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As grasslands are left untended, controlled burning is being considered a labor-saving strategy to prevent forest encroachment. A research team from Kobe University discovered that this technique leads to enhanced biodiversity and an increased presence of endangered plant species in certain grasslands, influenced by the type of soil they grow in.
For centuries, humans have maintained grasslands through methods like grazing, mowing, and controlled burning, which help stop forests from overtaking these areas. However, grazing and mowing require significant labor, and as rural populations decline, grasslands are disappearing on a global scale. This loss threatens the habitats of various plant and insect species, including many that are endangered, which rely on grassland ecosystems. To preserve these habitats, land managers are exploring “prescribed” burning—what is commonly referred to as controlled burning—as a more efficient alternative. Yet, it is important to note that not all grasslands are the same. According to ecologist Ushimaru Atushi from Kobe University, “Many studies have concentrated on the impacts of different management strategies on plant diversity, but few have examined the effects of soil differences.” As a result, there’s a lack of clarity regarding which type of soils are more suitable for prescribed burning to support high levels of plant diversity, particularly for endangered species.
To address this issue, Ushimaru’s team, led by master’s student Asada Airi, conducted research on Mount Fuji. There, they found a training site for the Japan Self-Defense Forces, where grasslands of varying soil types are managed via prescribed burning each April. “We observed that some areas, particularly those on young lava flows, had a higher concentration of endangered species,” explains Ushimaru, justifying their choice of research location to investigate which soil characteristics affect species abundance. The team established 100 one-square-meter plots across different soil types in the grasslands, cataloging all plant species and measuring a variety of physical and chemical soil factors.
The findings, now published in the journal Plants, People, Planet, reveal that grasslands situated on young lava flows possess a greater overall species richness, native species richness, and a higher frequency of red-listed plant species in comparison to those on both young and old scoria bedrock. Additionally, differences in soil acidity, depth, and rock coverage were identified, helping the team conclude that these factors are crucial for the survival of rare plant species.
Prior research indicated that acidic soils hinder nutrient uptake for plants and that shallow soils tend to favor slower-growing plant species. Asada posits that since prescribed burning revitalizes plant growth in grasslands, these characteristics limit the dominance of fast-growing species, thus providing generally outcompeted and rare species a greater opportunity to thrive.
Ushimaru summarizes, “Our study was able to pinpoint environments where grasslands managed through burning can sustain a noteworthy variety of endangered species.” The team concludes their research with the statement, “Identifying environments conducive to maintaining high plant diversity through prescribed burning is not only crucial for understanding the survival conditions of grassland plants in Japan, but also vital for future efforts in conserving and restoring grassland ecosystems and their associated species.”
This research received funding from the Japan Society for the Promotion of Science (grants 19H03303 and 24K01782) and the Environmental Restoration and Conservation Agency (grant JPMEERF20234005). It was carried out in collaboration with researchers from J. F. Oberlin University.
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