Hummocks in alpine tundra, northern British Columbia, Canada: distribution, morphology and organic carbon composition

Arctic Science

article

Marjolaine Verret¹  Yifeng Wang¹  Jean Bjornson¹  Denis Lacelle¹ 

[1] Department of Geography, University of Ottawa;School of Geography, Environment and Earth Sciences, Victoria University

关键词: cryoturbation;    organic carbon;    permafrost;    subarctic.;   

DOI  :  10.1139/as-2018-0021

学科分类：地球科学(综合)

来源: NRC Research Press

【 摘 要 】

Hummocks develop by cryoturbation in fine-grained frost-susceptible soils and their stage of maturity may affect the translocation of organics in Cryosols. This study examines the distribution and morphology of hummocks in the Chuck Creek Trail Valley (northern British Columbia) and determines the quantity, distribution, and composition of organic matter in their soils. Hummocks occupy about 5%–20% of the valley and their morphology is largely affected by their silt content. Cryoturbated intrusions, radiocarbon dated to 2814 and 1648 cal year B.P., suggest that hummock development was initiated during the cooler late Holocene. Hummocks have an average soil organic carbon density of 16.3 kg m −2 in the uppermost 1 m, with 62% stored in the top 25 cm. Organics are mainly present as particulate organic matter in the O-horizon (25%–80%), characterized by degradable alkyl C and O/N-alkyl groups, but occur as mineral-associated organic matter (96%–98%) composed of recalcitrant aromatic and aliphatic C groups in the underlying B and C horizons. Minor differences in organic content and composition occur between hummock tops and troughs, and between hummocks showing different stages of maturity. In the absence of an observed frost table, contemporary hummock activity is attributed to seasonal freezing and thawing.

【 授权许可】

CC BY