Partitioning of net ecosystem exchange using chamber measurements data from bare soil and vegetated sites

A model of net ecosystem exchange (NEE) was suggested to study the influence of different environmental factors and to calculate daily and annual carbon budget. The model uses air temperature, incoming photosynthetically active radiation, vapor pressure deficit, and leaf area index as the explanatory factors for gross primary production, heterotrophic and autotrophic respiration. The model coefficients were calibrated using data collected by automated soil carbon dioxide (CO2) flux system with clear long-term chamber at an urban grassland in Tomsk, Russia. Observation results obtained at two sites (bare soil and vegetated) allows to calculate the temperature sensitivity for soil and plant respiration. Revealed fast and slow responses of soil respiration to temperature contribute together to the pulsed behavior of heterotrophic respiration. The total annual NEE resulted in 163.5 g C m−2. Growing plants accumulate 522.7 g C m−2 in total, but the net annual release of CO2 is higher (686.2 g C m−2). The studied ecosystem is a source of carbon according to modelling and observation results. Results indicate that the suggested model is a promising tool for a better understanding of ecosystem biogeochemical processes.