北極出現了新的碳匯？

 原文網址：https://www.helsinki.fi/en/news/climate-change/are-new-carbon-sinks-appearing-arctic

全球暖化會造成泥炭地植被在北極擴張。一組國際研究團隊發現了「原始泥炭」(proto-peat)的跡象，或許代表了新的泥炭地正在形成。

在這根土壤樣品中，黑色的部分代表了礦質土，棕色/綠色的地方則是有機質，大部分為苔蘚。圖片來源：Sanna Piilo

2018年，一組國際研究團隊在斯瓦爾巴(隸屬於挪威)Isfjorden峽灣附近三個地方鑽取了土壤樣品。他們在每個採樣地點都看到了同樣的現象：礦質土上方蓋了一層薄薄的有機質。換句話說，這層土壤含有許多光合作用從大氣當中抽取出來的碳。

由赫爾辛基大學的研究員Minna Väliranta主持的研究團隊將這種堆積中的有機土命名為「原始泥炭」(proto-peat)，其組成大部分是苔蘚，它們因為北極的氣候逐漸變暖而開始出現。

「雖然從定義上它們還不算真正的泥炭，但可以說他們正處於泥炭形成過程中的開端，」任職於赫爾辛基大學生物環境科學院的Väliranta表示。研究團隊還包括了Väliranta指導的博士研究員Teemu Juselius與Sanna Piilo。

這種原始泥炭沉積物也引起了國際上的興趣。Väliranta參與了一個更大型的計畫，經費來自英國自然環境研究委員會(NERC，相當於芬蘭科學院)。該計畫剛好也在探討同一現象，也就是全球暖化是否已經讓泥炭地植被擴張到北極。而這些植被的擴張又屬於一種更加全面的現象「北極綠化」(arctic greening)，一般是指隨著維管束植物擴張到之前無法生長的地方，北極開始有越來越多灌木生長。

「如果產生原始泥炭的作用在許多地方都在發生，那麼這些可以緩和氣候變遷的植物群集——也是一種意想不到的碳庫——或許正在北方逐漸建立起自己的地盤。由於模擬生態系和大氣的傳統模型並不認為有新的泥炭地正在形成，所以這些碳庫從來沒有被考慮進去，」Väliranta特別指出。

雖然氣候—生態系模型一直都在持續演進，但到了最近才有人試著把泥炭地的影響囊括到這類模型當中。

「如果要更準確地預測生態系在暖化的氣候之下如何運作，這些新發現的碳匯是模型必須考慮的新要素，」Väliranta表示。

 

Are new carbon sinks appearing in the Arctic?

Global warming can result in the spread of peatland vegetation in the Arctic. An international research group has discovered signs of ‘proto-peat’, which may be the beginning of new peatlands.

In 2018, an international research group bored for soil samples in three sites around the Isfjorden fjord in Svalbard, which is part of Norway. The same phenomenon was seen each boring site: mineral soil covered by a thin layer of organic matter. In other words, this layer contains a lot of carbon extracted from the atmosphere through photosynthesis.

The research group headed by researcher Minna Väliranta from the University of Helsinki has given the name ‘proto-peat’ to such organic soil accumulations, which are composed mostly of moss formed in increasingly warm arctic climate conditions.

“It’s not yet peat in the actual sense of the word, but you could say it’s the starting point for the formation of peat,” says Väliranta, who works at the Faculty of Biological and Environmental Sciences. The research group also includes Teemu Juselius and Sanna Piilo, doctoral researchers under Väliranta’s supervision.

Such proto-peat deposits elicit interest also internationally. Väliranta is involved in a larger project funded by the Natural Environment Research Council (NERC), a British institution corresponding to the Academy of Finland. This project investigates precisely the same phenomenon, that is, whether global warming has already led to the spread of peatland vegetation into the Arctic. This spread of vegetation is part of a more extensive phenomenon known as ‘arctic greening’, which commonly refers to increasing shrub growth in the Arctic, as vascular plants spread to regions previously barren.

“If this process that generates proto-peat occurs extensively, an unexpected carbon reservoir, or a plant community that mitigates climate change, may be in the process of establishing itself in the north. This reservoir has not been included in the modelling of ecosystems and the atmosphere, as it has traditionally been thought that no new peatlands are formed,” Väliranta notes.

Climate–ecosystem models are continually evolving, and only recently have attempts been made to include the impact of peatlands in such models.

“You can say that the discovery of new carbon sinks brings into play a new component that must be considered in models to better predict the functioning of ecosystems in a warming climate,” Väliranta says.

原始論文：T. Juselius, V. Ravolainen, H. Zhang, S. Piilo, M. Müller, A. Gallego-Sala, M. Väliranta. Newly initiated carbon stock, organic soil accumulation patterns and main driving factors in the High Arctic Svalbard, Norway. Scientific Reports, 2022; 12 (1) DOI: 10.1038/s41598-022-08652-9

引用自：University of Helsinki. "Are new carbon sinks appearing in the Arctic?."