The importance of plant traits in diversity-productivity
relationships
Our results confirm that functional traits of tree communities have an
important effect on fungal community composition (Yang et al.2020; Prada-Salcedo et al. 2021). The tree functional identity
axis represents a gradient in tree communities with more acquisitive
traits, higher Nmass and Amax (positive FI) to more conservative traits,
higher LL and LMA (negative FI). Therefore, the direct negative effect
of functional identity on productivity suggests that communities with
more conservative traits have higher community productivity. Fungal
community composition mediated a positive, indirect effect of tree
functional identity on productivity, in contrast to the observed
negative, direct effect of tree functional identity on productivity.
Therefore, tree communities with more conservative traits alter fungal
communities in a way which lowers productivity and fungal communities
counteract the direct effect of tree functional traits on productivity.
Pathogen richness was also negatively associated with functional
identity, indicating that acquisitive plant traits, such as higher Nmass
and Amax, are associated with lower pathogen richness, contrary to the
results of previous studies (Blumenthal et al. 2009; Parker &
Gilbert 2018). Pathogen and ECM richness interactively mediated an
indirect effect of functional identity on productivity. Functional
identity was also an important driver of NE and CE, but only through
positive, indirect effects of fungal community composition. Therefore,
variation in plant traits among tree communities interact with fungal
communities to promote productivity of mixed tree communities.