What was done
Loblolly pine (Pinus taeda) seedlings were grown in glasshouses receiving atmospheric CO2 concentrations of 350 and 700 ppm for five months.  In addition, seedlings were subjected to four different soil nitrogen regimes to study the interactive effects of elevated CO2 and soil nitrogen on tissue concentrations of carbon-based secondary compounds in this species.

What was learned
Elevated CO2 increased above- and belowground concentrations of total phenolics in seedlings by about 21 and 35%, respectively, when averaged across all nitrogen treatments.  There were no significant interactions between atmospheric CO2 and soil nitrogen.

What it means
As the air's CO2 content rises, it is likely that loblolly pine seedlings will exhibit enhanced rates of photosynthesis, regardless of soil nitrogen status.  Consequently, this phenomenon should allow for increased synthesis of secondary carbon compounds, which play an important role in plant defensive and resistance mechanisms to herbivores and pathogens.  Thus, it is likely that loblolly pine forests may increase their robustness, health, and longevity, as the atmospheric CO2 concentration continues to rise.