The role of water availability in diversity-productivity
relationships
Soil fungi may play a role in the diversity-productivity relationship
through their impact on plant water relations
(Lehto & Zwiazek 2011). In the null
models, water availability had no significant, direct effect on
above-ground productivity, whereas in the models that included fungal
richness and community composition, water availability had a positive,
direct effect on productivity. Furthermore, fungal richness and fungal
community composition mediated negative, indirect effects of water
availability on productivity. These negative, indirect effects were
strong enough to counteract the positive, direct effects of water
availability on productivity, resulting in the apparent lack of a
significant, direct effect of water availability in the null models.
These results suggest that changes in the fungal richness and community
composition under water-limited conditions may alleviate plant water
stress and regulate productivity
(Gehring et al. 2017).
On the other hand, there was no connection between water availability
and diversity effects in the full or null models. Although water
availability directly influenced fungal community composition, NE and CE
were independent of water availability. This suggests that fungal
communities affect tree water relations similarly in monocultures and
mixed communities. Therefore, the mechanism of complementarity in this
system is likely not related to buffering of water stress in mixed
communities (Verheyen et al.2008; Belluau et al. 2021). Instead, we suggest that fungal
communities may play a role in diversity-productivity relationships and
complementarity through the interaction of pathogens and ECM, which may
be associated with biotic feedbacks and/or niche partitioning.