Responses of CO2 efflux from an alpine meadow soil on the Qinghai Tibetan Plateau to multi-form and low-level N addition

Aims To assess the effects of atmospheric N deposition on the C budget of an alpine meadow ecosystem on the Qinghai–Tibetan Plateau, it is necessary to explore the responses of soil-atmosphere carbon dioxide (CO 2 ) exchange to N addition. Methods Based on a multi-form, low-level N addition experiment, soil CO 2 effluxes were monitored weekly using the static chamber and gas chromatograph technique. Soil variables and aboveground biomass were measured monthly to examine the key driving factors of soil CO 2 efflux. Results The results showed that low-level N input tended to decrease soil moisture, whereas medium-level N input maintained soil moisture. Three-year N additions slightly increased soil inorganic N pools, especially the soil NH 4 + -N pool. N applications significantly increased aboveground biomass and soil CO 2 efflux; moreover, this effect was more significant from NH 4 + -N than from NO 3 − -N fertilizer. In addition, the soil CO 2 efflux was mainly driven by soil temperature, followed by aboveground biomass and NH 4 + -N pool. Conclusions These results suggest that chronic atmospheric N deposition will stimulate soil CO 2 efflux in the alpine meadow on the Qinghai–Tibetan Plateau by increasing available N content and promoting plant growth.