Seminar:Jarin Jose

Soil microbial growth, respiration, and carbon use efficiency (CUE) are fundamental regulators of soil organic carbon (SOC) cycling, as they govern microbial biomass formation and later necromass in soil. However, the specific environmental and microbial determinants shaping these traits remain insufficiently understood. In this study, we investigated soils from grassland and forest ecosystems across three regions within the Biodiversity Exploratories in Germany to disentangle the roles of land-use, management practices, soil properties, and microbial community in controlling microbial physiological responses. Results revealed that grasslands exhibited significantly higher microbial growth, respiration, and mass-specific respiration compared to forests, whereas CUE did not differ between land-use types. Within forests, tree composition greatly influenced microbial physiology, with deciduous stands demonstrating higher growth and CUE relative to coniferous stands. In grasslands, management exerted no direct influence on microbial traits, but altered soil nutrient status, which in turn positively affected CUE. In forests, management directly affected CUE and additionally shaped soil and microbial properties that mediated microbial physiological responses. Both soil and microbial properties were key determinants of microbial physiological traits, including growth, respiration, and CUE. However, the physiological responses were more consistent and pronounced in forests, whereas grasslands displayed more complex and trait-specific patterns. Overall, our findings demonstrate that microbial physiological traits emerge from the interplay between environmental conditions and microbial community composition, with distinct regulatory mechanisms across land-use types. These results highlight the critical role of land management and biodiversity in modulating soil microbial functioning and provide mechanistic insights into microbial physiology in terrestrial ecosystems.