Plant–Microbiome Interactions for Environmental Resilience: Rhizosphere Ecology, Climate Adaptation and Ecosystem Sustainability

Droughts, heatwaves, floods and salinisation are becoming more frequent and more intense, and their consequences for crops and natural vegetation are increasingly understood to depend on the microorganisms that live on and within roots. Research on the rhizosphere microbiome has expanded rapidly, yet the literature remains fragmented across extreme types, experimental systems and disciplinary traditions, and it frequently conflates compositional change with functional benefit. This critical narrative review examines how climate extremes alter the assembly of root-associated microbial communities, which mechanisms plausibly link these changes to plant stress adaptation, and under what conditions microbial responses contribute to the resilience of plants, soils and ecosystems. Peer-reviewed literature was identified through structured searches of biomedical, life-science and multidisciplinary scholarly indexes, supplemented by backward and forward citation tracking, and was appraised for experimental design, ecological realism, causal inference and replication. The synthesis indicates that drought produces the most consistent and best-replicated signal, namely the enrichment of monoderm bacteria, particularly Actinobacteria, in root compartments across many grass and non-grass hosts, whereas the responses to heat, flooding and compound extremes are less consistently characterised and rest on fewer, often greenhouse-based studies. Mechanistic evidence is strongest for individual microbial functions, such as the degradation of the ethylene precursor 1-aminocyclopropane-1-carboxylate, iron-related processes and mycorrhizal water transport, but evidence that whole communities are actively recruited to protect the host remains largely correlative. Soil microbial legacies of past drought can modify later plant responses, although these benefits are contingent on host species, soil history and the timing of stress. Translational approaches, including inoculants, synthetic communities and host-mediated selection, show consistent benefits in controlled settings but variable establishment and performance in the field. Major unresolved questions concern causality at the community scale, the durability of legacy effects, the realism of imposed extremes, the geographical concentration of evidence and the scarcity of multi-season field trials. A predictive understanding of microbially mediated resilience will require experiments that combine realistic extreme regimes, quantitative microbial measurements and host-phenotype outcomes across contrasting soils and climates.