Abstract: The intensification of climate change and human activities has led to an increase in exogenous nitrogen input in alpine ecosystems, resulting in an increase in carbon emissions. In this study, with a database of 30 papers related to Qinghai-Tibet Plateau alpine ecosystems, a meta-analysis was performed to evaluate the response of soil respiration in alpine ecosystems to N addition. N addition had a significant positive effect on soil respiration in alpine ecosystems (P<0.05). N addition rate dominated the positive/negative effect on soil respiration, in that  ≤200 kg N·hm^-2·a^-1 significantly promoted soil respiration, and the promotion of soil respiration at >200 kg N·hm^-2·a^-1 was significantly weakened. There was a 2-year threshold value for the positive effect of N addition duration on soil respiration (P<0.05), in that >2-year N addition significant decreased the positive effect of N addition on soil respiration. The differences in the positive effects of N addition on soil respiration in different alpine ecosystems were significant (P<0.05), i.e., subalpine forest > alpine meadow > alpine swamp wetland. The positive effect of N addition on soil respiration was mostly significant in an average annual temperature >2 ℃, or annual precipitation >800 mm, or altitude ≤3000 m in Qinghai-Tibet Plateau alpine ecosystems. This study can provide theoretical and practical basis for ecological protection in alpine vulnerable areas of China.

Key words: Qinghai-Tibet Plateau, alpine ecosystem, soil CO₂ emission, nitrogen input, meta analysis