EFFECTS OF TEMPERATURE AND PRECIPITATION ANOMALIES ON CARBON DIOXIDE FLUXES IN THE EXTRATROPICAL FORESTS OF THE NORTHERN HEMISPHERE

Abstract

Modern climate change, accompanied by rapidly increasing global air temperature, changing precipitation patterns, frequency and severity of extreme weather events, may have a significant impact on the functioning, growth, and development of forest ecosystems. The aim of the study was to assess the effects of extreme weather events (significant positive and negative anomalies in air temperature and precipitation) on the carbon dioxide (CO2) fluxes in boreal and temperate forest ecosystems in the Northern Hemisphere. 26 greenhouse gas (GHG) flux monitoring stations of the global FLUXNET network with the most continuous observations were selected for the analysis of CO2 fluxes. The stations are located in forest ecosystems of different biome types according to the IGBP classification. Meteorological conditions were analyzed using observations from meteorological stations and ERA5 reanalysis data. The results showed that the response of CO2 fluxes to temperature and precipitation anomalies varies depending mainly on the type of forest ecosystem, its geographical location and regional climatic conditions. Extremely high air temperature in any season leads to increased CO2 emissions to the atmosphere in all forest types studied, with the most pronounced response in coniferous forests. Negative air temperature anomalies in the warm season could have the opposite effect, either increasing or decreasing the CO2 uptake by forest ecosystems, depending on the forest ecosystem type. No significant response of CO2 fluxes to extremely low temperatures in the cold season was found. During periods of heavy precipitation, the emission of CO2 to the atmosphere dominated in all forest ecosystems under study. At the same time, after a large amount of precipitation during the warm season, a cumulative effect of available soil moisture in the plant root zone on CO2 fluxes was revealed. As a result the CO2 uptake by vegetation increases due to the growing rate of plant photosynthesis under sufficient soil moisture conditions.