Rhizosphere priming of soil organic matter in response to multiple global change factors

The rhizosphere priming effect (RPE), referring to the effects of living plant roots on soil organic matter decomposition, plays an important role in terrestrial carbon and nutrient cycling. However, how global changes may affect RPE remains unclear. By conducting a global meta-analysis of 220 observations from 39 plant species planted in 49 mineral and organic soils, we quantified the effects of multiple global change factors on RPE and explored the regulations of plant, edaphic, and experimental factors on RPE responses. We found that, overall, nitrogen addition, phosphorus addition, elevated CO₂, warming, increased precipitation, or nitrogen addition plus elevated CO₂ had a neutral effect on RPE, while nitrogen plus phosphorus addition significantly decreased RPE. The responses of RPE and plant biomass were decoupled under all these global change factors. Across studies, the elevated CO₂ effect on RPE increased significantly with soil nitrogen availability but decreased with soil clay plus silt content under ambient nitrogen, but these relationships disappeared under elevated nitrogen. Similarly, the warming effect on RPE increased with soil nitrogen availability. Our findings suggest that, when considered from the perspective of individual GCFs, global change may not have a substantial impact on the rhizosphere priming effect.