Fig. 2

Relationship between microbial composition indices and soil multifunctionality. The total fungal and bacterial OTU richness are shown in relation to a multifunctionality, b the average number of taxa that support a function, where larger values indicate that on average there are more taxa that support the same function, and c functional uniqueness where larger values indicate a greater dissimilarity among taxa in the functions they support. d Proportion of the microbial community needed to support a given combination of functions, from single functions to all 10 functions, illustrating that more taxa are needed to support multiple functions as more functions are considered²⁵. Dashed regression lines show combinations of functions (in orange) that exclude P uptake by legumes and forbs and N uptake by legumes for fungi and N₂O emissions for bacteria. These cluster out because these functions had a relatively high number of taxa that supported them (Table S5). Thus, there is a smaller proportion of the community that supports individual functions when these are excluded. Ecosystem multifunctionality was positively related to (e) the average number of taxa that support a function and (f) functional uniqueness. For a–c both fungi and bacterial richness was combined by taking their scaled (between 0 and 1) average richness. Significance is indicated by *P < 0.05, **P < 0.01, ***P < 0.001 for each linear regression