Multiple stressors and limits to inoculation as part of restoration approaches
Multiple stressors, community coalescence, and climate change (global change) mitigation
In a recent paper in Science, Allsup et al. (2023), also see the nice comment in Science by Michelle Afkhami, presented research on tree survival when these trees were inoculated with microbial communities stemming from soils that have experienced certain climate-change relevant stress factors, such as drought or cold. So, trees had a higher probability of survival when experiencing unusual cold when they were inoculated with microbes from soils that had experienced cold conditions. The remarkable aspect of this work is that it took place over 3 years in the field, it worked across different tree species, and also (at least in part) different mycorrhizal types, and the microbial communities still remained different after this time.
In her commentary, Michelle Afkhami highlights one aspect that also caught my eye: this did not work well when there was more than one stressor. So when there was not just winter cold, but also summer drought (done by rainout shelters in the field), this inoculation scheme did not help. Now, as I have written in previous newsletters, being exposed to multiple stressors is the rule rather than the exception, with these simultaneous multiple stressor impacts leaving a signature on soils and ecosystems. We showed this most recently also in a global observational study (Rillig et al. 2023, Nature Climate Change). So this raises the question: can we somehow use soil microbiomes to make plants multiple-stressor ready? Could this work and how would one go about this?
The other point, always an issue in any inoculation approach with a complex inoculum (such as in the present study), is that the inoculated community then will interact with an existing community. We described this phenomenon as microbial community coalescence (see also a previous newsletter). This is important to realize, in part because it makes everything more complicated, but also interesting. It is quite possible that the function arising from the inoculation stems from an interaction between the two communities that have undergone this community coalescence event; the resident community (in this case the community at the field site) and the inoculated community (in this case the one that came with the tree).
So, can this kind of inoculation approach work to help mitigate the effects of anthropogenic impacts: I think yes, but we really need to understand better what causes this pattern of improved plant performance. And this includes understanding the multi-stressor impacts - and testing if this can work in inoculation approaches - and also the resulting community coalescence dynamics. Both are hard, but I believe this can be done.
What do you think?