Disturbance plays a large role in shaping ecological communities. Soil communities
in particular are often severely affected by disturbance. However, there is little
evidence which describes how these communities respond to disturbance. Arbuscular mycorrhizal
(AM) fungi are an example of an important soil constituent. Past studies show
that arbuscular mycorrhizal fungi are vulnerable to soil disturbance. This could affect terrestrial
communities in many ways as AM fungi have been shown to be important for ecosystem
functioning and plant community structure. We suspected that AM fungi differ in
their response to soil disturbance due to inherent differences among AM fungal suborders
in life history traits. Specifically, we predicted that AM fungi in the suborder
Gigasporineae, which colonize roots primarily by spores would be more resilient to soil disturbance
than AM fungi in the suborder Glomineae, which colonize roots primarily from
hyphal fragments. We also predicted that the growth of AM fungal host plants would be
greater when associated with AM fungi that were less compromised by soil disturbance.
To test these predictions, we compared the response of AM fungal isolates from the two
suborders to soil disturbance, relative to their response in non-disturbed controls in a
glass-house pot experiment. AM fungal response was measured in terms of % colonization,
root fungal biomass, soil hyphal length, soil ergosterol and spore density. Four different
host plants were used and their growth was measured in terms of total plant biomass
and % foliar phosphorus. Gigasporineae isolates were significantly less affected than
Glomineae isolates by soil disturbance in terms of root colonization, soil colonization and
spore densities. Host biomass was positively correlated with AM fungal response. In contrast,
no difference in host foliar phosphorus content was detected between hosts grown
with Gigasporineae versus Glomineae isolates. These results confirm that AM fungi differ
in their response to soil disturbance. Therefore, the composition of the AM fungal community
will determine the actual effect of soil disturbance on AM fungal-mediated plant
growth.