Data from: Mycorrhizal symbiosis pathway and edaphic fertility frame root economics space among tree species

The root economics space (RES) is multidimensional and largely shaped by
belowground biotic and abiotic influences. However, how root-fungal
symbioses and edaphic fertility drive this complexity remains unclear.
Here, we measured absorptive root traits of 112 tree species in temperate
and subtropical forests of China, including traits linked to functional
differences between arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM)
hosts. Our data, from known mycorrhizal tree species, revealed a
‘fungal-symbiosis’ dimension distinguishing AM from ECM species. This
divergence likely resulted from the contrasting mycorrhizal evolutionary
development of AM versus ECM associations. Increased root tissue cortical
space facilitates AM symbiosis, whereas increased root branching favors
ECM symbiosis. Irrespective of mycorrhizal type, a ‘root-lifespan’
dimension reflecting aspects of root construction cost and defense was
controlled by variation in specific root length and root tissue density,
which was fully independent of root nitrogen content. Within this
function-based RES, we observed a substantial covariation of axes with
soil phosphorus and nitrate levels, highlighting the role played by these
two axes in nutrient acquisition and conservation. Overall, our findings
demonstrate the importance of evolved mycorrhizal symbiosis pathway and
edaphic fertility in framing the RES, and provide theoretical and
mechanistic insights into the complexity of root economics.