Changes in Microbial Carbon and Nitrogen Cycling in Wetlands Under Moisture Stress

Abstract The increasing frequency of drought events, driven by climate change and anthropogenic activities, has significantly challenged wetland ecological conservation, exacerbating nutrient limitations for both plant and microbial communities within these ecosystems. However, the adverse effects of drought stress on marsh wetland health, particularly the microbial‐driven mechanisms underlying wetland material cycling, are not yet fully understood. To address this issue, a 6‐year controlled hydrological experiment was conducted in selected wetlands in north‐east China. Changes in wetland ecological functions were studied through long‐term automatic control of four different water levels: L1 (severe drought), L2 (mild drought), L3 (control), and L4 (inundation). The results showed that severe drought and inundation reduced soil nitrogen availability (mainly NH 4 + , −34.4%–43.6%). Microbial communities exhibited adaptive responses to water and nutrient deficiencies through metabolic regulation, particularly by suppressing energy production pathways, including glycolysis/gluconeogenesis and the tricarboxylic acid cycle. In terms of material cycling, drought significantly promotes microbial nitrogen fixation (+31.7%–419.4%), providing important potential conditions for mitigating nitrogen limitation in wetlands. Regarding ecological functions, inundation conditions were found to promote wetland microbial methanogenesis, whereas drought conditions favored microbial N 2 O production processes. Seasonal variations were also identified in environmental factors influencing carbon and nitrogen metabolic pathways. The results of our study provide theoretical support for future wetland ecological conservation, particularly for mitigating nutrient depletion in ecosystems under extreme climate change.