Arbuscular mycorrhiza helps soil functions under drought
Results from a new study from our lab shows that benefits of the AM symbiosis are not limited to plants, but also benefit soil multifunctionality
It’s quite well established that arbuscular mycorrhiza (AM), the widespread symbiosis between the roots of many plants and fungi in the Glomeromycota, helps plants cope with a range of stressful environmental conditions, including drought. Actually one of the better studied environmental stress factors in this context is drought. Much of this work has been focused on the plants, for obvious reasons, and AM fungi provide clear benefits to plant hosts under drought conditions; but are there also benefits for soil functions?
This is what a recent study from our lab asked, jointly headed by Drs. Bo Tang and Jing Man (both funded by our departmental Rising Star postdoctoral fellowship), along with Dr. Anika Lehmann. The paper is out in Global Change Biology and reports on a meta-analysis and a quite ambitious greenhouse experiment.
The meta-analysis finds that, overall, in the presence of AM, soils maintain higher functionality when exposed to drought. The sample sizes for individual soil process (like soil aggregation, different enzymatic activities) were not very high, since evidently this is not measured as often as one would think. But for the overall effect size, there were over 100 studies for AM presence and absence.
The greenhouse experiment used an ingrowth-core design (rotated vs. static cores, where rotation severs the AM-fungal hyphae; see picture below) and also featured three different plant species with different traits. The pattern was quite robust to plant species, and clearly showed that AM fungi can help maintain soil functions (multifunctionality) under drought. The pattern was also robust to watering frequency (high and low), another parameter in the experiment. Of course there still were drought-induced negative impacts on soil functions, but these were attenuated with AM fungi.
Picture showing the ingrowth core design. Each pot is equipped with two cores, one is rotated periodically (this is the non-AM fungi soil, since hyphal connection are always cut off by every rotation) and one is kept static (this is the soil in which AM fungi can grow).
The results point to an important role of the AM fungal symbiosis under drought conditions, and droughts are going to become more prevalent under climate change in many regions of the world.
Given how large the literature on AM fungi and drought effects on plants generally is, I was a bit surprised by how little data were available for several soil functions in the meta-analysis; for some functions it was in the single digits, like for microbial abundance or activity. Perhaps this is a sign that we should shift our attention a bit more to the soil when we study AM fungal networks…
Very interested studies