Continuous maize cropping is often associated with yield decline and soil degradation, yet the temporal responses of rhizosphere bacterial communities to prolonged monocropping remain incompletely understood. Here, we used a continuous maize cropping chronosequence representing 0, 1, 2, 3, 6, 7, and 8 years of cropping to evaluate soil physicochemical properties, maize yield, rhizosphere bacterial community composition, and BugBase-predicted phenotypes using 16S rRNA gene amplicon sequencing. Available potassium declined progressively with cropping duration, whereas alkali-hydrolyzable nitrogen (AN) increased and available phosphorus (AP) changed nonlinearly. Soil pH declined in the later stages of the chronosequence. Maize yield declined progressively with prolonged cropping, with reduction of 46–55% in the 6–8 years treatments relative to earlier within-plot peaks. Bacterial alpha diversity changed nonlinearly, with Shannon diversity peaking at C3, declining at C6, and partially recovering at C7–C8. Because years 4 and 5 were not sampled, the exact shape of the transition between C3 and C6 remains unknown. Community composition also shifted with cropping duration, including a relative decline in Proteobacteria and enrichment of Actinobacteria in the longer-duration treatments. At the genus level, Arthrobacter increased in the later stages of the chronosequence. Redundancy analysis indicated broad associations between community composition and soil variables, although the phylum-level model was only marginally significant. BugBase-predicted phenotypes also varied across treatments, but these functional inferences should be interpreted cautiously because they were derived from 16S-based predictions. Overall, our findings support nonlinear changes in rhizosphere bacterial communities along the continuous maize cropping chronosequence and suggest an unresolved transition between C3 and C6, followed by partial stabilization at later stages. However, due to the missing data for years 4–5 and the inherent limitations of the chronosequence design, the existence and timing of a proposed mid-term transition remain tentative. These findings highlight the need for complete annual sampling to resolve successional trajectories.

This study investigated how fertilization regimes and ridge furrow planting patterns influence the soil nutrient conditions and microbial taxonomic composition and function in the rhizosphere of spring maize in Northeast China. Three treatments were compared: CK (compound fertilizer, small ridge), KF (formula fertilization, small ridge), and BMP (formula fertilization, large double-row ridge). High-throughput sequencing was used to characterize the soil bacterial and fungal community composition and diversity. The results showed that the combination of formula fertilizer and wide-ridge cultivation synergistically improved soil physicochemical properties and significantly increased maize yield (p < 0.05). Compared with CK, both BMP and KF significantly improved the composition and diversity of microbial communities. Notably, the BMP treatment increased the relative abundances of Ascomycota and Basidiomycota—key decomposers of soil organic matter, lignin, and cellulose—which suggested enhanced nutrient cycling potential under this integrated management practice. Among the three treatments, BMP (N:P₂O₅:K₂O = 1:2:1, 130 cm wide-ridge double-row planting) achieved the highest maize yield (859 ± 14 kg ha⁻¹), representing an 11.0% increase over conventional practices (CK, 774 ± 13 kg ha⁻¹). We propose that integrating optimized fertilization with ridge configuration is an effective strategy for improving soil quality, microbial functionality, and crop productivity in Northeast China’s black soil region.

Moss-dominated biological soil crusts are associated with carbon and nitrogen cycling in dryland and alpine sandy ecosystems, but functional differentiation among closely related moss species and their mixed assemblages remains unclear. We used shotgun metagenomic sequencing to compare below-crust soil associated with Didymodon constrictus (Mitt.) K. Saito (D. constrictus) crusts (mossC), ferrugineus (Schimp. ex Besch.) M.O. Hill (D. ferrugineus) crusts (mossF), and visually co-dominated mixed crusts (mossM) in the Gonghe Basin on the northeastern Qinghai–Tibet Plateau. Fifteen spatially separated quadrats per category were pooled into three composite biological replicates (effective n = 3). KEGG, CAZy, and targeted carbon- and nitrogen-cycling annotations showed category-associated differences in relative gene representation. MossC had greater mean representation of glycoside hydrolases and several complex-carbon-processing functions, mossF had greater representation of nitrogen-assimilation and acetate-related functions, and mossM had greater representation of selected carbon-degradation, nitrogen-mineralization, and dissimilatory-nitrate-reduction functions. The full RDA model explained 58.4% of functional variation (adjusted R² = 0.334; exact permutation p = 0.028340), with single-variable associations retained for total carbon and soil water content. Genus-level taxonomic dissimilarity correlated with KEGG, CAZy, carbon-cycling, and nitrogen-cycling dissimilarities after FDR correction. MossM showed both positive and negative descriptive deviations from the approximate unweighted midpoint of mossC and mossF, but no inferential test was applied to these deviations. The small number of composite replicates, visually estimated moss proportions, edaphic confounding, and absence of activity measurements limit causal and confirmatory interpretation.