Land-use drives the temporal stability and magnitude of soil microbial functions and modulates climate effects

Soil microbial community functions are essential indicators of ecosystem multifunctionality in managed land-use systems. Going forward, the development of adaptation strategies and predictive models under future climate scenarios will require a better understanding of how both land-use and climate disturbances influence soil microbial functions over time. Between March and November 2018, we assessed the effects of climate change on the magnitude and temporal stability of soil basal respiration, soil microbial biomass and soil functional diversity across a range of land-use types and intensities in a large-scale field experiment. Soils were sampled from five common land-use types including conventional and organic croplands, intensive and extensive meadows, and extensive pastures, under ambient and projected future climate conditions (reduced summer precipitation and increased temperature) at the Global Change Experimental Facility (GCEF) in Bad Lauchstädt, Germany. Land-use and climate treatment interaction effects were significant in September, a month when precipitation levels slightly rebounded following a period of drought in central Germany: compared to ambient climate, in future climate treatments, basal respiration declined in pastures and increased in intensive meadows, functional diversity declined in pastures and croplands, and respiration-to-biomass ratio increased in intensive and extensive meadows. Low rainfall between May and August likely strengthened soil microbial responses toward the future climate treatment in September. Although microbial biomass showed declining levels in extensive meadows and pastures under future climate treatments, overall, microbial function magnitudes were higher in these land-use types compared to croplands, indicating that improved management practices could sustain high microbial ecosystem functioning in future climates. In contrast to our hypothesis that more disturbed land-use systems would have destabilized microbial functions, intensive meadows and organic croplands showed stabilized soil microbial biomass compared to all other land-use types, suggesting that temporal stability, in addition to magnitude-based measurements, may be useful for revealing context-dependent effects on soil ecosystem functioning.