Decomposition of Permafrost Carbon with Increasing Incubation Temperature on the Qinghai-Xizang (Tibetan) Plateau

Abstract:

Little is currently known about the decomposition of deep-permafrost organic carbon on the Qinghai-Xizang (Tibetan) Plateau (QXP) with increasing temperature. We studied the effect of temperature on CO₂ emissions from soil, from the active layer to deep permafrost (400 cm), during a 140-day incubation at temperatures of −5.0 °C to +5.0 °C. We found that permafrost carbon emissions on the QXP increase with soil temperature. Temperature has greater impact on soil organic carbon (SOC) decomposition in permafrost soils than in thawed soils. A temperature increase of 4.5° results in an average increase in carbon release of 482.8% (±60%) at temperature below 0 °C (−5.0 to −0.5 °C), and 102.0% (±37.5%) at temperatures above 0 °C (0.5 to 5.0 °C). Permafrost carbon has greater vulnerability at subzero temperatures than at temperature above 0 °C. Moreover, the increase in permafrost carbon release in mineral soils was larger than that in organic soils at temperatures form −5.0 to −0.5 °C. The released CO₂ mostly came from soils at depths of 10−20 cm and deep permafrost soils at depths of 245−255 cm and 285−295 cm, based on the stable carbon isotope analysis of δ¹³SOC and δ¹³CO₂.