Figure Legends
Figure 1 Global distribution of grassland study sites used in
the meta-analysis. Red circles and blue triangles indicate study sites
in the field and greenhouse experiments. Source data are provided as a
Source Data file.
Figure 2 Comparison of carbon and nitrogen attributes between
plant mixtures and monocultures in grasslands. The effects represent the
increase or decrease (%) of a given attribute compared to the
corresponding mean of monocultures at the mean plant diversity in
mixtures (see Methods). Values are mean ± 95% confidence intervals of
the percentage effects between the plant mixtures and monocultures. The
number of observations for each attribute is displayed in parentheses.
Abbreviations: AGB, aboveground biomass; BGB, belowground biomass; TB,
total biomass; SCP, soil carbon pool; Rs, soil respiration; Rh,
heterotrophic respiration; MB, microbial biomass; FB, fungal biomass;
BB, bacterial biomass; ANP, aboveground nitrogen pool; SNP, soil
nitrogen pool; SAN, soil ammonium nitrogen; SNN, soil nitrate nitrogen;
SNM, soil nitrogen mineralization; SNL, soil nitrogen leaching.
Different colors represent different experimental types.
Figure 3 Relationships between experimental age and the
response ratios (RR) for carbon and nitrogen attributes in the field
experiments. Plots show aboveground biomass (a), belowground biomass
(b), total biomass (c), soil carbon pool (d), soil respiration (e),
heterotrophic respiration (f), microbial biomass (g), fungal biomass
(h), bacterial biomass (i), aboveground nitrogen pool (j), soil nitrogen
pool (k), soil ammonium nitrogen (l), soil nitrate nitrogen (m), and
soil nitrogen mineralization (n). The size of the bubble is the relative
weight of the response ratio (lnRR ) in the random-effects
meta-regression. Larger bubbles indicate study outcomes that contributed
a greater overall weight in random-effects meta-regression. Solid lines
represent significant relationships. Shaded areas show 95% confidence
intervals.
Figure 4 Interactions between species richness in plant
mixtures and experimental duration in field experiments. Plots show
aboveground biomass (a), belowground biomass (b), total biomass (c),
soil carbon pool (d), soil respiration (e), heterotrophic respiration
(f), microbial biomass (g), fungal biomass (h), bacterial biomass (i),
aboveground nitrogen pool (j), soil nitrogen pool (k), soil ammonium
nitrogen (l), soil nitrate nitrogen (m), and soil nitrogen
mineralization (n). Blue, green, and red lines indicate experimental
durations of 1 year, 4 years, and mean experimental duration across all
observations; points with different shapes indicate experimental
durations. The size of the bubble is the relative weight of the response
ratio (lnRR ) in the random-effects meta-regression. Larger
bubbles indicate study outcomes that contributed a greater overall
weight in the random-effects meta-regression. Shaded areas show 95%
confidence interval of the fit.
Figure 5 Relationships between species richness and the
response ratios (RR) in the greenhouse experiments. Plots show the
aboveground biomass (a), belowground biomass (b), total biomass (c),
soil carbon pool (d), soil respiration (e), heterotrophic respiration
(f), microbial biomass (g), fungal biomass (h), bacterial biomass (i),
aboveground nitrogen pool (j), soil nitrogen pool (k), soil ammonium
nitrogen (l), soil nitrate nitrogen (m), and soil nitrogen
mineralization (n). The size of the bubble is the relative weight of the
response ratio (lnRR ) in the random-effects meta-regression.
Larger bubbles indicate study outcomes that contributed a greater
overall weight in random-effects meta-regression. Solid lines represent
significant relationships. Shaded areas show 95% confidence interval of
the fit.
Figure 6 Interactions between species richness in plant
mixtures and climate in the field experiments
(β5 ). Values are mean ± 95% confidence
intervals. Plots show mean annual temperature (a) and precipitation (b).
Abbreviations: AGB, aboveground biomass; BGB, belowground biomass; TB,
total biomass; SCP, soil carbon pool; Rs, soil respiration; Rh,
heterotrophic respiration; MB, microbial biomass; FB, fungal biomass;
BB, bacterial biomass; ANP, aboveground nitrogen pool; SNP, soil
nitrogen pool; SAN, soil ammonium nitrogen; SNN, soil nitrate nitrogen;
SNM, soil nitrogen mineralization. Data for TB comes from only one study
site thus the interactive effects of species richness and climate cannot
be tested.
Figure 7 Predicted responses of soil carbon (a) and nitrogen
(b) pools to a range of plant species richness reduction in grasslands
through field experiments. Plots show the plant species richness
reduction at 10%, 20%, 40%, and 80%. Lines with different colors
represent different species richness levels.