Coordination of leaf and root economic space in alpine coniferous forests on the Tibetan Plateau

Coordination between leaf and root traits is crucial to plant performance and ecosystem functioning, but how leaves and roots coordinate in ectomycorrhizal (ECM)-dominated alpine forests remains unclear. Therefore, the covariation patterns of leaf and root traits of ECM-dominated alpine conifers and the environmental drivers were examined. Five pairs of key leaf (i.e., leaf thickness [LT], specific leaf area [SLA], leaf tissue density [LTD], leaf N and P concentrations) and fine-root traits (i.e., root diameter [RD], specific root length [SRL], root tissue density [RTD], root N and P concentrations) were measured across 49 alpine coniferous populations (including 8 coniferous species) on the Tibetan Plateau. Root traits including RTD, root N and P concentrations and leaf traits such as LT, SLA, LTD, leaf N and P concentrations were correlated. The root-leaf relationships represent a tradeoff between resource conservation and fast plant growth, i.e., plant economic spectrum. RD and SRL were independent from the plant economic spectrum. Temperature drove variations in the leaf traits, RTD, root N and P concentrations, and conifers under low temperature had denser leaves and roots (i.e., larger LT, LTD, RTD) and lower nutrient contents. Precipitation primarily controlled variations in RD and SRL, and roots became thinner with decreasing precipitation. Our study demonstrates divergent roles of temperature and precipitation in driving the coordination of leaf and root economic traits in the ECM-dominated alpine coniferous ecosystems. This is insightful for a comprehensive understanding of the adaptation and responses of alpine forests to climate change.