Japan is one of the most densely forested countries on Earth (Kevin Short)
Un bois sacré au Japon. Source: greenshinto.com link
Kevin Short / Daily Yomiuri Columnist
Japan is certainly a land of trees and forests. Even today, 68.5 percent of the national land is covered with forest. This figure is third behind Finland (72.9 percent) and Sweden (68.7 percent), and over twice the world average of 31 percent. An estimated 1,000 species of woody plants live in Japanese forests, which is about the same as the figure for all of North America.
One reason for the amazing diversity of Japanese trees can be found in geologic history. The Japanese islands were almost completely free of ice during the last glacial period. In contrast, until 10,000 years ago much of northern and western Europe was covered by glaciers up to a kilometer thick.
Geographical conditions also help support sylvan biodiversity. With warm oceans currents flowing on both sides, the Japanese archipelago is blessed with a mild, wet climate that is ideal for tree growth and forest development. In addition, the islands stretch a long way in the north-south direction, and climatic zones range from subtropical in the Ryukyu Islands to subarctic in parts of Hokkaido.
Botanists understand and document plant diversity using a formal taxonomic system. Trees are first divided into two major groups, gymnosperms and angiosperms, based on the type of flower and fruit. Gymnosperms include all the trees we normally call conifers, and angiosperms the ones we think of as broad-leaves. Some trees, such as the ginkgo, however, have wide leaves but are actually gymnosperms.
The vast majority of Japan's native tree species are broad-leaves, and most of the nation's natural forests are dominated by broad-leaves. The general idea is that angiosperms, which sport a more advanced flower structure, enjoy a competitive advantage over gymnosperms. All else being equal, angiosperms will thus tend to monopolize favorable environments, leaving the gymnosperms to get by in marginal habitats such as deeply shaded valleys and exposed ridges.
But today, as anyone traveling around Japan can verify at a glance, the hills and lower mountainsides in most areas of the country are totally dominated by conifers. In fact, a full 40 percent of the nation's forests are pure stands of conifers. These are not natural forests at all, but commercial timber plantations.
Major Japanese timber trees include sugi cryptomeria (Cryptomeria japonica), hinoki cypress (Chamaecyparis obtusa), sawara cypress (C. pisifera) and karamatsu larch (Laris leptolepis). Of these, the cryptomeria is by far and away the most commonly planted. This is an endemic Japanese species, distributed from northern Honshu south to Yakushima Island in Kagoshima Prefecture. Typical natural habitat is in deep muddy soils near the bottom of steep ravines, especially on shaded north-facing slopes.
Sugi is a close relative of the coast redwoods and giant sequoias of California. Although not quite as tall and fat as these behemoths, large specimens can live for over 1,000 years, and reach heights of up to 50 meters. In crowded woods, the trees grow straight and true. The Japanese name sugi is thought to be derived from massugu-ki, or "perfectly straight tree."
The aromatic wood of the cryptomeria is soft and easily worked, perfect for cutting into the straight boards and columns used in building. The Japanese have prized this tree highly since ancient times. According to classic mythology, the great kami deity Susano created the first sugi by plucking hairs from his beard and scattering them over the islands.
Sugi is what botanists call a monoecious species. This means that the male and female flowers bloom separately, but each individual tree has both types. The light brown conelike male flowers occur in clusters at the tips of some branches. When daytime temperatures begin climbing up into the mid-teens, these cones split open to release their loads of miniscule feather-light pollen grains.
The inconspicuous female flowers form at the tips of separate branches. When pollinated these structures develop into spiky cones that ripen and release their seeds in late autumn and early winter. The sugi flowers rely solely on the wind to carry their pollen from tree to tree. The pollen grains are produced in mind-boggling quantities, and are able to float for dozens or even hundreds of kilometers on the spring breezes.
As noted earlier, single-species commercial conifer plantations account for 40 percent of the total forested area nationwide. In many prefectures, however, this figure is well over 60 percent; it's even higher on hills and lower mountainsides surrounding the major cities. In late February and early March, immense clouds of yellow-green sugi pollen dust float down onto the urban areas, like some amorphous monster out of a kaiju science fiction movie. The number of people suffering from sugi pollen allergy is estimated at over 20 million.
Most of these sugi plantations were established in the years following the Pacific War, when demand for lumber for rebuilding the destroyed towns and cities was high. Entire hillsides and even watersheds were stripped bare of their diverse natural broad-leaved forests, and completely replanted in tight rows of sugi. Several decades later, however, tariff reductions made cheap imported lumber products widely available, and the price of sugi wood dropped dramatically. As a result, many plantations have since been abandoned as commercially unworkable.
Cryptomeria is a truly magnificent tree, and properly thinned and managed sugi plantations form a valuable wildlife habitat of their own. The sheer extent of the plantations, however, has placed Japan's magnificent natural broad-leaved trees and forest ecosystems in grave danger of extinction.
Short is a naturalist and cultural anthropology professor at Tokyo University of Information Sciences.
(Feb. 28, 2013)
Un Ginkgo biloba sacré. Source: greenshinto.com link
Les arbres sacrés sont nommés shimboku au Japon. Ils abritent un esprit, une divinité. Pour les distinguer, on les entoure d'une corde de paille de riz (shimenawa).
Lire à ce sujet le remarquable article: Le bois sacré au Japon link sur le site krapooarboricole.wordpress.com.