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Ecological Assessment of Temperature's Influence on CO2 Efflux from Lawn Soils in Case of Its Pronounced Dynamics
The carried-out microfield model research was aimed at identifying patterns in the dynamics of soil CO2 effluxes depending on the locally occurring hydrothermal regimes of regenerated lawn ecosystems on peat-sand substrates with different peat contents. Monitoring was carried out every ten days from 21 April 2019 to 30 October 2019 and included measurements of soil and air temperature, soil moisture, and CO2 efflux every 3 h during the day. The weather conditions of the 2019 growing season in Moscow, with air temperature close to the annual average and increased precipitation, made it possible to clarify quantitative patterns of the temperature influence on CO2 efflux from lawn soils in case of their pronounced dynamics without real soil moisture deficit. To study relationships between CO2 efflux and soil and air temperatures, three empirical CO2 efflux models (Exponential, Raich-Hashimoto and Lloyd-Taylor) were used with comparative assessment of their results. The conducted investigation showed that both peat content, local hydrothermal regime, and type of vegetation cover play a significant role in efflux modulation, with the temperature factor dominating on both seasonal (72% impact) and intraday (51-94% impact) scales. The lawn substrate factor accounts for up to 10% of CO2 efflux variability on the intraday scale. The lawn vegetation cover (with the lower and higher diversity) significantly affects the soil hydrothermal regime depending on the peat content (a higher impact with a lower peat content due to the soil pH difference). The denser vegetation reduces the soil temperature, providing better protection, and at the same time reduces soil moisture by transpiration, which provides the combined effect on the CO2 efflux reduction (up to 1 g CO2 m −2 day −1 reduction for the lower-pH soils).