Temperature Sensitivity of Soil Respiration in Palsa Peatlands of the North of Western Siberia

Palsa peatland soils are known as significant terrestrial storage of the Earth's soil carbon. The response of these soils to changing climate may result in a strong feedback to global carbon balance. In laboratory, we investigated the effect of rising temperatures on the upper (T1) and lower (T2) horizons of Turbic Histic Cryosols using sequential (S) and equal-time (ET) methods. The S method was applied to estimate the response of organic carbon mineralization rate (R) to sequential temperature increase from 5 to 30 degrees C; the ET method was used to study the response of the basal (microbial) respiration rate to equal-time incubation at 5, 15, and 25 degrees C. The Q(10) coefficient was calculated. In the T1 horizon, both methods (S and ET) demonstrated a positive response of respiration to the rise in temperature. The respiration intensity increased by 91 and 84%, respectively. In the T2 horizon, it increased by 93 and 91%, respectively. However, despite the overall positive response of soil respiration to the rise in temperature, the Q(10) values demonstrated differences in the temperature sensitivity of soil respiration. These values were maximal in the cold (5-15 degrees C) range for both horizons. For most of temperature ranges, Q(10) was higher for T2 than for T1. For the T1 horizon and S method, Q(10) slightly varied (2.7-3.0), whereas in the case of the ET method, it decreased by 3.3 times from the cold (4.9) to the warm 15-25 degrees C (1.5) temperature range. For the T2 horizon, the S method also did not cause significant shifts in Q(10) (3.0-3.5); the ET method caused a decrease in Q(10) by 1.5 times from the cold (4.3) to the warm (2.8) temperature range. To sum up, the ET method leads to a wider variation of Q(10) values in comparison with the S method thus indicating its better applicability for temperature sensitivity studies with palsa peatland soils under laboratory conditions.