FIGURE CAPTIONS
FIGURE 1 Conceptual model of the role of ECM symbionts in plant N and P uptake
FIGURE 2 Schematic diagram of variation partitioning in determining the effects of soil variables, climate factors, and ECM traits on root and foliar nutrient variables. Values in diagram represents the explained variations in each category of factors and various interactions.
FIGURE 3 Analysis of structural equation models (SEMs) on root and foliar nutrient variables. *, P < 0.1; **, P<0.05; ***, P<0.01. Standardized path coefficients (δ) were showed on line arrows. R2 value represents the proportion of total variance explained for the specific dependent variable. (a1): SEMs depicting the regulatory pathway of the controls in root P; (a2): SEMs depicting the regulatory pathway of the controls in root N; (a3): SEMs depicting the regulatory pathway of the controls in root N:P; (b1): SEMs depicting the regulatory pathway of the controls in leaf P; (b2): SEMs depicting the regulatory pathway of the controls in leaf N; (b3): SEMs depicting the regulatory pathway of the controls in leaf N:P. ECM-PC1: the first principal components of ECM traits by PCA; ECM-PC2: the second principal components of ECM traits by PCA. MAT: the mean annual temperature; MAP: the mean annual precipitation. Soi-PC1: the first principal components of soil factors principal component analysis (PCA); Soi-PC2: the second principal components of soil factors by PCA.
FIGURE 4 Redundancy analysis (RDA) ordination biplot of ECM traits and root nutrients (a) and foliar nutrients (b). Cratio: Colonization ratio of ECM fungi; CE: ECM roots with contact exploration type; ECMtips: ECM root tips per unit root biomass; FRB: Fine root biomass; MDE: ECM roots with medium exploration type; MDI: Morphology diversity index; Root-tipsratio: the ratio of the living to dead root tips; SA: superficial area of ECM; SDE: ECM roots with short distance exploration type; MiNR1: sampling at 3077 m asl . in Miyaluo Nature Reserve; MiNR2: sampling at 3612 m asl . in Miyaluo Nature Reserve; WaNR1: sampling at 3070 m asl . in Wanglang Nature Reserve; WaNR2: sampling at 3150 m asl . in Wanglang Nature Reserve; WoNR1: sampling at 2850 m asl . in Wolong Nature Reserve; WoNR2: sampling at 3000 m asl . in Wolong Nature Reserve; WoNR3: sampling at 3194 m asl . in Wolong Nature Reserve; WoNR4: sampling at 3413 m asl . in Wolong Nature Reserve; WoNR5: sampling at 3593 m asl . in Wolong Nature Reserve.
FIGURE 5 The significant relationships of root and foliar nutrients with soil exploration types. (a): the regressions of root P and the colonization ratio of CE; (b): the regressions of root P and the colonization ratio of SDE; (c): the regressions of root N and the colonization ratio of SDE; (d): the regressions of sqrt(root P) and sqrt(the colonization ratio of MDE); (e): the regressions of root N:P and the colonization ratio of MDE; (f): the regressions of foliar N:P and the colonization ratio of MDE. CE: ECM roots with contact exploration type; SDE: ECM roots with short-distance; MDE: ECM roots with medium exploration type.
FIGURE 6 A conceptual model of the intervention of ECM symbiosis on root and foliar N and P nutrients in A. faxoniana . I: The primary effects of ECM symbiosis on root nutrients. Root N and P nutrients could both be strongly affected by ECM symbiosis, but the effects were stronger on root P than root N; II: Indirect mediation of ECM symbiosis on foliar N and P nutrients driven by the nutrient limitation signals from leaves to roots; III: Changes in foliar N and P nutrients caused by variations in ECM strategies. Changes in ECM foraging strategies imposed greater influences on foliar P than foliar