気候変動下でササ群落はどう変化するか? ――植生動態モデルを用いた、ササ分布・バイオマスの将来予測――

2026-11-10 東京大学

東京大学の研究グループは、動的全球植生モデル(SEIB-DGVM)を改良し、気候変動に伴う北海道のササ類の分布とバイオマスの将来変化を予測した。研究では、ササを大型タイプ(チシマザサ・クマイザサ)と小型タイプ(ミヤコザサ)に分類し、積雪深に対する応答や数十年に一度の一斉開花・枯死をモデルに組み込んだ。現在および将来の気候条件を用いてシミュレーションした結果、現在は北海道の約83%を占める大型ササの分布割合が、2100年頃には約23%まで縮小すると予測された。これは、温暖化による積雪深の減少によって、大型ササが冬季に雪の下で保護されにくくなるためと考えられる。また、ササのタイプが維持される地域では地上部バイオマスが約65%増加する一方、大型から小型に置き換わる地域では約55%減少し、北海道全体では平均約16%減少すると推定された。本研究は、積雪変化が植生構成と生物量に及ぼす影響を定量的に示したものであり、気候変動下の森林生態系の将来予測や森林管理への応用が期待される。

気候変動下でササ群落はどう変化するか? ――植生動態モデルを用いた、ササ分布・バイオマスの将来予測――

図1:現在と将来のササバイオマス(1平方メートルあたり乾燥重量)の分布

<関連情報>

動的全球植生モデルを用いた、日本北部における矮性竹の分布動態とバイオマスの将来予測 Future projections of distribution dynamics and biomass of dwarf bamboos in northern Japan using a dynamic global vegetation model

Ai Obata & Tsutom Hiura

Progress in Earth and Planetary Science  Published:09 November 2026

DOI:https://doi.org/10.1186/s40645-026-00860-5

Abstract

Dwarf bamboo (DB) species are widespread across East Asia, including northern Japan, where they form pure communities and strongly influence ecosystem structure and vegetation dynamics, including tree regeneration. The regional distribution of different DB types is strongly associated with maximum snow depth, which is expected to decrease under future warming. Climate-induced changes in snow conditions may therefore alter both the distribution and biomass of DB vegetation. However, dwarf bamboo and its sensitivity to snow conditions have rarely been represented in vegetation models, such as dynamic global vegetation models, which limits our ability to project the effect and change of DB under climate change. In this study, we developed a dwarf bamboo submodule within the SEIB-DGVM framework to simulate future changes in the distribution and aboveground biomass (AGB) of DB species in Hokkaido, northern Japan. Under the RCP8.5 scenario, our simulations indicate that Sasa nipponica, a smaller species adapted to shallower snow conditions, is likely to expand its distribution. Across three different climate datasets under the RCP8.5 scenario, an average of 72.8% of the grid cells classified as the tall-stature type under the present-day climate were projected to shift to the short-stature type. Simulated AGB responses differed depending on whether the dominant DB type remained stable or shifted between types. Across all grid cells, mean AGB decreased by 403 g DM m⁻2, corresponding to approximately 16.1% decrease relative to the current climate. Our results demonstrate that climate-driven reductions in snow depth can cause substantial shifts in the distribution and biomass of dwarf bamboo. Explicitly representing these snow-mediated vegetation shifts in DGVMs may therefore improve projections of non-tree vegetation dynamics under climate change. The developed model provides a framework for evaluating future changes in dwarf bamboo vegetation and their ecological consequences in northern Japan.

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