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Oze NP, Gunma
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Before conservation was widely understood, hikers spread picnic sheets and even played badminton on Ayamedaira. By the mid-1960s, trampling had left about 1.2 hectares bare—the largest such scar in Oze—and boardwalk construction began in 1964.
When the Nikkō-kisuge flowers have finished, Kinkōka takes the stage: its little star-shaped yellow blooms open upward along each stem, usually peaking in late July. In autumn, the same plant’s leaves turn bright orange.
A popular explanation says Ayamedaira was named for Kinkōka leaves mistaken for iris leaves. But a Gunma natural-history report’s author recalled blooming Hiōgi-ayame around its ponds in the 1960s, and argued the name may refer to real irises.
Retired boardwalk planks were reused as barriers to hold Ayamedaira’s peat in place. But solid boards trapped water and caused seeds to rot, so restoration workers switched to larch panels with drainage holes—a small design change with a big job.
By 2008, restoration had greened about 90% of the bare area, though some ground remained difficult to recover. Later trials paired native seeds with sphagnum moss; successful plots gained plant cover and species within about 3–4 years.
Ayamedaira’s peat is about 1–1.2 metres thick. Using a volcanic-ash layer from the mid-6th century as a time marker, researchers estimated that later peat accumulated at just 0.23 millimetres a year—a remarkably slow-built sponge beneath the boardwalk.
