Different responses of fungi and bacteria to environmental
stresses
The ratio of the whole pool of plants to bacterial OTUs in the community
(Fig 3a) paralleled the trend in
total fungal OTUs to plant species (Fig 3b). According to the results of
PICRUSt2, the functional guild assemblage of bacterial OTUs that were
associated with plant species were dominated by carbon fixation and
oxidative phosphorylation(Fig S7b), all of which are associated with
energy metabolisms (Eida et al. 2018). Therefore, we suggest that
soil bacteria communities may play a pivotal role in plant colonization
in stressful environments by providing more available energy.
The findings of this study are of general interest as a novel
perspective on how plant-microbial interactions may vary along
environmental gradients, a broad and far reaching topic with many
implications for ecosystem function. It would be very interesting to see
if the same trends hold true along environmental or plant community
gradients in other main ecosystems, such as forests, shrublands and
agricultural landscapes. In addition, this study clearly showed the
ecological differences between soil fungi and bacteria on the aspect of
bipartite networks, although they had been known having the different pH
niches (Rousk et al. 2010; Peay et al. 2016) and
dependence on plants (Yang et al. 2019; Ni et al. 2021).
Conclusion
Along an broad gradient of environmental variables and plant species
richness, number of fungal OTUs specifically linked to each plant
species was positively related to plant species richness, while bacteria
showed the opposite trend. We suggest that in a more extreme high-stress
environment that decreases plant diversity, plants and fungi have fewer
excess resources to invest in specific relationships, showing up as
lower associated microbiome diversity, but that bacteria may partially
replace this role of fungi in high stress/low productivity environments.
This appears to be the first instance in which an analysis of this type,
finding plant-host links at the whole community level, has been carried
out. It would be interesting to conduct similar studies in other
ecosystems around the world.