Precipitation, rather than temperature drives coordination of multidimensional root traits with ectomycorrhizal fungi in alpine coniferous forests

The interactions between roots and mycorrhizal fungi are critical for our
understanding of the multidimensional root economics space. Our knowledge
on their relationships comes mainly from arbuscular mycorrhizal (AM)
plants, and less is known about how roots are coordinated with
ectomycorrhizal (ECM) fungal communities, especially in ECM-dominated
alpine forests that are highly sensitive to climate change worldwide.
Here, we investigated the coordination between roots and ECM fungi and
their drivers by measuring multiple root traits, ECM fungal composition
and environmental factors of 47 coniferous populations across the alpine
coniferous forests on the Tibetan Plateau. Our results reveal two
independent fine-root trait dimensions, i.e., root foraging dimension and
root uptake dimension, which are represented by root diameter-specific
root length, root tissue density-root N concentration. Importantly, the
hyphal exploration-type-based ECM foraging correlated significantly with
both root foraging and root uptake dimension. Further, in the
low-temperature plateau, it is precipitation-induced changes in soil
moisture, soil nutrients and pH that drive the proportion of
longer-distance hyphal exploration types to increase with higher root
foraging by higher specific root length, and to decrease with higher
uptake by higher root N concentration. Synthesis. The coordination of
multidimensional root traits with ECM fungi differs greatly from the
well-recognized pattern in AM plants that mycorrhizal fungi connect
predominantly with root foraging and that roots and mycorrhizal fungi are
temperature sensitive. These findings provide a new insight for our
holistic understanding of how roots and mycorrhizal fungi vary
collaboratively and hence driving plant community assembly and responses
to the changing climate.