Shrub encroachment drives different responses of soil respiration to increased precipitation and N enrichment

•Increased precipitation promotes soil respiration in moderate shrubby steppe.•Soil respiration in severe shrubby steppe is insensitive to water and N addition.•Soil respiration in response to resource changes depends on shrub invasion stage.•Soil respiration in shrub-encroached steppe is dominated by water availability.•Biotic drivers shift from plant community to microbial community as shrub-invasion.