Differences of soil CO_2 flux in two contrasting subalpine ecosystems on the eastern edge of the Qinghai-Tibetan Plateau: A four-year study

摘要

Alpine and subalpine ecosystems on Qinghai-Tibetan Plateau are rich in soil organic carbon and are among the most sensitive regions to climate change, while little is known about the dynamics of soil carbon dioxide (CO2) in alpine/subalpine ecosystems except for the grassland on the plateau. In this study, the monthly and inter-annual variations in soil CO2emission from a subalpine coniferous forest and a subalpine shrubland ecosystem on the eastern edge of the Qinghai-Tibetan Plateau were investigated from 2012 to 2015 using the opaque steady-state chamber method. Soil CO2flux rate during the growing season ranged from 153.3 to 683.6 mg m−2h−1in the coniferous forest, being twice of that (76.6–347.3 mg m−2h−1) in the shrubland, due to the elevation-induced differences in soil temperature and water content and the vegetation-induced differences in soil carbon and nitrogen pools. Both ecosystems showed large monthly variations in soil CO2flux rate, while relative to the coniferous forest, the shrubland had a less inter-annual variation in soil CO2emission. The two ecosystems had the same temperature sensitivity of soil CO2emission, which suggests that they will respond similarly to global warming concerning soil CO2flux rate. The results highlight the importance of soil CO2emission in subalpine forest and shrubland ecosystems, which can be helpful to reduce the uncertainty of regional estimates of carbon budget in subalpine regions under global warming.