SOIL MICROBIAL RESPONSES TO INCREASED CONCENTRATIONS OF ATMOSPHERIC CO2

Terrestrial ecosystems respond to an increased concentration of atmosp heric CO2. While elevated atmospheric CO2 has been shown to alter plan t growth and productivity, it also affects ecosystem structure and fun ction by changing below-ground processes. Knowledge of how soil microb iota respond to elevated atmospheric CO2 is of paramount importance fo r understanding global carbon and nutrient cycling and for predicting changes at the ecosystem-level. An increase in the atmospheric CO2 con centration not only alters the weight, length, and architecture of pla nt roots, but also affects the biotic and abiotic environment of the r oot system. Since the concentration of CO2 in soil is already 10-50 ti mes higher than that in the atmosphere, it is unlikely that increasing atmospheric CO2 will directly influence the rhizosphere. Rather, it i s more likely that elevated atmospheric CO2 will affect the microbe-so il-plant root system indirectly by increasing root growth and rhizodep osition rates, and decreasing soil water deficit. Consequently, the in creased amounts and altered composition of rhizosphere-released materi als will have the potential to alter both population and community str ucture, and activity of soil- and rhizosphere-associated microorganism s. This occurrence could in turn affect plant health and productivity and plant community structure. This review covers current knowledge ab out the response of soil microbes to elevated concentrations of atmosp heric CO2.