Seasonal Variability of Carbon Dioxide, Sensible and Latent Heat Fluxes in a Northern Taiga Larch Forest of Central Siberia for Eddy Covariance Flux Measurements

The seasonal and daily variability of sensible and latent heat and carbon dioxide (CO 2 ) fluxes, as well as the sensitivity of the fluxes to changing environmental conditions were derived by the eddy covariance flux measurements in an undisturbed northern-taiga larch forest on continuous permafrost in Central Siberia from the end of May to the end of September in 2013 and 2015. The measurements showed a high seasonal and daily variability of CO 2 , sensible and latent heat fluxes. It was found that whereas dry and sunny weather conditions of June and July in 2013 and 2015 resulted in lower daily latent heat fluxes as compared to sensible ones, mostly cloudy and rainy weather in the second half of the summer led to the reduced net radiation and increased latent heat fluxes. The daily values of gross primary production from the beginning of June to mid-August in 2013 and 2015 exceeded the values of the ecosystem respiration, and the forest ecosystem was the sink of CO 2 from the atmosphere. The maximum CO 2 uptake was observed in late June and early July, primarily due to high photosynthesis rates influenced by high incoming solar radiation, optimal air temperature, and soil moisture conditions. Since mid-August, the balance between the CO 2 uptake and release was close to zero. The total net ecosystem CO 2 exchange during the growing season of 2013 was –76.5 g C/m 2 , while it was slightly higher (–103.6 g C/m 2 ) during the growing season of 2015, primarily due to higher air temperatures in June and greater precipitation in the summer months of 2015.