Temperature Sensitivity of Soil Respiration in Grasslands under the Temperate Continental Climate Zone: Analysis of 25-Year Monitoring Data

Abstract

Field observations of soil respiration (SR) in different types of terrestrial ecosystems seem to be very relevant, since the SR rate is characterized by high temporal and spatial variability. The intra-annual dynamics of SR is determined mainly by the change in hydrothermal conditions during the year and is often described using a temperature sensitivity coefficient (Q10), which usually has a fixed value in many of the models used. The aim of this study was to assess the seasonal and interannual dynamics of SR temperature sensitivity in two grasslands in the southern part of Moscow region (temperate continental climate) based on continuous 25-year year-round measurements of CO2 emissions from soils. Grasslands were formed on two different types of soils: soddy-podbur sandy soil (Entic Podzol (Arenic)) and gray loamy soil (Haplic Luvisol (Loamic)). The SR rate was measured continuously from December 1997 to November 2022 with an interval of 7–10 days using the closed static chamber method. The temperature sensitivity of SR, estimated from the entire set of data, had higher values on Haplic Luvisol compared to Entic Podzol (3.47 vs 2.59). The values of Q10 for SR in both types of soils in dry years were 1.2–1.4 times lower than in years with a normal moisture level. The interannual variability of Q10 values in grassland ecosystems was 21–36%, depending on the temperature range that was taken into account. A significant positive correlation between Q10 values in the temperature range ≥1°С and humidity indices was found in both grasslands. To obtain more accurate forecasts of the C balance in ecosystems, a differentiated approach should be applied by integrating different values of temperature coefficients for SR into the models.