ABSTRACT

This study examines the Holocene evolution of an inland subarctic permafrost peatland located on the north bank of Wiyâshâkimî Lake (Nunavik, northeastern Canada). The analysis of plant macrofossils allowed us to reconstruct the succession of the trophic conditions of a palsa and a filled thermokarst pond. The accumulation of organic matter began at around 6290 cal. y BP. The evolution of the site then followed three stages: a pond (6290–5790 cal. y BP), a minerotrophic peatland (5790–4350 cal. y BP) and an ombrotrophic peatland (from 4350 cal. y BP). The establishment of permafrost caused a palsa to form at around 170 cal. y BP, which corresponds to the coldest period of the Little Ice Age in northeastern Canada. A subsequent degradation of the palsa and the formation of a thermokarst pond were induced by the climate warming that began at the turn of the 20th century. The analysis of plant macrofossils from an adjacent filled thermokarst pond indicated three phases of development over a short 450-year period: subaquatic, minerotrophic, and ombrotrophic phases. When combined with previous studies of filled thermokarst ponds in northern Québec, this result indicates that ponds are rapidly filling in with vegetation and acting as carbon sinks.

摘要

本研究考察了位于 Wiyâshâkimî 湖（加拿大东北部努纳维克）北岸的内陆亚北极永久冻土泥炭地的全新世演化。对植物大型化石的分析使我们能够重建 palsa 和充满热岩溶池的营养条件的连续性。有机物的积累开始于 6290 卡路里左右。y 血压。该场地的演变经历了三个阶段：池塘（6290-5790 cal. y BP）、矿质泥炭地（5790-4350 cal. y BP）和嗜碱性泥炭地（4350 cal. y BP）。永久冻土的形成导致 palsa 在大约 170 cal 时形成。y BP，对应于加拿大东北部小冰河时代最冷的时期。20 世纪初开始的气候变暖导致了随后的 palsa 退化和热岩溶池的形成。对来自相邻填充的热岩溶池塘的植物大体化石的分析表明，在短短 450 年的时间内经历了三个发展阶段：水下、矿质和盐生阶段。结合之前对魁北克北部填充热岩溶池塘的研究，该结果表明池塘正在迅速填满植被并充当碳汇。