This Figure From Klironomos Et Al 2005 Shows An Experiment Done Over 6 Years The
This figure from Klironomos et al. 2005 shows an experiment done over 6 years. They looked at AMF (mycorrhiza) species richness in ambient CO2 and elevated CO2. For one of the elevated CO2 treatments they increased CO2 to 550ppm abruptly, whereas for the other elevated CO2 treatment, it was a slow gradual increase.