Nutrient trade‐offs mediated by ectomycorrhizal strategies in plants: Evidence from an Abies species in subalpine forests

1.Ectomycorrhizal (ECM) roots are evolutionary strategies of plants for effective nutrient uptake under varying abiotic conditions. Formation and morphological differentiations of ECM roots are important strategies in foraging environments. However, little is known on how such strategies mediate the nutrients of the below- and aboveground tissues and the balances among nutrient elements across environmental gradients. 2.We studied the function of ECM symbiosis in Abies faxoniana across its distributional range in Southwest China. The effects of differential ECM strategies, i.e. the contact exploration type, the short-distance exploration type, and the medium-distance exploration type, and root tips functional traits, etc., on root and foliar N and P and N:P ratio were examined across natural environmental gradients. 3.The ECM symbionts preferentially facilitated P uptake in A. faxoniana under both N and P limitations. The uptakes of N and P were primarily promoted by the effectiveness of ECM roots, e.g. ECM root tips per unit biomass, superficial area of ECM root tips, the ratio of living and dead root tips, but negatively related to the ECM proliferations and morphological differentiations. Generally, plant N and P nutrients were always promoted by the contact exploration type, while negatively affected by the short-distance exploration type in A. faxoniana. Root and foliar N and P nutrients were expected to be affected by the medium-distance exploration type in dynamics. Especially, root P limitation could be relieved when the frequency of medium-distance exploration type up to c.15%, whilst root N limitation was strengthen when the frequency of medium-distance exploration type over 20%. 4.We suggest that both below- and above-ground nutritional traits of host tree species could be strongly affected by ECM symbiosis in natural environments. The ECM strategies responding to environmental conditions significantly affect the plant nutrient uptakes and trade-offs. ECM soil exploration types are the great supplementary mechanisms for plant nutrient uptake.