Okayama Prefectural Nature Conservation Center
For the purpose of tree planting in this area, three kinds of young evergreen trees, which had been grown in small pots, were planted in 1991: Castanopsis cuspidata var. sieboldii, Quercus glauca and Q. myrsinaefolia. These planted trees were carried by car from their seedbed in the western region far from this area, where many young trees were prepared for transplanting. Many pine trees grew so quickly on the upper slope, however, that the seedlings were left in the understorey because of their slow growth. Therefore this area will succeed to pine forest after several years.
2. Mountain Field
The climate of this area is warm-temperate, with 13.4℃ mean annual temperature and low precipitation of about 1200mm annually. The main vegetation at the research center is pine forest dominated by Pinus densiflora and Pinus thunbergii. Slopes and ridges were covered by pine forest, and valleys were cultivated as paddy fields from ancient times. Now, most of the pine forest in this mountain area is 40 to 50 years old. We could know the age of the forest not only from older people living in the village nearby but also from annual rings of the pine trees that were cut because of pine wilt disease.
Pine wilt disease has spread widely in this area since 1991. We can now recognize that this disease was caused by beetles with symbiotic microscopic organisms. Initially, the pine needles turned brown, just as deciduous trees change their green leaves to brown. Since all the evergreen pine needles changed gradually to brown, it is clear that the pine trees were attacked by the disease. We can see many diseased pine trees on the lower slopes for the first time, spreading gradually to the upper slopes. It has been shown that pine trees over 30 years old would catch this disease more easily than young trees and that the trees die in one or two years after the attack. We cut down the diseased trees to stop the disease from spreading to adjacent areas and also cut the shrubs in the pine forest. As a result, the number of diseased pine trees decreased. In other places adjacent to this research center, many forests changed to deciduous oak forest (such as Quercus serrata). However we think that we should have kept the pine forest in this area as it was before. Therefore we are going to study the succession of this forest in order to know what to do to keep the pine forest in the future.
3. Center complex (Information Regarding Nature Watching is Available Here)
In this exhibition center there is much information regarding nature watching. We hope that many people will take an interest in plants, animals, and insects, etc., and come in touch with nature. We hope that if all people will view many parts of the exhibition with pure interest, they will find nature both surprising and wonderful.
The exhibition has many parts, including a geographical model of the research center; photos on seasonal living things in this area; a theater screening about food chains; a spherical theater imitating the globe that displays images about many global environmental problems such as air pollution, global warming, acid rain, and so on; and an information spot showing the distribution of animals by computer.
4. 'Tancho' Crane Care Center (One of the main facilities at the center is a refuge for the protection and breeding of Tancho cranes)
'Tancho' (Japanese crane) is a kind of bird which was identified as requiring international protection because its worldwide distribution is very limited. Its scientific name is Grus japonensis Muller. Only 26 individuals are now breeding. When the research center started in 1991, the number was only 9. After that time, new birds were born and others came from some zoos in Japan. Some even went to other countries. Some new birds in this center were born under human care. Breeders teach them how to walk and to catch meat. When breeders taught them how to fly, as man cannot fly, the young birds flew into the air and left their keepers behind. The birds eat many fish, shrimp and much grain. Three breeders care for those birds and give them meat twice a day.
5. Marshland Garden (Various plants that grow only in marshes bloom here, thanks to ingenious control of the amount of water and nutrients)
This marshland garden was created 9 years previously by artificial transplantation from other, natural marshlands. Originally this area had been used as paddy fields by the people living in the neighborhood. We reconstructed this area to be suitable for hygrophytes by flattening the ground and burying leather sheets 50cm below the surface to keep the ground wet. We dug a well to get enough low-nutrient water.
Configuration of the ground in this marshland is V-shaped. The western part is 0.5ha wide and has a narrow catchment area, so we decided to make a nutrient-poor marshland imitating the natural marshland in the southern part of Okayama Prefecture. In western Japan there are some nutrient-poor marshlands supporting small plants such as Drosera, Habenaria,Rhynchospora and Eriocaulon because flowing water does not have sufficient nutrients, especially in less wet areas. On the other hand, the eastern part is 0.3ha wide and has a wider catchment area, so we decided to make a marshland garden more nutrient-rich than in the western part.
We got data on the result in the 3rd, 5th, 7th and 9th years since 1991. Comparing these samples with those from the original marshlands confirmed that, until the 5th year, three types of Rhynchospora, perennial plants which form the main component of marshlands, had not taken root sufficiently. In contrast, two types of Eriocaulon, annual plants which are also main components of marshlands, increased widely, as well as other annual plants which are not normally considered to be components. However in the 7th year after transplantation, climbing plants and woody plants growing in the adjacent forest invaded a part of the marshland garden. It was shown that unless suitable management is done, such as removing unnecessary plants, the marshland garden would gradually become drier and succeed to forest.
6. Pine Forest
We will walk into the forest area dominated mainly by pine and oak trees. The main plants growing in the shrub layer are Eurya japonica, Rhododendron reticulatum, Acer crataegifolium and Clethra barbinervis. About 40 years ago when all trees were cut in this area, pine trees were used for constructing houses, scaffolding, and so on. Shrubs were utilized as fuel for cooking, taking a bath and keeping rooms warm, etc. The forest began to succeed from the time when fossil fuel replaced trees. As the pine forest was released from human control, all trees grew naturally. Competition has occurred in the forest. Some pine trees died because of unnatural growth, and others died suddenly because of pine wilt disease. As a result, deciduous oak forest took the place of the pines, and on the forest floor there are now evergreen oaks, such as Quercus glauca, which will be a dominant species in the future.
7. Field for Reconstructing Paddy Fields and its Surrounding Area
This area was originally used as a paddy field controlled by people. The forest surrounding this paddy field was used for collecting fallen leaves and branches of trees, as fertilizer and fuel. A small fire happened in 1989 and the pine wilt disease has spread from 1991. We disposed of all fallen trees and branches in the forest with the assistance of many older people living in this town, who knew very well how to dispose of them. Since then they have helped every year to dispose of all fallen trees and branches in the forest and to mow the field. After gathered matter is piled up and left to make compost, we will use it in a paddy field to grow rice plants.