Work

Beyond taxonomic richness: Network topology and functional gene abundance reveal tillage and nitrogen as physiological and topological filters across heterogeneous corn agroecosystems

Year: 2026

Type: article

Abstract: Soil microbial communities underpin key ecosystem functions, yet their responses to agricultural intensification remain difficult to predict across heterogeneous landscapes. This study evaluated the impact of nitrogen (N) fertilization rates (0-200 kg N/ha) and tillage intensity (Conventional Ploughing, Reduced Tillage, Direct Drilling) on bacterial diversity, functional potential, and co-occurrence networks across 84 corn fields in southern Québec, Canada. Using 16S rRNA gene sequencing and qPCR of N-cycling genes (nifH, amoA, nirK), we reveal a hierarchy of drivers. Soil texture and pH dominated bacterial composition, explaining ~46% of the variance and overwhelming the effects of management on alpha- and beta-diversity. Texture also constrained topology, with fine soils favoring dense, centralized networks while coarse soils promoted decentralized, modular architectures. However, this taxonomic homeostasis concealed a reorganization of function and structure. Nitrogen fertilization induced a functional reallocation, significantly increasing amoA and suppressing nifH gene abundance. Furthermore, tillage intensity reshaped microbial network topology, with Direct Drilling promoting modular and niche-partitioned networks, while Reduced Tillage exhibited low connectivity and high centralization, suggesting a structural vulnerability in transitional systems. These patterns indicate that agricultural management operates primarily as a physiological and topological filter rather than a taxonomic driver, consistent with concepts of functional redundancy and network-mediated stability in microbial ecosystems. Thus, soil health assessments should move beyond taxonomic richness to include indicators of network topology and functional gene abundance, which offer more sensitive metrics of ecosystem resilience. Consequently, sustainable management strategies must prioritize preserving these microbial interaction architectures and functional redundancy to ensure long-term soil fertility.

Source: Applied Soil Ecology

DOI: 10.1016/j.apsoil.2026.107498

Authors: Josselin Bontemps, Thiago Gumiere, Gabriel Deslauriers, Richard Hogue, Jacynthe Dessureault-Rompré

Institutions: Université Laval, Institut de Recherche et de Développement en Agroenvironnement

Language: English

Topic: Soil Carbon and Nitrogen Dynamics

Subfield: Soil Science

Field: Agricultural and Biological Sciences

Domain: Life Sciences

SDGs: Life on land, Zero hunger

Open Access status: hybrid

Estimated APC paid: $4,320