The Forests of Okunikko
The diversity of plant life in Okunikko is because of the region’s many microclimates, which are caused by differences in elevation and unusual weather patterns in the area. The elevation difference between Lake Chuzenji and the top of Mt.Shirane is more than 1,300 meters. The Okunikko mountains are roughly along the midline of the island of Honshu, and certain areas are affected by wind and weather patterns from the Pacific Ocean to the east or from the Sea of Japan to the west.
Three Zones
The mountains of Okunikko can be divided into three vegetation zones, ranging from the lowest point at the bottom of the Iroha Slope Roads (900 m) to the highest at the summit of Mt. Nikko Shirane (2,578 m).
Lower Zone: Upper Montane (Broadleaf Deciduous Forest)
The upper montane zone starts at the Iroha Slope Roads, which wind up around Umagaeshi, and includes Senjogahara Marshland and Lake Chuzenji. Its forests consist primarily of broadleaf deciduous trees such as Japanese oak (Quercus mongolica var. crispula), but also contain some evergreens such as Nikko fir (Abies homolepis).
Middle Zone: Subalpine (Evergreen Coniferous Forest)
The subalpine zone begins at about 1,475 meters, the elevation of Lake Yunoko. It is largely covered with evergreen coniferous forests of northern Japanese hemlock (Tsuga diversifolia) and Veitch’s silver-fir (Abies veitchii). There are also some deciduous trees, such as Erman’s birch (Betula ermanii).
Upper Zone: Alpine (Alpine Shrubbery)
The top of Mt. Shirane is an alpine zone, which begins at about 2,400 meters (the elevation of Mt. Mae-Shirane). Above the tree line, the ground is covered with alpine flora, including black crowberries, whitish gentians, and lingonberries.
Giant Trees of Okunikko
Thirty of the largest and most remarkable trees in Okunikko appear on the map and chart on the left. The following five trees are distinctive and easy to access:
[#1] A 250-year-old Japanese elm (Ulmus davidiana var. japonica, 25 m tall) whose branches spread out over Kegon Valley, near Kegon Falls
[#6] A 1,100-year-old Japanese yew (Taxus cuspidata, 23.5 m tall) at Futarasan-Jinja Chugushi Shrine (Natural Monument)
[#13] A 350-year-old Siebold’s beech (Fagus crenata, 26 m tall) along the walkway near the British and Italian Embassy Villa Memorial Parks
[#17] The “king” of the giant trees of Okunikko: a 1,000-year-old Japanese oak (Quercus mongolica var. crispula, 32.5 m tall, 6.8 m in circumference) at Lake Sainoko
[#19] The “Lady of Odashirogahara”: an 80-year-old white birch (Betula platyphylla, 17 m tall) whose lone white trunk is striking against the surrounding scenery