Hemp field retting is a bioprocess in which the stem cell wall polysaccharide network is degraded by a complex microbial consortium to facilitate further extraction of fibres. This process is carried out by farmers in an empirical way and depends on pedoclimatic conditions, which makes it difficult to control. This work aims to unravel the biodiversity-ecosystem function relationship. Retting is examined by exploring the temporal dynamics of the microbial communities considering 4 ecological indicators (density, diversity, structure, and activity). DNA metabarcoding approach and enzymatic activity are performed. The stem and extracted fiber color, the fiber biochemical composition, and the stem microstructure are evaluated. Results show that the first 2 weeks of retting are characterized by intense microbial colonization and significant biochemical changes in the composition of the fiber cell wall. This study provides the first thorough description of the hemp field retting microbiome.