Global effects on soil respiration and its temperature sensitivity depend on nitrogen addition rate

Soil respiration (Rs) plays a crucial role in regulating carbon (C) cycling in terrestrial ecosystems and the atmospheric carbon dioxide (CO2) concentration. However, the impact of nitrogen (N) addition on Rs and its temperature sensitivity (Q10) is poorly understood. Here, we used 1413 paired observations from 261 studies to explore how N addition affects Rs and its Q10 across terrestrial ecosystems on a global scale. Nitrogen addition increased autotrophic respiration in croplands, deserts and shrublands, but decreased it in grasslands, forests (including coniferous and deciduous forests) and wetlands. In contrast, N addition increased heterotrophic respiration in grasslands, wetlands and deserts, but decreased its Q10 across different ecosystem types other than deserts. Nitrogen addition decreased (p