Decoupling of uptake and transport-related traits in absorptive roots across coexisting herbaceous species in alpine meadows

The anatomical structure of roots determines their function. Coexisting
species complementarily forage nutrients by roots themselves (e.g., root
strategy) and their fungal partners (e.g., mycorrhizal strategy), leading
to a tradeoff between root strategy and mycorrhizal strategy. However, few
studies have specifically evaluated whether and how the root anatomical
structures are involved in this tradeoff, especially for species in alpine
ecosystems limited by extreme climate.Here, absorptive root anatomical and
chemical traits and three key root traits commonly associated with
nutrient foraging strategies, i.e., root strategy indicated by first-order
root length and root branching intensity and mycorrhizal strategy
indicated by arbuscular mycorrhizal fungal colonization, were examined
across 68 herbaceous species in alpine meadows of the Tibetan Plateau.We
observed that absorptive roots with higher branching intensity had more
protoxylem poles, thinner cortices and smaller cortical cells, whereas
absorptive roots with higher mycorrhizal colonization and longer
first-order roots consistently had thicker cortices and larger cortical
cells. Unexpectedly, root cortical traits responsible for nutrient uptake
were decoupled from stelar traits specialized in water and nutrient
transportation. The decoupling may be related to the non-coordinated
changes in soil water and nutrient availability in the meadows of the
Tibetan Plateau. In addition, we found that root cortical thickness and
stelar radius increased at a similar rate rather than well-reported
different rates with increasing root diameter. Our results
demonstrate that root internal makeup plays an integral role in forming
the diverse nutrient foraging strategies in belowground. These findings
provide new insights into our understanding of plant coexistence and
responses of alpine meadows to climate change on the Tibetan Plateau.