[M-IS01] ENVIRONMENTAL, SOCIO-ECONOMIC, AND CLIMATIC CHANGES IN NORTHERN EURASIA

[MIS01-07] The different response of CO₂ fluxes to extreme weather conditions of ecosystems in the tropics, mid-latitudes and polar regions.

*Daria Gushchina¹, Maria Tarasova¹, Elizaveta Satosina^1,2, Irina Zheleznova¹, Ekaterina Emelianova^1,2, Ravil Gibadullin¹, Alexander Olchev¹ (1. Department of Meteorology and Climatology, Faculty of Geography, Lomonosov Moscow State University, GSP-1, Leninskie Gory, 1, Moscow 119991, Russia, 2. A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Science, Leninsky Prospekt 33, Moscow 119071, Russia)

Keywords:polar temperate tropical zones, CO2 fluxes, temperature and precipitation anomalies, FLUXNET

The effects of anomalous weather conditions (such as extreme temperatures and precipitation) on the variability of CO₂ fluxes in different ecosystems of the polar, temperate and tropical zones were assessed using available reanalysis data as well as information on daily net CO₂ fluxes from the global FLUXNET database. 18 stations in the polar zone, 40 stations in mid-latitudes and 17 stations in the tropics were analyzed, while only the warm season in the temperate and polar zones was analyzed to ensure comparability with the tropics. Extreme temperature and precipitation periods were defined as periods when the daily mean temperature anomaly and daily precipitation amount exceeded the 95% quantile (for extremely high temperatures and precipitation) or did not reach the 5% quantile (for extremely low temperatures) of the probability density function (PDF). The normal distribution for air temperature and Weibull distribution for precipitation was used in our study as the most appropriate for long-term time series analysis
The main difference between the response of CO₂ fluxes to extreme weather conditions in the tropics and mid-latitudes and polar regions is the dominant influence of precipitation anomalies in the tropics and the dominant influence of temperature anomalies in the extratropical regions.
The meteorological conditions unfavorable for the growth and development of ecosystems in polar, temperate and tropical latitudes were identified. It was found that in temperate and polar regions, the most unfavorable conditions for plant photosynthesis are extremely high temperatures and precipitation - in all ecosystems studied, these events lead to an increase in CO₂ emissions into the atmosphere. High temperatures tend to suppress photosynthesis and reduce primary production in ecosystems. However, the strongest immediate effect of intense precipitation is due to increased rates of decomposition of soil organic matter and autotrophic and heterotrophic respiration during wet periods. In tropical latitudes, a similar response to heavy precipitation is observed - an increase in CO₂ emissions to the atmosphere in all ecosystems except savannas, which is associated with the same mechanisms as in extratropical latitudes. The response of CO₂ fluxes in the tropics to extremely high temperatures is opposite to that in temperate and polar latitudes, with an increase in CO₂ uptake by ecosystems during hot periods. This response differs significantly from some previously documented relationships (e.g., higher CO₂ emissions under drier and hotter weather, higher CO₂ uptake under colder and wetter weather) and results from the fact that, under sufficient soil moisture conditions, abnormally high temperature was not a limiting factor for the functioning of plant communities and, together with high amounts of incoming solar radiation in low-cloud weather, contributed to the intensification of the photosynthetic rate. The response to temperature decreases is ambiguous even within the same biome, i.e. the percentage of days with positive and negative CO₂ flux anomalies on days with low temperatures is almost the same. This is characteristics both of the tropics and extratropical regions. A clear predominance of CO₂ emissions is observed only in larch forests of temperate latitudes and in seasonal dry forests (caatinga) and permanent wetlands in tropics.

This research was funded by the Russian Science Foundation, grant number 22-17-00073.