The permafrost carbon inventory on the Tibetan Plateau: a new evaluation using deep sediment cores

• Published in: Global Change Biology
• Main Authors: Ding, Jinzhi, Li, Fei, Yang, Guibiao, Chen, Leiyi, Zhang, Beibei, Liu, Li, Fang, Kai, Qin, Shuqi, Chen, Yongliang, Peng, Yunfeng, Ji, Chengjun, He, Honglin, Smith, Pete, Yang, Yuanhe
• Other Authors: Yang, YH (reprint author), Chinese Acad Sci, Inst Bot, State Key Lab Vegetat & Environm Change, Beijing 100093, Peoples R China., Chinese Acad Sci, Inst Bot, State Key Lab Vegetat & Environm Change, Beijing 100093, Peoples R China., Univ Chinese Acad Sci, Beijing 100049, Peoples R China., Inner Mongolia Univ Technol, Hohhot 010051, Inner Mongolia, Peoples R China., Peking Univ, Dept Ecol, Beijing 100871, Peoples R China., Peking Univ, Key Lab Earth Surface Proc, Minist Educ, Beijing 100871, Peoples R China., Chinese Acad Sci, Inst Geog Sci & Nat Resources Res, Key Lab Ecosyst Network Observat & Modeling, Beijing 100101, Peoples R China., Univ Aberdeen, Inst Biol & Environm Sci, Aberdeen AB24 3UU, Scotland.
• Format: Journal/Newspaper
• Language: English
• Published: GLOBAL CHANGE BIOLOGY 2016
• Subjects: alpine permafrost; carbon-climate feedback; deep sediment; soil organic carbon stock; support vector machine; SOIL ORGANIC-CARBON; SUPPORT VECTOR MACHINES; CLIMATE-CHANGE; ARCTIC REGION; VEGETATION; CHINA; STORAGE; GRASSLANDS; SIBERIA; MATTER; Arctic; Climate change; permafrost; Siberia
• Online Access: https://hdl.handle.net/20.500.11897/434757; https://doi.org/10.1111/gcb.13257

The permafrost organic carbon (OC) stock is of global significance because of its large pool size and the potential positive feedback to climate warming. However, due to the lack of systematic field observations and appropriate upscaling methodologies, substantial uncertainties exist in the permafrost OC budget, which limits our understanding of the fate of frozen carbon in a warming world. In particular, the lack of comprehensive estimates of OC stocks across alpine permafrost means that current knowledge on this issue remains incomplete. Here, we evaluated the pool size and spatial variations of permafrost OC stock to 3m depth on the Tibetan Plateau by combining systematic measurements from a substantial number of pedons (i.e. 342 three-metre-deep cores and 177 50-cm-deep pits) with a machine learning technique (i.e. support vector machine, SVM). We also quantified uncertainties in permafrost carbon budget by conducting Monte Carlo simulations. Our results revealed that the combination of systematic measurements with the SVM model allowed spatially explicit estimates to be made. The OC density (OC amount per unit area, OCD) exhibited a decreasing trend from the south-eastern to the north-western plateau, with the exception that OCD in the swamp meadow was substantially higher than that in surrounding regions. Our results also demonstrated that Tibetan permafrost stored a large amount of OC in the top 3m, with the median OC pool size being 15.31 Pg C (interquartile range: 13.03-17.77Pg C). 44% of OC occurred in deep layers (i.e. 100-300cm), close to the proportion observed across the northern circumpolar permafrost region. The large carbon pool size together with significant permafrost thawing suggests a risk of carbon emissions and positive climate feedback across the Tibetan alpine permafrost region. National Basic Research Program of China on Global Change [2014CB954001, 2015CB954201]; National Natural Science Foundation of China [31322011, 41371213]; Chinese Acedemy of Sciences-Peking University Pioneer Collaboration Team; Thousand Young Talents Program SCI(E) PubMed ARTICLE [e-mail] 8 2688-2701 22