CO 2 emissions from soils of different depths of a permafrost peatland, Northeast China: response to simulated freezing–thawing cycles

• Published in: Journal of Plant Nutrition and Soil Science
• Main Authors: Wang, Jiaoyue, Song, Changchun, Hou, Aixin, Wang, Lili
• Other Authors: Chinese Academy of Sciences, National Natural Science Foundation of China, CAS/SAFEA International Partnership Program for Creative Research Teams
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2014
• Subjects: permafrost
• Online Access: http://dx.doi.org/10.1002/jpln.201300309; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjpln.201300309; https://onlinelibrary.wiley.com/doi/pdf/10.1002/jpln.201300309

Abstract Soil freezing–thawing cycle (FTC) is an important factor controlling C dynamics in mid–high latitude regions, especially in the permafrost regions impacted by global warming. Nonetheless, the response of C cycling in the deeper active layers of permafrost regions to FTC remains far from certain. We aimed to characterize the emission of CO 2 from soils of multiple depths as impacted by FTC and its relationship with active organic C (OC) and enzyme activities. We collected soil samples from three soil layers (0–15, 15–30, and 30–45 cm) of an undisturbed peatland in the Da Xing'anling Mountains, NE China, and then subjected them to various freezing (10 to –10°C) and thawing (–10 to 10°C) cycles. Soil CO 2 emissions, two active OC fractions, and activities of three enzymes were monitored during incubation periods. At the thawing stage of the first FTC, CO 2 emission rates in the three soil layers presented transient peaks being ≈ 1.6–1.7 times higher than those of the unfrozen control sample. Although FTC did not change the overall patterns of decreasing CO 2 emission along the soil profile, FTC significantly reduced the amount of CO 2 emission when compared with the unfrozen control sample, possibly because the small CO 2 emission at the freezing stage neutralized the peak of CO 2 emission at the thawing stage. This study suggests that in the active layer of permafrost peatlands, CO 2 emission during FTCs may be lower than the emission under higher temperatures, but experiment with more temperature gradients should be encouraged to verify this conclusion in the future. Meanwhile, FTC significantly increased water extracted OC release from the three soil layers, ≈ 1.2–1.6 times higher compared to the unfrozen control sample, indicating that soil carbon loss in the form of leachate may increase during freezing–thawing periods. Additionally, the CO 2 emissions impacted by FTCs were significantly correlated with active OC fractions and enzyme activities, which indicated that active OC and enzymes were ...