講演情報
[ACG68-P12]Regional estimation of soil organic matter decomposition in Arctic tundra and boreal forest under future global warming scenarios
*佐々木 乃亜1、串田 圭司1 (1.日本大学)
キーワード：
地球温暖化、北極域、土壌有機物分解、葉面積指数
Global warming is progressing in the Arctic at a rate three to four times faster than the global average. This warming in the Arctic promotes the release of carbon dioxide and methane through the decomposition of soil organic matter (SOM). The objective of this study is to estimate the increase in SOM decomposition across the entire Arctic region between the present and the end of the 21st century under the four warming scenarios (very high, high, medium, and low) outlined in the IPCC AR6. We investigated differences based on continents, climatic zone, and Leaf Area Indices (LAI) under these four scenarios. The target area, referred to in this study as the "Arctic region," encompasses the boreal forests extending from the Arctic Circle, tundra vegetation zones, and snow and ice zones. For temperature data, we used surface air temperature data from the IPCC CMIP6 climate projections, divided into 1° grid sections using monthly average temperatures. SOM decomposition was assumed to be expressed by an exponential function of soil temperature. The relationship between soil temperature and the amount of SOM decomposition was derived from observed data in boreal forests. The baseline period for the present was defined as 2015–2025, and the future period as 2088–2098. For the LAI map, we used MODIS LAI data from July 2020. The total increase for the entire Arctic region in 2093 compared to 2020 is estimated to be 2–13 GtC/year for the very high, high, medium, and low scenarios, respectively. Given that global anthropogenic carbon dioxide emissions in the 2010s were approximately 10 GtC/year, SOM decomposition in the Arctic accompanying warming will further accelerate global warming. The results indicated that the increase in SOM decomposition per unit area was greater in regions with a higher LAI. Specifically, the increase in SOM decomposition per unit area was significant at the southern limit of the Arctic region, which overlaps with the distribution area of Chernozem. However, regarding the total sum for each LAI category, the increase in SOM decomposition was largest at an LAI of 2–3 under all four warming scenarios. This is due to the extensive land area covered by regions with an LAI of 2–3 within the Arctic. It is necessary to closely monitor future changes in ecosystems with an LAI of 2–3 and implement appropriate measures. The rate of increase in SOM decomposition is highest at 40–50°N, where temperatures are high, while the absolute increment is highest at 50–60°N. The rate of increase in SOM decomposition is particularly high in Steppe climates, Marine West Coast climates, Humid Continental climates, and Ice Cap climates.