窒素汚染と二酸化炭素の増加： 草原の生物多様性に共同の脅威？(Nitrogen pollution and rising carbon dioxide: A joint threat to grassland biodiversity?)

2024-10-16 ミシガン大学

＜関連情報＞

• https://news.umich.edu/nitrogen-pollution-and-rising-carbon-dioxide-a-joint-threat-to-grassland-biodiversity/
• https://www.nature.com/articles/s41586-024-08066-9

高CO2は24年間にわたり窒素による多様性の損失を減衰させ、その後増幅させる High CO2 dampens then amplifies N-induced diversity loss over 24 years

Peter B. Reich,Neha Mohanbabu,Forest Isbell,Sarah E. Hobbie & Ethan E. Butler
Nature  Published:16 October 2024
DOI:https://doi.org/10.1038/s41586-024-08066-9

Abstract

Rising levels of atmospheric carbon dioxide (CO₂) and nitrogen (N) deposition affect plant communities in numerous ways^{1,2,3,4,5,6,7,8,9,10,11}. Nitrogen deposition causes local biodiversity loss globally^12,13,14, but whether, and if so how, rising CO₂ concentrations amplify or dampen those losses remains unclear and is almost entirely unstudied. We addressed this knowledge gap with an open-air experiment in which 108 grassland plots were grown for 24 years under different CO₂ and N regimes. We initially found that adding N reduced plant species richness less at elevated than at ambient CO₂. Over time, however, this interaction reversed, and elevated CO₂ amplified losses in diversity from enriched N, tripling reductions in species richness from N addition over the last eight years of the study. These interactions resulted from temporal changes in the drivers of diversity, especially light availability, that were in turn driven by CO₂ and N inputs and associated changes in plant biomass. This mechanism is likely to be similar in many grasslands, because additions of the plant resources CO₂ and N are likely to increase the abundance of the dominant species. If rising CO₂ generally exacerbates the widespread negative impacts of N deposition on plant diversity, this bodes poorly for the conservation of grassland biodiversity worldwide.