How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

Effects of Elevated CO2 and Soil Nitrogen on Sixteen Grassland Species
Reich, P.B., Tilman, D., Craine, J., Ellsworth, D., Tjoelker, M.G., Knops, J., Wedin, D., Naeem, S., Bahauddin, D., Goth, J., Bengtson, W. and Lee, T.A.  2001.  Do species and functional groups differ in acquisition and use of C, N and water under varying atmospheric CO2 and N availability regimes?  A field test with 16 grassland species.  New Phytologist 150: 435-448.

What was done
Sixteen perennial grassland species were grown as monocultures within FACE plots receiving atmospheric CO2 concentrations of 360 and 560 ppm and low and high levels of soil nitrogen for two years to determine the interactive effects of elevated CO2 and soil nitrogen on their growth and development.

What was learned
Interestingly, there were no interactions between atmospheric CO2 concentration and soil nitrogen for any measured plant parameter.  Nonetheless, elevated CO2 increased total plant biomass for forbs, legumes and C3 grasses by 31, 18 and 9%, respectively, while it decreased the growth of C4 grasses by 4%.  Although these CO2-induced increases were smaller than those commonly reported for similar species in CO2-enrichment experiments, the authors felt that plant growth was suppressed even in the high nitrogen treatments due to the inherently low background concentration of nitrogen present in the experimental soils.  In addition, the authors reported that atmospheric CO2 enrichment enhanced soil water contents by 9, 6 and 4% in plots containing C3 grasses, C4 grasses and forbs, respectively, while it had no impact on the soil water content of plots containing legumes.

What it means
As the atmospheric CO2 concentration increases, it is likely that grassland species will exhibit increases in biomass production, due to enhanced uptake of carbon during the process of photosynthesis, regardless of soil nitrogen concentration.  Although CO2-induced growth increases were smaller in magnitude than those commonly reported in the literature, this study demonstrates that grouping plants into categories based on functional photosynthetic and morphological characteristics can prove valuable in broadly determining how a given plant type may respond to future increases in the air's CO2 concentration.  In addition, under future elevated atmospheric CO2 concentrations, it is likely that soil moisture levels beneath grasslands will rise, thus enhancing a number of soil properties in a positive feedback phenomenon that can make the rhizosphere more suitable for microbial activities that can further enhance plant growth.