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