The biota of Tokyo Imperial Palace grounds, especially of the Fukiage Garden, consists of enriched and distinct flora and fauna found in Tokyo, Japan. An untouched, vast open space in the middle of Tokyo hosts diverse species of wildlife which have been catalogued in field research. For comparison, this article also covers biodiversity in other open spaces in the central districts of Tokyo.
The location of the Tokyo Imperial Palace and its environs
The Tokyo Imperial Palace is situated in the center of Chiyoda-ku, Tokyo. It is in size and encircled by moats. The Palace is divided into the eastern part and the western part by the Kan-Moat and Hasuike Moat. The eastern part is called the Imperial Palace Eastern Garden and has been open to the public since 1968.Biology Study Group[2001:246] In the western part are: the Fukiage Gyoen (Garden), including the Imperial residence, the Palace, and the Imperial Household Agency. An attempt to maintain or recreate its natural state is evident in the Fukiage Garden. The Palace lies on the tip of Musashino Terrace, between the Arakawa River, plus Iruma River and Tama River. There are moats at the northern and western end of the Palace. The height of the Palace is from , with the lowest point being at the Shimo-Dokan Moat.Biology Study Group[2001:246] The eastern end faces the low areas of Tokyo. The Palace is encircled by moats, any of which have been created artificially, since stones had been carried from other places. According to the Meteorological agency neighboring the Palace, the mean temperature is . The difference in mean temperature of summer and winter is about . The precipitation is of considerable degree in summer and autumn, while it is minimum in winter.Biology Research Institute[1989:4]
History of the Palace
Before the Edo Era A midden was excavated from 1955 to 1964. Jōmon pottery was found, indicating that the Palace was inhabited in the Jōmon period, before 300 BCE.Biology Research Institute[1989:4]
Toward the end of the Heian period, Edo Shirō () built his residence in Edo, but its exact location remains unknown. Ōta Dōkan constructed the Edo Castle from 1456 to 1457. Hōjō Ujitsuna occupied the Edo Castle in 1524. Later the Castle was controlled by Hojo's retainers, the Toyama clan.
In 1590, Tokugawa Ieyasu lived here when Edo became his stronghold. The Palace, at that time, faced the sea of Hibiya on the eastern end. The Nishinomaru area had been the site for temples and recreation. There were 16 temples corresponding to the site of Fukiage garden.Biology Research Institute[1989:4–9] In 1603, he became the shōgun and started to enlarge the Edo castle along with many of his successors.
Palace in the Edo Era Many castles and moats were constructed; stones were transferred from Izu Peninsula; A large quantity of lime (material) from Ōme, Tokyo, and the whole Edo castle was completed with the completion of the Outer Moat in 1638.Biology Research Institute[1989:6–9] The Edo castles were greatly damaged in 1657 by the Great Fire of Meireki. (See Fires in Edo) The reconstruction of Tenshu or castle tower was abandoned because of the stability or peace of the times. Fire barrier zones were set up to prevent fires from spreading. That started with moving the primary residences of the Gosanke, who were three major relatives of Tokugawa shogunate; outside of the Edo Castle and dedicating the vacated space to fire prevention. Relocation of residences belonging to other daimyōs and hatamoto, who were direct retainers of the shōgun, followed. From the end of the 17th century to the beginning of the 18th century, the Fukiage Gyoen remained a large garden.Biology Research Institute[1989:6-9]Biology Study Group[2001:248] When Tokugawa Ienobu was in office, (1709–1712) he ordered the daimyōs to help construct a large garden with a large pond (1 hectare which has remained), a fall and a river. During the rule of Tokugawa Yoshimune (1716–1745), the Fukiage gardens changed considerably in accord with his philosophy of the promotion of diligence, industrial development and the encouragement of literary and martial arts. He built a study hall, atelier, astronomical observatory, equestrian grounds, archery field, gun field, herb refinery, food factories for sake, sugar, cake and a sheep-raising yard. However, Tokugawa Ienari (office 1787–1837) made the Fukiage Gyoen to the previous gardens. In the later years of the Edo era, not much attention was given to the garden.
Palace after the Meiji Restoration After the Meiji Restoration, the Gardens were subject to somewhat random change for a century. The Nishinomaru Palace burned down in 1873. A new Meiji Palace was constructed in 1888. Starting in 1928, the government constructed a short golf course, first of 4 courses and in 1931, of 9 holes (par was 30; almost entire garden was used) for the Emperor Hirohito in the Garden.Tashiro[2010:148-151, 215-216] In 1937, Hirohito discontinued golf and the maintenance of lawn was discontinued. Around 1939 and 1941, the maintenance of the garden was also discontinued. A wartime bombproof residence-shelterO-bunko, Biology Research Institute[1989:39] was constructed in 1941. While the formal Meiji Palace burned down, the imperial residence was undamaged. The Fukiage residence was completed in 1961 and the formal Palace was completed in 1968. Starting in 1948, some plants were transplanted in accord with the wish of Hirohito who wanted the Garden to become an old-Tokyo type forest. Basically, the maintenance of the Garden was to be kept at a minimum.
Surveys of the Biota of the Palace
In 1921, the plants in the Palace were inventoried and published in Imperial Palace Landscape.In Japanese language only: Kyujo Fuchi Ko by Yukio Ichikawa This was the first survey of the plants of the Palace. Surveys continued in 1979 (Fukiage Garden), 1980 (Imperial Palace West Block), 1981 (East Gardens), and in 1987-88 (aquatic organisms in moats and ponds). These reports are not available to the public, but provide precise information about the vegetation, its time-course changes, old historic and giant trees. Further surveys started in 1996. The survey of living organisms was reported in 2006.Biology Study Group[20018-9]
Flora
When Tokugawa Ieyasu entered the Edo castle in 1590, there was a beautiful coastline fringed with Japanese black pine trees. The present-day Palace faced the sea at that time. In the early years of the Edo period, there were residences of influential daimyōs. After the latter half of the 17th century, the central parts of the Palace were made beautiful gardens. In the early years of Showa, a golf course of 9 holes was made, which was abolished by the wish of Hirohito in 1937. Hirohito also hoped that the gardens would be left so that nature would be returned; some of the trees were transplanted since 1948.
The biota of the Palace reflects the long history of the Palace. The present Fukiage Garden is mainly composed of woods, although there are small houses, fruit gardens, a rose garden, farms, one for mulberry trees (silkworms). Investigations between 1996 and 1999 revealed woods with broad-leaved evergreen forest trees such as Ilex integra, Castanopsis sieboldii, and Machilus thunbergii on the periphery of the Fukiage Garden, namely over the Dokan Moat, and woods with deciduous broad-leaved trees such as Quercus acutissima in the central part of the Garden. These woods are well cared and minimum cutting is done by the Garden section of the Imperial Household Agency. Although the woods are not the Old-growth forest, the constituents of ever green trees are like those seen in nature. On the contrary, deciduous broad-leaved trees have been planted artificially. The soil is revealed to be good for the development of trees. Well-grown trees and elements of Satoyama such as fruit gardens provide good circumstances for small animals such as insects. Well developed woods of the Palace cool the temperature of Tokyo; the temperature is lower by 2 °C in summer, and are good for the central parts of Tokyo which is influenced by the urban heat island phenomenon.Biology Study Group[2001:211,243]
Giant trees and historic trees In the Fukiage Garden there is a line of Zelkova serrata trees. A tree with a circumference of was revealed to be of genroku era origin (from 1688 to 1703) by the growth ring method in the 1970s. The time might have been earlier since there was a larger tree of . In the Yamabukino Nagare of the Fukiage Gardern, Tokugawa Ienari (office 1787 - 1837) ordered the transplantation of famous 40 black pine trees, which were 17 in the Taisho era and 5 in 1986, including those which were re-transplanted.Biology Research Institute[1989:12-19] In days gone by, several hundred fir trees were seen, but decreased in number and in 2001, there are only 8 trees inside the Garden. In Tokyo Prefecture, Tashiroran (Epipogium roseum), a kind of Orchidaceae without chlorophyll was discovered in the Palace.Biology Study Group[2001:244-245] Between the publication of 1986 and the surveys of 1996-1999, 55 species had disappeared, possibly because of the deepening of the woods and insufficient sunlight.
Bryophytes and lichens There are 77 species of mosses, 29 species of liverworts (hepatics) and one species of hornwort in the Palace. The Palace is the most rich place, followed by Institute for Nature Study with 52 species. Endangered species such as Taxiphyllum alternans (Card.) Z. Iwats and Monosolenium tenerum were found in the Palace, while common species associated with urbanization such as Funaria hygrometrica and Marchantia polymorpha were not found in the Palace.
57 species of lichens were found in the Palace. Of them 3 genera and 5 species were first found in the Palace. Parmotrema tinctorum and Usnea rubescens Stirt which are weak in atmospheric pollution were not found in the Palace.
Algae Interesting algae has been found, including 11 species of cyanobacteria, 156 species of diatoms (including varieties), 58 species of green algae and other species of algae.
Fungi There have been 368 species of fungi found, including 8 new species. Previously Hirohito had inventoried and left in place 64 species of Mycetozoa. New investigations between 1996 and 1999 revealed 88 species of Mycetozoa. 19 species previously recorded were not found in the new investigations.
Naturalist Minakata Kumagusu gave a short seminar to the emperor. He took Hirohito for a walk in the woods on the island, then gave him a 25-minute lecture, on board the royal ship Nagato, on slime molds on June 1, 1929. Minakata presented the Emperor with gifts including 110 specimens of slime molds kept in empty taffy boxes.
Detailed explanations of the vegetation of the Palace Detailed explanations of the vegetation of the Palace with species are made in the reference in English.Biology Research Institute[1989:41–58] They include 1. Trees, Giant Trees and Historic Trees, Bonsai in the Imperial Palace, 2. Herbaceous Plants and Shrubs, Fukiage Gardens, Plants around the Moats, Other locations, Naturalized Plants in Japan 3. Four seasons at the Imperial Palace.
Three noted trees There are three noted species of trees of the Palace. One is a fir tree (Abies) in the Three Palace Sanctuaries. In the Meiji era, other trees of the same species were more than several hundreds in number, but only 8 trees survived in 2001. This one grew to a large size.Biology Study Group[2001:228]