2024-12-18 カリフォルニア大学リバーサイド校(UCR)
カリフォルニア大学リバーサイド校(UCR)の研究者たちは、侵入性の外来種である枯れた草(サッチ)が積み重なり、在来の野生植物の発芽や成長を妨げていることを発見しました。この問題に対処するため、彼らはサッチを取り除く「レーキング」という手法を試験し、その効果を確認しました。レーキングは、光を地表に届かせ、在来植物が成長する機会を提供します。研究の結果、レーキングにより在来の野生植物の多様性が約5%増加し、侵入性の外来植物も約7%増加しました。この手法は、費用対効果が高く、草原や沿岸のセージスクラブ生態系の回復に向けた第一歩として有望です。
◆レーキングは、侵入性の外来草種であるリップガットブローム(Ripgut brome)などの抑制にも効果的であり、家畜の飼料としての価値を高める可能性があります。しかし、一部の外来野生植物も増加するため、管理者は生態系全体のバランスを考慮しながら適用することが重要です。この研究は、2024年12月18日に『Restoration Ecology』誌に掲載されました。
<関連情報>
- https://news.ucr.edu/articles/2024/12/18/inexpensive-fix-californias-struggling-wildflowers
- https://onlinelibrary.wiley.com/doi/10.1111/rec.14340
アメリカ、南カリフォルニアの海岸沿いのセージ低木に大量に侵入したゴミを除去すると、在来種と外来種の雑草の両方が促進され、植物の多様性が増加する Litter removal increases plant diversity by promoting both native and exotic forbs in heavily invaded coastal sage scrub in Southern California, U.S.A.
Advyth Ramachandran, Caryn D. Iwanaga, Michael Fugate, Jared D. Huxley, Annika Rose-Person, Rhea Amatya, Thuy-Tien Bui, Marko J. Spasojevic
Restoration Ecology Published: 16 December 2024
DOI:https://doi.org/10.1111/rec.14340
Abstract
Litter produced by exotic grasses is known to negatively impact native species through multiple mechanisms. While litter removal is a potential restoration tool to recover native species, the effects of litter removal on overall plant community structure are not well understood as most studies focus on native species recovery. In a litter removal experiment in Southern California, U.S.A., we found that plant communities receiving litter removal treatment differed in species composition from control plots and had 4.4% higher native forb relative abundance and 7.0% higher exotic forb relative abundance, on average. These changes in exotic and native forb abundance with litter removal altered community structure by increasing overall Shannon diversity, while only having a modest positive effect on overall species richness. In contrast, we found no effect of litter removal on the species richness or Shannon diversity of native species. Taken together, these findings suggest that in herbaceous systems litter removal is likely to alter community composition primarily by increasing the abundance of native and exotic forbs already present in the community, rather than by allowing the establishment of new native species. Our study adds to a growing body of literature demonstrating that litter produced by exotic grasses inhibits native forbs in California grasslands and coastal sage scrub and highlights a potential trade-off between controlling exotic grass invaders and controlling exotic forb invaders. If managing for increased species diversity is the goal, litter removal may be an appropriate intervention to move plant communities toward a more diverse state.
Implications for Practice
- In California coastal sage scrub (and likely similar systems such as California annual grasslands), litter removal via raking can be an effective strategy to increase native forb abundance, but also increases exotic forb abundance.
- By promoting the growth of native forbs already present and co-occurring with invasive grasses, litter removal can increase the abundance of native forbs even without seed addition.
- Litter removal can present a trade-off between controlling exotic grass invaders and controlling exotic forb invaders; however, if managing for higher species diversity is the management goal, litter removal may be an appropriate intervention.
