Juselius-Rajamäki Teemu, Väliranta Minna, Korhola Atte
Environmental Change Research Unit (ECRU), Ecosystems, Environment Research Programme, Faculty of Biological and Environmental Sciences, and Helsinki Institute of Sustainability Science (HELSUS), University of Helsinki, Helsinki, Finland.
Glob Chang Biol. 2023 Dec;29(24):7173-7191. doi: 10.1111/gcb.16988. Epub 2023 Oct 19.
Peatlands are the most dense terrestrial carbon stock and since the last glacial epoch northern peatlands have accumulated between 400 and 1000 Gt of carbon. Although the horizontal development history of the peatlands during the Holocene has been previously researched, these studies have overlooked the current peatland margins. This has led to a long-standing view that the lateral expansion of the peatlands has halted or significantly slowed down. However, no concentrated effort focusing on the recent development of the peatland margins has been conducted. To fulfil this knowledge gap, we studied the development of peatland margins in five Finnish peatlands. In addition, we studied the effect of peatland subsoil characteristics and past forest fires on the peatland expansion. We sampled 15 transects with a total of 47 peat cores utilizing C radiocarbon dating on the basal layers of these peat cores. Our results show that the Northern peatlands are still expanding with four of our study sites having recent, post-1950's basal ages in the peatland margins. In addition, the rate of peatland lateral expansion has increased during the last 1500 years in our study sites, challenging the current knowledge of the recent peatland expansion dynamics. We recorded lateral expansion rates of 0.1-6.4 cm/year from the sites studied. The rate of lateral expansion was restricted by local characteristics, especially the steepness of subsoil (p = .0108). Forest fires likely played an important role as the trigger for lateral expansion in southern study sites with large number of charcoal found at the basal layer of the peat cores. Depending on the scope of this recent lateral expansion across the vast northern peatlands, the effect on the carbon balance could be significant and should be taken into account when estimating the development of carbon pools in these crucial ecosystems.
泥炭地是密度最大的陆地碳库，自上一个冰川期以来，北半球泥炭地已积累了400至1000吉吨的碳。尽管此前已对全新世期间泥炭地的横向发育历史进行了研究，但这些研究忽略了当前的泥炭地边缘。这导致了一种长期存在的观点，即泥炭地的横向扩张已经停止或显著放缓。然而，尚未有人集中精力研究泥炭地边缘的近期发育情况。为了填补这一知识空白，我们研究了芬兰五个泥炭地边缘的发育情况。此外，我们还研究了泥炭地下层土壤特征和过去森林火灾对泥炭地扩张的影响。我们沿着15条样带采集了总共47个泥炭芯样本，并利用碳-14对这些泥炭芯的底层进行了年代测定。我们的研究结果表明，北半球的泥炭地仍在扩张，我们研究的四个地点的泥炭地边缘有1950年后的近期底层年代。此外，在我们的研究地点，泥炭地的横向扩张速度在过去1500年中有所增加，这对当前关于泥炭地近期扩张动态的认识提出了挑战。我们记录到所研究地点的横向扩张速度为0.1至6.4厘米/年。横向扩张速度受到当地特征的限制，特别是下层土壤的坡度（p = 0.0108）。在泥炭芯底层发现大量木炭的南部研究地点，森林火灾可能是横向扩张的重要触发因素。根据近期这种横向扩张在广阔的北半球泥炭地中的范围，其对碳平衡的影响可能很大，在估算这些关键生态系统中碳库的发展时应予以考虑。
