Abstract: This study aimed to compare the changes of soil respiration rate (Rs), autotrophic respiration rate (Ra), and heterotrophic respiration rate (Rh) across a nitrogen application gradient in an alpine meadow on the Qinghai-Tibet Plateau, reveal the main influencing factors of soil respiration and its components, and provide a scientific basis for evaluating soil carbon release from alpine meadows under future nitrogen deposition. In 2014, a nitrogen addition platform was established in the alpine meadow of the Qinghai-Tibet Plateau in Hongyuan, Sichuan, following a completely randomized block experimental design with six levels of nitrogen addition, including 0 (N0, control), 2 (N2), 4 (N4), 8 (N8), 16 (N16) and 32 (N32) g N·m^-2·a^-1. Nitrogen application significantly decreased soil respiration and its components (P<0.05), and Ra decreased more than Rh, resulting in a gradual increase of Rh/Rs with the nitrogen addition gradient. There were significant exponential positive correlations between Ra and Rh and soil temperature under different nitrogen addition treatments (P<0.05). Nitrogen addition decreased the temperature sensitivity (Q₁₀) of Ra, but increased that of Rh. The relationship between the components of soil respiration and soil moisture was not significant, but the two-factor model of soil temperature and soil moisture explained Ra and Rh better than the single-factor model. Our results enhance mechanistic understanding of soil respiration and its components in response to nitrogen addition in an alpine meadow, and provide a theoretical basis for evaluating the response of alpine meadow ecosystems to atmospheric nitrogen deposition and guiding ecosystem management.

Key words: alpine meadow, soil respiration, autotrophic respiration, heterotrophic respiration, temperature sensitivity