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Carbon Sequestration in Semi-Arid Grasslands
Reference
Kandeler, E., Mosier, A.R., Morgan, J.A., Milchunas, D.G., King, J.Y., Rudolph, S. and Tscherko, D. 2007. Transient elevation of carbon dioxide modifies the microbial community composition in a semi-arid grassland. Soil Biology & Biochemistry 40: 162-171.

What was done
The authors used open-top chambers to investigate the effects of an elevated atmospheric CO2 concentration (720 vs. 360 ppm) on the composition of the microbial community in the soil of a semi-arid grassland in the shortgrass steppe region of northeastern Colorado (USA) over the last three years of a five-year study.

What was learned
Kandeler et al. report that over the course of their experiment, "the abundance of fungal phospholipid fatty acids (PLFAs) shifted," as the CO2 treatment increased the content of a certain fungal signature molecule by approximately 60% during the final two years of the study, while "in the year after which CO2 enrichment had ceased, abundances of fungal and bacterial PLFAs in the post-CO2 treatment plots shifted slowly back towards the control plots."

What it means
The seven scientists say that "since fungi are unique in their ability to translocate and utilize spatially separated nutrient resources (Poll et al., 2006) and fungi are composed of more complex recalcitrant compounds (Allison et al., 2005), long-term dominance of a fungal-dominated microbial community may result in greater carbon sequestration than in systems with lower fungal abundance (Six et al., 2006)." Consequently, they conclude that the higher abundance of fungi observed in the soil of the CO2-enriched chambers of their study could comprise "a primary mechanism leading to enhanced carbon storage in shortgrass steppe, if elevation of atmospheric CO2 continues in the future."

References
Allison, V.J., Miller, R.M., Jastrow, J.D., Matamala, R. and Zak, D.R. 2005. Changes in soil microbial community structure in a tallgrass prairie chronosequence. Soil Science Society of America Journal 69: 1412-1421.

Poll, C., Ingwersen, J., Stemmer, M., Gerzabek, M.H. and Kandeler, E. 2006. Mechanisms of solute transport influence small-scale abundance and function of soil microorganisms at the soil-litter interface. European Journal of Soil Science 57: 583-595.

Six, J., Frey, S.D., Thiet, R.K. and Batten, K.M. 2006. Bacterial and fungal contribution to carbon sequestration in agroecosystems. Soil Science Society of America Journal 70: 555-569.

Reviewed 20 February 2008