What are the fluxes of CH4, CO2 and N2O and their relationships with environmental factors in the alpine wetland and alpine grassland of the Tianshan Mountains

Global mean surface temperature has increased over the last century by approximately 0.7°C. Annual mean temperature will continue to rise more rapidly in the coming decades as a result of increasing greenhouse gases concentration. Methane (CH₄), carbon dioxide (CO₂) and nitrous oxide (N₂O) are considered as the important greenhouse gases that play important roles in climate warming.

Wetlands cover about 5% of the global land surface, and the ecosystems contribute significantly to the global greenhouse gases budget. However, there is a lack of information about emissions of CH₄, CO₂ and N₂O in the alpine wetland of the Tianshan Mountains up to now. Furthermore, researches about the fluxes of CH₄, CO₂ and N₂O in the alpine grassland of the mountains are also scarcely.

To evaluate the flux differences of CH₄, CO₂ and N₂O between the alpine wetland and alpine grassland, and to determine the effects of environmental factors on CH₄, N₂O and CO₂ fluxes in the Tianshan Mountains, LI Kaihui et al. conducted a field experiment in the growing season (from May to October) of 2010 to 2012 in the Bayinbuluk Grassland Eco-system Research Station, Chinese Academy of Sciences.

In the Tianshan Mountains, the average flux values of CH₄, CO₂ and N₂O in the alpine wetland were higher than those in the alpine grassland. The alpine wetland acted as the source of CH₄ while the alpine grassland acted as the sink of CH₄. However, both the alpine wetland and alpine grassland are sources of N₂O. All the fluxes of CH₄, CO₂ and N₂O showed large seasonal and annual variations with strong fluxes occurring in the growing season while weak fluxes occurring in the non-growing periods.

Environmental factors including air temperature, precipitation, soil temperature and soil water content greatly influenced the CH₄, N₂O and CO₂ fluxes. Relationships between CH₄ fluxes and environmental factors indicated that CO₂ fluxes were significantly positively and negatively correlated with soil temperature, air temperature and soil water content in the alpine wetland and alpine grassland, respectively. However, for CO₂ and N₂O fluxes, they were all significantly positively correlated with these environmental factors both in the alpine wetland and alpine grassland.

The findings of the study can improve a reference for understanding the fluxes of greenhouse gases in the high-altitude of the Tianshan Mountains. The study was published in Journal of Arid Land in December 2014.