Table 1.
Initial litter chemical traits (±SE, n = 4) of four species.
Fig 1.
Principal component plot of 11 litter chemical traits of four litter species.
The first two principal components (PCs) accounted for 76.2% (PC1) and 21.9% (PC2) of the total variance, respectively. LG: lignin; CL: cellulose; SS: soluble sugar; PL: polyphenols; HP: hydrolyzable polyphenol; CT: condensed tannin; LG/N: lignin/N ratio; (LG+PL)/N: ratio of (lignin + polyphenol)/N; (LG+CL)/N: ratio of (lignin + cellulose)/N; MP: Mongolian pine; AS: A. scoparia; SV: S. viridis; PC: P. communis.
Fig 2.
Observed soil microbial biomass N (a), soil net N mineralization (b) and cumulative soil respiration (c) in relation to the expected values calculated from the corresponding monoculture treatments. The line indicates the 1:1 relationship along which observed and expected values are equal. Data points represent averages across treatments over time. ●: non-additive effects, ○: additive effects.
Fig 3.
Non-additive soil microbial biomass N (a), soil net N mineralization (b) and cumulative soil respiration (c) responses to litter mixtures as a function of chemical diversity (Hc) of litter mixtures. Dashed lines represent the 95% confidence interval of the regression. O: observed values; E: expected values. n.s.: not significant.
Fig 4.
Non-additive soil microbial biomass N (a and b) and net N mineralization (c and d) response to litter mixtures as a function of the first and second PC axes, respectively, that were used to describe chemical composition of litter. Dashed lines represent the 95% confidence interval of the regression. O: observed values; E: expected values. n.s.: not significant.
Table 2.
Summary of the ANOVA’s test for additive and non-additive effects of species mixing on soil microbial biomass N, soil net N mineralization and soil respiration using Type I sums of squares (SS).
Table 3.
The number and percentage of additive effects and non-additive effects of species mixing on soil microbial biomass N, soil N mineralization and soil respiration.
Table 4.
Summary of the ANOVA’s test to evaluate if richness and/or composition influence the non-additive effects of species mixing.
Fig 5.
Non-additive soil microbial biomass N responses to mixed-species litter as a function of individual species abundance of A. scoparia, S. viridis and P. communis within the litter mixtures.
Dashed lines represent the 95% confidence interval of the regression. O: observed values; E: expected values. n.s.: not significant.
Fig 6.
Non-additive soil net N mineralization responses to mixed-species litter as a function of individual species abundance of A. scoparia, S. viridis and P. communis within the litter mixtures.
Dashed lines represent the 95% confidence interval of the regression. O: observed values; E: expected values. n.s.: not significant.
Fig 7.
Non-additive soil respiration responses to mixed-species litter as a function of individual species abundance of A. scoparia, S. viridis and P. communis within litter the mixtures.
Dashed lines represent the 95% confidence interval of the regression. O: observed values; E: expected values. n.s.: not significant.