Earthworm-Driven Changes in Soil Chemico-Physical Properties, Soil Bacterial Microbiota, Tree/Tea Litter Decomposition, and Plant Growth in a Mesocosm Experiment with Two Plant Species

Abstract

Earthworms and soil microorganisms contribute to soil health, quality, and fertility, but their importance in agricultural soils is often underestimated. This study aims at examining whether and to what extent the presence of earthworms (Eisenia sp.) affected the (a) soil bacterial community composition, (b) litter decomposition, and (c) plant growth (Brassica oleracea L., broccoli; Vicia faba L., faba bean). We performed a mesocosm experiment in which plants were grown outdoors for four months with or without earthworms. Soil bacterial community structure was evaluated by a 16S rRNA-based metabarcoding approach. Litter decomposition rates were determined by using the tea bag index (TBI) and litter bags (olive residues). Earthworm numbers almost doubled throughout the experimental period. Independently of the plant species, earthworm presence had a significant impact on the structure of soil bacterial community, in terms of enhanced α- and β-diversity (especially that of Proteobacteria, Bacteroidota, Myxococcota, and Verrucomicrobia) and increased 16S rRNA gene abundance (+89% in broccoli and +223% in faba bean). Microbial decomposition (TBI) was enhanced in the treatments with earthworms, and showed a significantly higher decomposition rate constant (kTBI) and a lower stabilization factor (STBI), whereas decomposition in the litter bags (dlitter) increased by about 6% in broccoli and 5% in faba bean. Earthworms significantly enhanced root growth (in terms of total length and fresh weight) of both plant species. Our results show the strong influence of earthworms and crop identity in shaping soil chemico-physical properties, soil bacterial community, litter decomposition and plant growth. These findings could be used for developing nature-based solutions that ensure the long-term biological sustainability of soil agro- and natural ecosystems.

Copper toxicity on Eisenia fetida in a vineyard soil: a combined study with standard tests, genotoxicity assessment and gut metagenomic analysis

“…Furthermore, Comamonadaceae are also thought to be important plant associates in the control of phytopathogens because of their enzymatic activities. Changes in the abundances of some bacterial groups in our study can also be considered as potential indicators of the ability of earthworms to alter the structure of the soil bacterial community as the abundance of Proteobacteria and Bacteroidota (of which most abundant families found in the gut microbiomes in our study also belong) were closely related to earthworm activities in the soil in a study conducted by Sofo et al ( 2023 ). These observed trends in microbial abundance, influenced by Cu exposure, reflect not only the direct impacts on specific bacterial families but also broader ecological implications.…”

Copper Toxicity on Eisenia Fetida in a Vineyard Soil: A Combined Study with Standard Tests, Genotoxicity Assessment, and Gut Metagenomic Analysis

“…Furthermore, Comamonadaceae are also thought to be important plant associates in the control of phytopathogens because of their enzymatic activities. Changes in the abundances of some bacterial groups in our study can also be considered as potential indicators of the ability of earthworms to alter the structure of the soil bacterial community as the abundance of Proteobacteria and Bacteroidota (of which most abundant families found in the gut microbiomes in our study also belong) were closely related to earthworm activities in the soil in a study conducted by Sofo et al (2023). These observed trends in microbial abundance, influenced by Cu exposure, reflect not only the direct impacts on specific bacterial families but also broader ecological implications.…”

Impact of Sea Rice Planting on Enzymatic Activity and Microbial Community of Coastal Soils: Focus on Proteinase

“…The organic fertilizers applied in farming, plant debris as well as animal feces and carcasses contained a large amount of protein [47,48]. Proteinases play a major role in nitrogen mineralization in soil, by catalyzing the hydrolysis of peptide bonds of proteins to peptides and amino acids [42].…”