Conclusion
In our study, we sought to determine whether the widespread keystone
grass, Themada triandra , relied on soil microbiota from arid
locations to gain growth advantages when grown under drought conditions.
We report that soil microbiota from more arid sources had strong
positive effects on plant growth under drought conditions. We also show
that soil aridity, water stress, and sterilisation treatments shaped
both plant growth and the soil-to-endosphere recruitment as described by
the two-step selection process. Finally, soil physicochemical variables
associated with our stress and sterilisation conditions influenced the
composition of bacterial communities far more strongly that the presence
of T. triandra plants. Together, these results highlight that
grassland decline by increased aridity due to climate change may be in
part mitigated by the effects of healthy soil microbiota on keystone
grass species. As such, we anticipate that soil-based manipulations to
enhance the restoration of climate-resilient grasslands will be
increasingly applicable to future interventions in grassland
ecosystems.