Figure legends
Figure 1 Characteristics of the six species cultivated in this study.
Figure 2 Schematic diagram of the experimental design. Each species contains five density gradients with three replicates, and a total of 15 plant pots are randomly placed to constitute a plot. D1: the lowest density treatment, with four plants per pot, equal to 25 plants per m2 as the area of the pot is 0.16 m2, and so on.
Figure 3 Frequency distributions of above- and belowground biomass allocation for the six species. (a) Shoot biomass fraction (SMF), (b) root biomass fraction (RMF), and (c) root to shoot ratio (R/S). Numbers in brackets identify the total samples. Different lowercase letters indicate significant differences (P < 0.05) among the six species based on one-way ANOVA and the least significant difference post hoc test. R/S was first log10-transformed to improve normality. For LC, root biomass contains both roots and rhizomes. CG, Chenopodium glaucum ; SV, Setaria viridis ; CS, Cleistogenes squarrosa ; SG, Stipa grandis ; LC, Leymus chinensis ; MS,Medicago sativa .
Figure 4 Changes in the biomass and biomass fractions with increasing planting density for the six species. Points and error bars denote the means and standard errors, respectively (n=3). Different lowercase letters indicate significant differences (P < 0.05) among the five gradients of planting density based on one-way ANOVA and the least significant difference post hoc test. For LC, root biomass contains both roots and rhizomes. (a-b) Chenopodium glaucum (CG), (c-d) Setaria viridis (SV), (e-f)Cleistogenes squarrosa (CS), (g-h) Stipa grandis (SG), (i-j) Leymus chinensis (LC), and (k-l) Medicago sativa(MS).
Figure 5 Allometric relationships between shoot and root biomass for the six species based on the data subset from each density treatment. Standard major axis (SMA) regression is used to derive the fitted line. The dashed line represents a 1:1 line. For LC, root biomass contains both roots and rhizomes. (a) Chenopodium glaucum (CG), (b) Setaria viridis (SV), (c) Cleistogenes squarrosa (CS), (d) Stipa grandis (SG), (e) Leymus chinensis (LC), and (f)Medicago sativa (MS).
Figure 6 Frequency distributions of the ANPP, and BNPP fraction, and BNPP/ANPP ratio between different functional groups using online databases and literature-reviewed data. (a) ANPP fraction for annual vs perennial; (b) BNPP fraction for annual vsperennial; (c) BNPP/ANPP ratio for annual vs perennial; (d) ANPP fraction for C3 vs C4; (e) BNPP fraction for C3 vs C4; (f) BNPP/ANPP ratio for C3 vs C4. Numbers identify the total samples. The statistical test between the two groups is based on a linear mixed effects model (generated using the ‘lmer’ function in R) with sites as the random effect. BNPP/TNPP ratios were first log10-transformed to improve normality. ***,P < 0.001.
Figure 1