Changes in net CO2 uptake, photosynthesis, and ecosystem respiration and their relationships with climate and snow characteristics in central Siberia

Abstract

<p>Anomalous or extreme climate conditions in high northern latitudes are likely to become more frequent and intense for the last several years. Based on the eddy covariance flux data from 2013-2017 collected at a boreal forest and peatland in central Siberia, net CO<sub>2</sub> uptake in spring 2015 was the highest compared with the 2013-2017 average because of the anomalous surface warming over the region > 60N. This enhanced spring net CO<sub>2</sub> uptake may be associated with more snowfall amount in winter. However, an increased spring net CO<sub>2</sub> uptake may be compensated with summertime net CO<sub>2</sub> uptake due to the relatively cool summer surface temperature in 2015. Spring 2020 in central Siberia has experienced even more substantial surface warming than in spring 2015, probably associated with excessive spring snowmelt. This suggests that further investigations in the effects of anomalous seasonal climate and snow conditions on net CO<sub>2</sub> uptake, photosynthesis and ecosystem respiration are necessary to better understand annual CO<sub>2</sub> balance. To characterize carbon fluxes and underlying mechanisms related to climate condition and snow characteristics from 2012-2020, we analyzed upscaling carbon flux dataset based on a random forest model by Jing et al. (2021), satellite-based net ecosystem exchange of CO<sub>2</sub> (i.e., Soil Moisture Active Passive (SMAP) L4 data), snow characteristics (e.g. freeze-thaw cycle, snow depth), and reanalysis dataset. We will focus on seasonal CO<sub>2</sub> uptake, photosynthesis and ecosystem respiration under the anomalous temperature and snowfall/snowmelt conditions, then discuss factors regulating annual net CO<sub>2</sub> uptake capacity in boreal forests and peatlands in central Siberia.</p>