Meta-analysis of ecological and phylogenetic biomass maturity metrics

Although a wide variety of biomass sources have been subjected to 16S rRNA gene sequencing, ecological and phylogenetic signatures of maturity have not been identified quantitatively. In this meta-analysis we reanalyzed data from the only published study with publicly available 16S and temperature data (Zhou et al., 2018), and then applied the Zhou results to 705 samples from 13 additional studies. Using the Zhou data, we found that Faith's alpha diversity index correlated inversely with compost temperature and positively with maturity. We also noted a dramatic shift in the ratios of Bacilliota to Acidobacteriota, Planctomycetota, and Pseudomonadota, as samples cooled below 44 °C (p < 0.001). A negative correlation between Bacillota and Pseudomonadota was also observed in all 705 samples that included compost, sugarcane mill mud, anerobic digestates, and vermicompost. Even in the absence of temperature data for the majority of samples, our meta-analysis shows that microbiomes of diverse residuals converged on similar communities that resemble those of soil, regardless of the starting material or residual management process. We propose that approximately < 0.4 log(Bacillota:Pseudomonadota) and > 43 Faith's phylogenetic diversity indices are indicative of maturity of diverse biomass materials destined for land application.