The known and the unknown in soil microbial ecology.

The methodical developments in the fields of molecular biology and analytical chemistry significantly increased the level of detail that we achieve when exploring soils and their microbial inhabitants. High-resolution description of microbial communities, detection of taxa with minor abundances, screening of gene expression or the detailed characterization of metabolomes are nowadays technically feasible. Despite all of this, our understanding of soil is limited in many ways. The imperfect tools to describe microbial communities and limited possibilities to assign traits to community members make it difficult to link microbes to functions. Also the analysis of processes exemplified by enzyme activity measurements is still imperfect. In the future, it is important to look at soil at a finer detail to obtain a better picture on the properties of individual microbes, their in situ interactions, metabolic rates and activity at a scale relevant to individual microbes. Scaling up is needed as well to get answers at ecosystem or biome levels and to enable global modelling. The recent development of novel tools including metabolomics, identification of genomes in metagenomics sequencing datasets or collection of trait data have the potential to bring soil ecology further. It will, however, always remain a highly demanding scientific discipline.