Cadmium (Cd) contamination in agricultural soils threatens food security and exacerbates climate change through its impact on greenhouse gas (GHG) (CO₂, N₂O and CH₄) emissions, in which N₂O and CO₂ are the dominant fluxes of the terrestrial carbon-nitrogen cycle whose magnitude is directly amplified by Cd stress. Key remediation approaches for this dual challenge are phytoremediation and biochar amendment. This study aims to investigate the effects of Solidago canadensis (CGR) and biochar (BC) on soil remediation and GHG emissions under different levels of Cd contamination. A pot experiment with four Cd concentration gradients (0, 5, 10, and 30 mg kg⁻¹, i.e., Cd-0, Cd-5, Cd-10, and Cd-30, respectively) and three remediation measures (control, BC addition, and CGR cultivation) was set up to measure available soil Cd (ACd), soil physicochemical properties, GHG emissions, and plant Cd accumulations. The results demonstrated that ACd was significantly reduced by BC via adsorption through surface complexation and by CGR via immobilization through root uptake and sequestration. CGR decreased ACd by 46.2% and 41.7% under mild and moderate Cd contamination, respectively, while BC reduced ACd by 8.9% under severe contamination. In terms of GHG emissions, CGR increased cumulative CO₂ by 83.4% in Cd-10 soil and 53.8% in Cd-30 soil, whereas BC significantly lowered N₂O emissions by 22.1% in Cd-5 soil. Mantel analysis revealed strong correlations between ACd and key carbon and nitrogen indicators, which mediate the bioavailability of Cd. Therefore, CGR cultivation is better suited to mild-to-moderate contamination given its high removal efficiency, while BC amendment is targeted at severe contamination by stabilizing Cd and mitigating N₂O. This provides a scientific basis for the remediation of Cd-contaminated soils.

Acidic soils are widespread in global agroforestry systems and severely constrain crop production through proton stress, aluminum/manganese phytotoxicity, phosphorus fixation, and rhizosphere microbiome reassembly. Rhizosphere diazotrophs can theoretically contribute to plant nitrogen (N) nutrition and stress adaptation. However, their N-fixation efficiency and growth-promoting effects in acidic soils are often highly unstable, limiting the predictability of field applications. This narrative mechanistic review synthesizes and critically interprets evidence on the physicochemical filters governing diazotroph survival in acidic soils, nitrogenase regulation, root-exudate-mediated recruitment, multi-guild microbial interactions, and the conditional design of synthetic microbial communities (SynComs) and inoculant formulations. We further discuss the potential complementary roles of phosphate-solubilizing bacteria (PSB) and arbuscular mycorrhizal fungi (AMF) and propose minimum reporting standards to improve field translatability. The synthesis indicates that effective diazotroph-mediated crop promotion depends on pH buffering, metal detoxification, carbon supply, phosphorus availability, host compatibility, and native microbiome receptivity. The proposed evidence-chain and microbiome-compatibility framework is a conceptual guide for evaluating these linked conditions rather than an empirically validated predictive model.

Amid intensifying climate change, moso bamboo (Phyllostachys edulis), a fast-growing East Asian native invasive species, has rapidly expanded in subtropical and temperate forests of southeastern China, increasing moso bamboo forest area by 85% from 1988 to 2018, primarily invading broadleaf, coniferous, or mixed forests in natural mountainous, altering forest structure while influencing soil greenhouse gas (GHG) emissions. This chapter synthesizes mechanisms by which moso bamboo’s natural expansion in non-managed forest ecosystems affects soil fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Despite its high biomass production (50–100 Mg ha−1) and potential as a carbon sink for climate mitigation, bamboo’s dense root systems, high litter inputs (1656–1928 kg ha−1 yr.−1), and low C:N ratio litter accelerate root respiration and microbial decomposition, elevating CO2 emissions (root respiration rates 1.08–7.87 μmol m−2 s−1). Concurrently, enhanced soil aeration and pH shifts promote methanotrophic bacterial activity, boosting CH4 uptake (120–180 μg m−2 h−1). Low C:N litter accelerates N mineralization, stimulating nitrification and denitrification processes, with N2O emissions modulated by forest composition and reshaped microbial communities (e.g., increased Actinobacteria and Proteobacteria abundance). Overall, bamboo expansion elevates soil organic carbon storage (20–40 Mg ha−1) but yields complex net climate impacts due to intertwined C-N cycles. Management implications include monitoring bamboo encroachment in biodiversity hotspots. Future research should prioritize long-term flux measurements and metagenomic analyses under climate scenarios to guide ecological conservation and GHG mitigation strategies.