Gas exchange in sphagnum mosses at different near-surface groundwater levels

Abstract

Studies performed in a southern taiga pine bog forest under different temperature and moisture conditions have shown that the dependence of sphagnum CO2 exchange on environmental factors is largely regulated by near-surface groundwater level (GWL). When the GWL is at a depth of 4–7 cm, CO2 uptake by sphagnum increases with rise in temperature; at a GWL depth of 21 cm, CO2 emission (instead of uptake) takes place, decreasing at higher temperatures. As the GWL descends and air temperature rises, CO2 becomes higher. At a GWL depth of more than 43 cm, the influence of temperature decreases and CO2 emission drops by more than half. The dependence of sphagnum CO2 exchange on solar radiation is also ambiguous. This dependence is logarithmic at a GWL depth of 4 to 21 cm, but at the latter level sphagnum mosses release CO2 rather than absorb it, with CO2 emission decreasing significantly at an irradiance of more than 200 W/m2. Sphagnum CO2 exchange at GWL below 30 cm is independent of solar irradiance, and further increase in GWL depth leads to reduction in CO2 emission.