極端な干ばつが草原の安定性を乱し、優勢種の影響を弱める(Extreme Drought Disrupts Grassland Stability, Weakening Dominant Grasses’ Influence)

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2025-05-21 中国科学院(CAS)

中国科学院応用生態研究所の羅文濤博士らの研究チームは、極端な干ばつが草原の生産性とその安定性に与える影響を明らかにしました。長期にわたる降水量66%削減の実験により、通常は生産性の安定に寄与する優占種の影響力が干ばつ下で低下し、種間の非同期的な反応が生態系の変動を緩和する主要な要因となることが判明しました。また、特定の形質組み合わせ、特に高い比葉面積と高密度の組織構造が、干ばつ耐性の安定性を高めることが示されました。この知見は、劣化した草原の修復や干ばつに強い種の選定に役立つ可能性があります。

<関連情報>

極端な干ばつは優勢草を抑制することで草地生産性の時間的変動を増大させる Extreme Drought Increases the Temporal Variability of Grassland Productivity by Suppressing Dominant Grasses

Wentao Luo, Naohiro I. Ishii, Taofeek O. Muraina, Lin Song, Niwu Te, Robert J. Griffin-Nolan, Ingrid J. Slette, Samuel R. P. J. Ross, Takehiro Sasaki, Jennifer A. Rudgers …
Ecology Letters  Published: 28 April 2025
DOI:https://doi.org/10.1111/ele.70127

ABSTRACT

Extreme droughts are intensifying, yet their impact on temporal variability of grassland functioning and its drivers remains poorly understood. We imposed a 6-year extreme drought in two semiarid grasslands to explore how drought influences the temporal variability of ANPP and identify potential stabilising mechanisms. Drought decreased ANPP while increasing its temporal variability across grasslands. In the absence of drought, ANPP variability was strongly driven by the dominant plant species (i.e., mass-ratio effects), as captured by community-weighted traits and species stability. However, drought decreased the dominance of perennial grasses, providing opportunities for subordinate species to alter the stability of productivity through compensatory dynamics. Specifically, under drought, species asynchrony emerged as a more important correlate of ANPP variability than community-weighted traits or species stability. Our findings suggest that in grasslands, prolonged, extreme droughts may decrease the relative contribution of mass-ratio effects versus compensatory dynamics to productivity stability by reducing the influence of dominant species.

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