Fluxes of CO 2 , CH 4 , and N 2 O in tundra-covered and Nothofagus forest soils in the Argentinian Patagonia

Abstract

While most soils in periglacial environments present high fluxes of CO 2 (F CO2 ), CH 4 (F CH4 ), and N 2 O (F N2O ), few of them have a tendency to drain greenhouse gases from the atmosphere. This study aimed to assess greenhouse gas fluxes at different sub-Antarctic sites and time periods (at the beginning of thaw and height of summer). To investigate the time of year effect on greenhouse gas emissions, F CO2 , F CH4 , and F N2O were measured at two sites tundra-covered (Ti and Th) and Nothofagus forest soil (Nf) on Monte Martial, at the southernmost tip of South America, Tierra del Fuego, Argentina. F CO2 ranged from 96.33 to 225.72 μg CO 2 m −2 s −1 across all sites and periods, showing a positive correlation with soil temperature (Ts) (4.1 and 8.2 °C, respectively) (r 2 > 0.7; p < 0.05). The highest values of F CO2 were found at Ti and Th (728.2 and 662.64 μg CO 2 m −2 s −1 , respectively), which were related to higher temperatures (8.2 and 8.6 °C, respectively) when compared to those of Nf. For F CH4 , the capture (drain) occurred during both periods at Nf (−26 and −79 μg C–CH 4 m −2 h −1 ) as well as Ti and Th (−21 and 12 μg C–CH 4 m −2 h −1 , respectively). F N2O also presented low values during both periods and showed a tendency to drain N 2 O from the atmosphere, especially at Nf (−2 μg N–N 2 O m −2 h −1 ). In addition, F N2O was slightly positive for Ti and Th (0.3 and 0.55 μg N–N 2 O m −2 h −1 , respectively). Soil moisture did not show a correlation (p > 0.05) with the measured greenhouse gas fluxes. A scenario of increased temperatures might result in changes in the balance between the emissions and drains of these gases from soils, leading to higher emission values of CH 4 and N 2 O, especially for tundra covered soils (Ti and Th), where the highest average fluxes and thermohydric variations were observed over the year.