Impact of extreme hydrological events on soil microbiome dynamics and ecosystem resilience

Anthropogenic climate change is driving a fundamental destabilization of global climate systems, transitioning historical norms toward a regime characterized by extreme hydrological events, including prolonged droughts and severe flooding. These acute “pulse” disturbances exert severe physiological shocks on the soil microbiome, a critical biological engine responsible for global biogeochemical cycling, greenhouse gas dynamics, and macroscopic ecosystem resilience. Severe drought dismantles microbial communities through intense osmotic stress and restricted substrate diffusion, leading to widespread cellular lysis, significantly reducing microbial biomass, and suppressing the catalytic efficiency of extracellular enzymes. Conversely, extreme flooding plunges the highly heterogeneous soil matrix into rapid anoxia, triggering predictable taxonomic successions, the accumulation of phytotoxins. Furthermore, extreme flooding and subsequent water-table fluctuations drive profound shifts in carbon preservation mechanisms, governed by the “Enzyme Latch” (during persistent anoxia) and the “Iron Gate” (driven by redox changes during subsequent drainage) hypotheses. The violent, rapid transition between these extremes drought abruptly followed by severe rainfall induces the “Birch Effect,” causing a massive, transient pulse of soil respiration that drastically reduces microbial Carbon Use Efficiency (CUE) and accelerates the depletion of ancient carbon pools. To widen ecosystem tolerance thresholds and accelerate recovery from these pulse disturbances, this review evaluates the implementation of Climate-Smart Agriculture (CSA) interventions, specifically highlighting the synergistic integration of biochar and continuous cover cropping. Rather than completely mitigating extreme physical forces, these targeted land management strategies buffer mild-to-moderate moisture extremes, provide structural refugia to preserve baseline microbial functionality, and align with global sustainability initiatives to secure more climate-resilient terrestrial ecosystems.