production in both species by an average of 13% across all three years.

What it means
As the air's CO2 concentration increases, it is likely that the dry mass production and carbon sequestering abilities of these two forage grasses will increase significantly, regardless of any accompanying increase in air temperature.  Moreover, it is likely that such CO2-induced growth increases will be larger for the C3 rhizoma peanut than for the C4 bahiagrass, as is commonly reported for C3/C4 plant comparisons in the literature.