A Brief History of Vegetation in Hakone
Fossa Magna and Vegetation
The volcanic Mt. Hakone is located on the Pacific Ring of Fire in the center of the Japanese archipelago. It is also the location of the geotectonic belt that geologically divides Japan into east and west formed more than 20 million years ago. It was named the Fossa Magna by Naumann, a German geologist. The west side of the belt is clearly marked by a line connecting Itoigawa city and Shizuoka city, but the east side is covered in volcanic ash. The details are not known. This is the so-called Fossa Magna, a new landform created by volcanic eruptions that started in the middle of the Tertiary period and resulted in rapid sedimentation over a short period of time.
The unique distribution of plants in the Fuji, Hakone, and Izu regions have attracted much attention. Many plants species-specific to the area are not found further west of these regions: the mamezakura (cherry), Hakoneran (orchid), Hakonekometsutuji (azalea), matsunohamannengusa (a Stonecrop family; Sedum hakonense), and the Tateyamagiku (Aster dimorphophyllus), for instance.
When observing the flora of Hakone, it is important to note not only the distribution of plants according to climate but equally their relationship to the geological history of the area.
Let’s take an overall look at the location of Japan’s botanical zones and that of Hakone. The Japanese archipelago follows the eastern edge of the Asian continent over a distance of 3,000 km from Okinawa to Hokkaido. Plant species range from subtropical in the south to subarctic in the north, indicating a wide range of plant distribution. The subarctic plants seen in the Kuril Islands—Kamchatka and Sakhalin in the north, go southward and mostly cover coniferous forest belts and high mountains. These can be found at heights of 1,500 meters or above, in mid-Honshu island. Moreover, one finds the temperate deciduous broad-leaved forest zone, composed of plant-species from China and Korea, which are thought to have spread from the Asian continent, represented by beech. However, the subtropical evergreen broadleaf forest zone of Japanese cypress, Japanese laurel, and oak spread northward from the southwestern part of the country. These species cover the coast and low mountains and extend further northward to the southern part of the Tohoku region.
Evergreen Forests —up to 800 meters
Hakone is a three-layer stratovolcano with a complex topography that has been formed by three eruptions and two volcanic-depression. The highest peak, Mt. Kamiyama, is but 1,438 meters high, therefore, plant distribution does not include coniferous forests. Hakone is covered with evergreen broadleaf forest (Japanese camellia area) up to 750-800 meters, and one finds above that a deciduous broad-leaved forest (beech area).
Hakone is located at the base of the Izu Peninsula, with its foothills straddling Sagami and Suruga Bays, which extend in part to the sea. The area is covered by primary forests of beech and laurel, as well as secondary forests of camphor and black pine.
Today, several regions have been developed and urbanized. Mandarin orange cultivation and camphor and cypress plantations are in evidence. As a result, there is a sparsity of natural forests. On the Manazuru Peninsula, there are some pristine Japanese cypress forests to be found, as well as at Sounji Temple in Hakone-Yumoto, and Amida Temple in Tonosawa. The Sounji Temple, in particular, is designated as a protected habitat for the himeharuzemi (Euterpnosia chibensis) a sort of Cicada which thrives in warm climates.
At slightly higher altitudes, the vegetation mostly consists of oak trees. In general, oak forests are variously distributed depending on topography and soil conditions. Forests mostly covered by the Japanese willow leaf oak tend to be located along ravines, other forests, which are covered by the Japanese blue oak, tend to be located on colluvial soil. On gentle slopes where the soil is firm and stable, forests of bamboo-leaved oak thrive. From the outside to the middle of the ancient outer rim of Hakone, there are many such forest areas. The landscape seen from the national highway along the Hayakawa ravine from Tanosawa to Miyagino is covered with forests of Japanese willow leaf oak. Higher up, near the foot of Mt. Kozuka, there is a secondary forest of Chonowski’s hornbeam, which adjoins the Japanese beech forest area.
In the Sukumo River Valley, one finds a forest dominated by Japanese momi fir in the upper parts of Hatajuku, while on the other hand, the higher part of the valley is bordered by an area of beech forest. Near the river basins, fusazakura(Euptelea), and tamaajisai (hydrangea; Hydrangea involucrata) are found in lined patterns. The light purple tamaajisai flowers bloom in early summer.
In general, forests of Japanese momi fir and forests of southern Japanese Tsuga-sieboldii conifer can be seen at the point of transition from warm-temperate forest to temperate forest in central Honshu. However, no forests of momi fir are observed, with the exception of the Sukumogawa Valley, for its basic composition is of dried colluvial soil. The utmost line of beech forest continues to Mt.Taikanzan.
Deciduous Broad-leaved Forest Area
Throughout the four seasons, broad-leaved forests add color to the diverse beauty of nature. Between winter’s fallen leaves and the green leaves in summer, one finds the flowers of spring, then comes the red leaves of fall. Each season makes a veritable feast for the eye.
In Hakone, these forests are located over the height of Mt. Kozuka and Kami-Gora, the altitude being some 800 meters, with average annual temperatures under 12~13 ℃. Most of the majority of natural forests in Hakone fall into this category.
In Hakone and throughout Japan, temperate beech forests usually consist of broad-leaved deciduous trees. Many plants also thrive on the forest floor. Unfortunately, forests are being denuded by tree-felling in a number of localities. On that account, there have been rising calls for conservation. During the Pacific War, the military were responsible for a further reduction in the total number of trees. Then after the war, much wood was used as fuel for charcoal-powered vehicles. However, in Mt. Kamiyama, Mt. Taigatake, Mt. Kintoki, and Mt. Marudake, beech forests still exist in large swathes. The beech forests of Hakone are part of the bamboo grass beech plant community (Sapio japonica-Fagetum crenatae), which is found in an extensive area on the Pacific side of Japan, and are also found at high elevations of the beech habitat. Tall and semi-tall trees may be found here together with the existing beech. For instance, one finds the Japanese flowering dogwood, Japanese maple, painted maple, tall stewartia, while the shrub layer includes tannasawafutagi, Aburachan(Lindera praecox), yamatsutsuji(Rhododendron kaempferi), and kuromoji (spicebush).
In recent years, beech forests in Hakone have begun to decline, and in their place, tall stewartia secondary forests have started to overtake them; prompting further calls for conservation.
In forests where beech has been in decline, Japanese cedar and mountain ash tend to proliferate, although to less advantage than the bamboo grass beech Sapio japonica-Fagetum crenatae. The above mentioned trees are conjoined with Japanese andromeda and Japanese clethra, plant species often found in Mt. Kintoki and Mt. Marudake. However, the blossoming of the yamaboshi (kousa dogwood) in early summer, and the beauty of the red leaves in fall, provide delightful scenery for visitors and are unique to Hakone.
Asebi-Japanese andromeda and Ryobu-Japanese clethra Plant Colony
This plant colony thrives on the peripheries of sulfurous fields in the Japanese beech forest area. It is composed of semi-tall trees and shrubs, largely dominated by asebi (Japanese andromeda), ryobi (Japanese clethra), and noriutsugi (Hydrangea paniculata Siebold). Indeed, many azalea species such as Japanese azalea (Rhododendron wadanum), sarasadodan(redvein enkianthus), and sunoki(vaccinium) also thrive, however, the varieties of species are sparse.
Furthermore, near to solfataras, plants that are resistant to the direct effects of sulfurous air (in Hakone—mainly hydrogen sulfide), which is normally harmful to most living things, manage to thrive under this condition. In fact, the strong acidity of the soil creates a buoyant ecosystem resistant to the hostile environment.
At the edge of the forest, plants such as himenogariyasu and susuki (miscanthus) form a unique peripheral ecosystem in the sulfur wasteland, including Iougoke (rangiferina) and kotanuki-ran (Carex doenitzli).
Himenogariyasu Yashabushi (Alnus firma) plant colony
The nearer to the solfatara, the more unfavorable conditions become for growing plants. In consequence, the number of plants are limited in number. The pH of the soil is between 3.0 and 2.5, and there is an apparent scarcity of nutrients. The area of erosion is colonized by Alnus firma plants found close to the Owakudani Nature Trail. In Hakone, there are three solfatara—Owakudani, Sounzan and Yunohana. These plants can be found in all three.
Even nearer to the solfatara, a clear line of demarcation can be observed between colonies of himenogarias–miscanthus, and rangiferina–miscanthus in denuded areas, indicating that they are in a marginal state.
In Hakone, plants that are more evolved do not grow in highly acidic areas with pH levels of 2.5 or lower. Furthermore, the sulfurous air and high soil temperature in certain areas affect plants in adverse ways, making them suitable places in which to observe the interaction between the plant and environment.
Wind-beaten Plant Colony
Hakone is affected by strong winds from the southwest for two-thirds of the year. Only plants low in height can survive. These are mainly found on the west side of Hakone and upper slopes of the mountains. The summit of Mt. Kamiyama has beech trees that just reach shrub height. On the other hand, Mt. Komagatake is covered with miyamasuzutake bamboo and tokugawazasa bamboo grass. On the east side, one can see forests of thriving tall trees, shielded from the wind. Mt. Komagatake, Mt. Futago, and Mt. Kintoki, consisting of rocky terrain covered in thin layers of soil, are suited to the onoeranorchid and Hakonekometsutsuji (Tsusiophyllum tanakae) azalea plant colony.
The Hakonekometsutsuji azalea is distributed from Mikurajima Island in the Izu Archipelago to the Chichibu massif, and marks a representative feature of the Fossa Magna. It forms ground cover that clings to rocky areas where other plants cannot grow due to strong winds.
These possibly remind one of the pioneers of cliff vegetation that support colonies of kinreika (Patrinia triloba var. palmata), Hakonehanahirinoki (Leucithoe grayana var. venosa), urahagusa (Japanese forest grass; Hakonechloa macra) and nogi-ran (Metanarthecium). Unfortunately, in recent years, the number of Hakonekometsutsuji has drastically fallen on account ofillegal harvesting. For indeed, they are perfect specimens for Bonsai enthusiasts. Kanagawa prefecture and Hakone-town have designated the area as natural monuments at the summit of Mt. Futagoyama, where the colony grows, and are intent on conserving their posterity.
Marshland Plant Colony
Hakone takes the form of a three-layer stratovolcano, having grasslands and marshlands thriving on its crater plains. In precious times, Sengokuhara was dotted with vast marshlands, around which wet forests had formed. But in later years, much of this terrain has been flattened and turned into golf courses. Sengokuhara is the last surviving marshland in the area. This same marshland was sculpted by the spring water flowing from the northern foothills of Mt. Daigatake, and is home to a variety of mosses and other plants, including oomizugoke(Sphagnum palustre), kasasuge(Carex displata), reeds, sawagikyo (Lobelia sessilifolia), nohanashobu (Japanese iris; Iris ensata), chigozasa (Isachne globosa), misugiboshi (Hosta-plantain lily), sawashirogiku (Aster rugulosus Maxim.), ma-azami (Cirsium sieboldii Miq.), round-leaved sundew-mosengoke (Drosera rotundifolia), and many others.
In 1934, a part of this area (0.7 hectares) was designated as a National Natural Monument, and has been protected ever since. Whilst, the only marshland in Kanagawa, it is also categorized as an intermediary between low marshlands (mainly reeds), and high marshlands (mainly moss), in terms of its diverse species. Much care should be exercised to maintain it for posterity. Hakone Ashinoyu area once had a large colony of mosses, most of which had unfortunately been destroyed over time. Moreover, most of the Japanese alder forests that used to formerly cover large areas in Sengokuhara are nowhere to be found. If only this precious asset of Hakone could have been preserved for all time.
The Nature of Vegetation
When observing the growth of plants, one should consider that their natural state (ecosystem) changes, depending on the location.Natural forests consist of a canopy layer, understory layer, and forest floor, home to shrubs, herbs, and moss all coexisting to create a sustainable ecosystem which supports a variety of living things including animals.
And in the case of asebi (Pieris japonica)–ryobu(Clethra) forest, and itosuge (Carex fernaldiana)–ryobu(Clethra) forest, consisting mainly of shrubs, the matter is somewhat different. With a lack of a canopy layer and an abundant presence of shrubs, the forest floor becomes dark, and fewer varieties of flora flourish. However, in the windy grasslands, trees mainly consist of shrubs, for instance, the Hakonekometsutsuji (Rhododendron tsusiophyllum) and Hakonehanahiri (Leucothoe grayana), and ryobu (Clethra) that thrive on rock faces, supporting the likes of Fuji-aka-shoma(Astilbe thunbergii var.fujisanensis), nogiran(Metanarthecium), onoeran(Galearis fauriei), and Japanese forest grass—urahagusa (Hakonechloa macra).
Plants Which Take the Name of “Hakone”.
One of Hakone’s most attractive features is seen in its wide variety of plant species. Many plants that grow in the region take the name “Hakone” in Japanese, and this makes it more enjoyable when exploring the natural surroundings.