Multiple dimensions of phylogenetic diversity are needed to explain the complex aboveground-belowground diversity relationships

The complex relationship between aboveground and belowground diversity and
whether they act as surrogates for one another remains unresolved.
Increasing evidence suggests that investigating phylogenetic diversity
could provide valuable insights into the interplay between plants and soil
microbes, but the proliferation of phylogenetic diversity metrics has
hindered comparative studies and the identification of general patterns.
To overcome this challenge, we implemented a multi-dimensional framework
that classifies phylogenetic diversity metrics into three dimensions:
richness, divergence, and regularity, each of which captures different
ecological aspects of species differences. Then we applied this framework
to investigate the relationship between above and belowground diversity in
a subtropical forest in Eastern China. We found that phylogenetic
diversity of plant and soil microbes, including bacteria and fungi, were
more strongly correlated at the richness and regularity dimension compared
with divergence dimension. Further analyses revealed that these observed
correlation patterns can be attributed to the influence of soil total
phosphorus content, which is the limiting factor of plant and microbial
phylogenetic diversity at richness and regularity dimensions. Together,
our study demonstrated the necessity of using a multi-dimensional approach
to advance our understanding of the complex relationships between plant
and soil microbial biodiversity.