Figure 2.

Relationship between plant diversity and productivity (in grams) in four experimental soil types. Sterile (squares), sterilized field soil; Sterile + AMF (diamonds), sterilized field soil + field-collected AMF spores; Sterile + pathogens/parasites/saprobes (circles), sterilized field soil + microbial fraction that excludes AMF (<20 microns); and Field Soil (triangles), untreated field soil. Productivity varied significantly with diversity (ANOVA F_3,64 = 523.2; p = 0.0001), soil treatment (F3,64 = 66.7; p = 0.0001), and the interaction (F_9,64 = 12.4; p = 0.0001). Lines represent the best fit with linear and polynomial functions (AIC_sterile = 0.04; AIC_{sterile + AMF} = 2.97; AIC_{sterile + pathogens} = 9.86; AIC_field soil = 9.91). Error bars represent ±1 SE. Figure reprinted from Schnitzer et al.¹