Temperature Control of Spring CO2 Fluxes at a Coniferous Forest and a Peat Bog in Central Siberia

Measurements of vegetation CO2 uptake in northern Eurasia are crucial to understanding the carbon cycle in the boreal ecosystem. However, the currently available direct CO2 flux measurement datasets are still insufficient, particularly over central Siberia, thus it is still limited to understand the current status of the carbon cycle. We report daily and seasonal interannual variations in CO2 fluxes and associated abiotic factors measured using eddy covariance in a coniferous forest and a bog near Zotino, Krasnoyarsk Krai, Russia, for April to early June, 20132017. Both ecosystems became weak net CO2 sinks although the snow has not completely melted. Zotino forest became a net CO2 sink 716 days earlier than the Zotino bog. After the surface soil temperature exceeded ~1 C, both ecosystems became persistent net CO2 sinks. To completely change into the net CO2 sources to net CO2 sinks, both ecosystems seem to require certain levels of accumulated daily mean air temperature. Seasonal variations in cumulative net ecosystem exchange of CO2 at the bog were smaller than at the forest, implying that forests appear more sensitive to the rise of air temperature than bogs. Compared with other years, both ecosystems showed the highest net ecosystem productivity in 2015 because of the anomalously high air temperature in May. We also confirmed that cold spring weather conditions suppressed the spring CO2 uptake capacity than the warm spring weather conditions. Our study provides insights for predicting seasonal CO2 exchange and annual CO2 balance in boreal ecosystems under the warmer and drier northern Eurasia.