極端な干ばつがサバンナ植生に長期的変化をもたらすことを解明 (Extreme Droughts Cause Long-term Changes in Savanna Vegetation)

2026-02-03 中国科学院(CAS)

中国科学院西双版納熱帯植物園(XTBG)の研究チームは、極端な干ばつがサバンナ植生に長期的な変化をもたらすことを明らかにした。学術誌『Ecology Letters』に発表された本研究では、中国南西部のサバンナを対象に、2019年の深刻な干ばつ後の影響を2017~2022年の観測データで分析した。その結果、炭素吸収機能は比較的早期に回復した一方、地表の反射率や蒸発散量は4年以上低下したままで、局地的な温暖化を助長する可能性が示された。低木は約半減し、耐乾性の高い樹木が優占するなど、植生構造の変化が水循環やエネルギー収支に長期影響を与えることが分かり、気候モデルや保全計画では炭素以外の長期的影響も考慮する重要性が示唆された。

極端な干ばつがサバンナ植生に長期的変化をもたらすことを解明 (Extreme Droughts Cause Long-term Changes in Savanna Vegetation)
An eddy covariance flux tower site in the hot-dry valley savannas of Yunnan. (Image by SONG Qinghai)

<関連情報>

干ばつ後の植生変化は、中国南西部のサバンナ生態系における炭素、水、エネルギーの反応の相違につながる Post-Drought Vegetation Shifts Lead to Divergent Carbon, Water and Energy Responses in a Savanna Ecosystem of Southwest China

Palingamoorthy Gnanamoorthy, Junbin Zhao, Yajun Chen, Linjie Jiao, Boonsiri Sawasdchai, Zhang Jing, Abhishek Chakraborty, Pramit Kumar Deb Burman, Sung-Ching Lee, …
Ecology Letters  Published: 26 January 2026
DOI:https://doi.org/10.1111/ele.70321

ABSTRACT

Increasing drought frequency and intensity affect biophysical functions of natural ecosystems. In tropical semi-arid savannas, while immediate drought effects are well-studied, the drought legacy effects on vegetation composition and associated ecosystem functions remain unclear. We used data of vegetation composition, net ecosystem CO2 exchange, surface albedo and evapotranspiration (ET) in 2017–2022 from a savanna ecosystem, Southwest China, to investigate the legacy effect of an extreme drought event that occurred in 2019. Vegetation declined continuously for 3 post-drought years. While tree numbers declined by 12%, shrub numbers dropped by 50% compared with pre-drought levels, shifting vegetation dominance toward trees. This structural change caused sustained reductions in albedo and ET, which remained below pre-drought levels, despite gross primary production recovering in the years immediately post-drought. Vegetation shifts disproportionately impact ecosystem functions, with energy and water fluxes exhibiting greater vulnerability and potentially enhancing regional warming as droughts increase in Asian savannas.

1900環境一般
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