Carbon dioxide emission from temperate semiarid steppe during the non-growing season

Clarifying whether grazed semiarid steppe is a sink or source of carbon dioxide (CO2) requires accurate quantification of the annual net CO2 exchange between the ecosystem and the atmosphere. Previous studies have primarily focused on the growing season and on single grazing pattern. Carbon dioxide emission from the temperate semiarid steppe during the non-growing season and its responses to various grazing practices still remains uncertain. Using the chamber-based technique, we simultaneously determined the CO2 fluxes during the non-growing season at twelve grazed semiarid temperate steppe plots in Inner Mongolia and investigated the responses of CO2 emission to different grazing practices. The CO2 fluxes during the non-growing season were demonstrated to be significantly regulated by soil temperature and moisture contents. The cumulative CO2 emission during the non-growing season (October–April) amounted to 353 ± 26 kg C ha−1 on average (ranges: 180–484 kg C ha−1), significantly demonstrating decrease with increasing grazing intensity and increase with mean snow cover depth or mean surface soil moisture content. The empirical equations describing these significant relationships provide simple approaches to estimate the regional amounts of CO2 emission from temperate semiarid steppe during the non-growing season.

► Soil temperature determined the seasonality of CO2 flux.
► The CO2 emission could occur at soil temperature of −5 °C at steppe.
► Grazing decreased total CO2 emission during the non-growing season.