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Long-Term Effects of Elevated Atmospheric CO2 on Soil Fungi
Rillig, M.C., Hernandez, G.Y. and Newton, P.C.D.  2000.  Arbuscular mycorrhizae respond to elevated atmospheric CO2 after long-term exposure: evidence from a CO2 spring in New Zealand supports the resource balance model.  Ecology Letters 3: 475-478.

What was done
The authors examined several characteristics of arbuscular mycorrhizal fungi associated with the roots of plants growing for at least 20 years along a natural CO2 gradient near a CO2-emmitting spring in New Zealand to determine the long-term effects of atmospheric CO2 enrichment on these beneficial soil fungi.

What was learned
Elevated CO2 significantly increased percent root colonization by arbuscular mycorrhizal fungi in a linear fashion - and by nearly 4-fold! - in going from 370 to 670 ppm CO2.  Similarly, fungal hyphal length experienced a linear increase of over 3-fold along the same atmospheric CO2 gradient; while total soil glomalin (a protein secreted by fungal hyphae that increases soil aggregation and stability) experienced a linear increase of approximately 5-fold.

What it means
As the atmospheric CO2 concentration continues to rise, it is likely that the positive responses of arbuscular mycorrhizal fungi identified in this study will continue to become even more pronounced.  If, for example, less than a doubling of the air's CO2 content has produced 3-, 4- and even 5-fold increases in fungal hyphal length, percent root colonization and total soil glomalin concentrations, respectively, what's to keep further increases in atmospheric CO2 concentration from producing 6-, 7- and 8-fold increases in these parameters?  It would appear that the sky's the limit!  And as these dramatic underground changes continue to occur, soil losses via wind and water erosion should be significantly reduced, due to CO2-induced glomalin-mediated increases in soil aggregate stability, which should benefit terrestrial ecosystems worldwide.