This year, dozens of experts who participated in the "First Symposium on Quaternary Environment and Ancient Tree Research in the Four Cross-Straits and Four Places" visited the "Underground Forest" in Sihui City, Guangdong Province, and collected the specimens of trees buried in various periods for the study of the division. The study of the evolution of the Four Ages provides systematic information. The "underground forest" discovered in recent years is within 20 kilometers of the central city of Sihui. It is only 30 centimeters from the shallowest part of the ground, and 7 meters from the deepest point. The underground is the trunk of the original forest trees. According to Professor Li Pingri of the Guangzhou Institute of Geography, the underground forests of the Sihui are all primitive pine forests, growing in the warm and humid northern tropical zone. It seems that two or three thousand years ago, there was a strong cold current here, and the average annual temperature was below 15 °C. These “underground forests†are concentrated in Sanshui, Sihui, Gaoming and Gaoyao. In the suburbs of Hepu County in the southwest of Guangxi in the 1960s, I saw people dig a similar "underground forest" when repairing the canal. In the pond of the guest house not far from the excavation site, two ancient pines that are tall and straight are more than 20 meters high. The researchers at Hepu Forestry Institute picked the seeds and returned them to the seedlings. The annual seedlings were about one meter high, and the plants were planted in the pond. The “Underground Forest†of Sihui is a rare and precious resource, but the nearby farmers do not understand the scientific value of the ancient trees, and they use rare ancient trees to make low-cost cork for sale. In a large excavation site in a football field, a large pit of 3 meters deep was dug, and there were many old tree roots dug out. There is an electric saw on the top of the pit. Once the roots suitable for making the cork are dug, they are sawed into strips and processed, and each is sold to the purchaser at a penny price. 100 kg of material can produce 300 cork stoppers. Professor Liu Wei, deputy director of the Institute of Earth Environment of the Chinese Academy of Sciences, said that such rare resources as ancient trees are non-renewable, so unscrupulously destroyed, ten hearts are distressing, and called on relevant departments to stop immediately! In the Tertiary, the Pinus genus is not only a wide variety but also widely distributed in the northern hemisphere. After the Quaternary glacial period, Europe, North America, East Asia and Northeast China have been extinct, leaving only one kind of water pine, distributed in China. Southern and southeastern regions. Due to the densely populated and convenient transportation of the Pearl River Delta and the lower reaches of the Minjiang River, the main producing areas are seriously damaged, and the existing plants are scattered. Pinus tabulaeformis is an ancient tree species of plant fossils. It has become a relict plant and remains only in China. It is a precious tree species protected at the national level and is unique in the world. It has important scientific value for the study of phylogeny, ancient plants and Quaternary glacial climate of Firaceae. In 2006, the State Post Bureau issued a set of four special stamps for the "Relic Plants", one of which was a water pine. Its wood material is soft and water resistant, and can be used for construction materials. The roots have a relaxed wooden part with a specific gravity of 0.12 and a large buoyancy. They can be used as lifebuoys and corkware. Fruits and leaves can be used as medicine.
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Pinus tabulaeformis is a semi-evergreen tree with a height of up to 25 meters and a DBH of 120 cm. The bark is brown; the branches are flat, the leaves are drooping, the scales, the diamonds and the lines are curved, and the style is elegant. It is an excellent landscape tree of wetlands and embankments. The flowering period is from February to March, and the cones mature from September to October. The main roots of young trees are developed. After more than 10 years, the main roots stop growing and the lateral roots are developed. The base of the trunk, which is born at the water's edge or in the swamp, is inflated in a column-like shape, and has a knee-shaped respiratory root that exposes the surface of the soil or the surface of the water. If you go to the lakeside of the South China Botanical Garden, you can see this long and tangible water pine. At present, the largest piece of Pinus tabulaeformis in China is more than 70,000 pine forest belts along the Huangyang River in Doumen, Zhuhai City. The area is more than 360 acres. It was planted in the early 1980s and formed a quaint landscape along the river.