Â Â The southwestern birch is the southernmost species of birch in the northern hemisphere. It is concentrated in the southwestern, southern, southeastern and western Guangxi, southwestern, northwestern and southern Guizhou regions. These distribution areas are connected with the distribution areas of Vietnam, Laos and Myanmar, forming the central distribution area of â€‹â€‹southwestern birch. The horizontal distribution range is approximately 97 Â° 3 â€²â€² to 108 Â° E, 19 to 25 Â° N , and is vertically distributed at an altitude of 200 to 2800 m.
Morphological characteristics: The maturity of southwestern birch seeds varies from place to place. Yunnan and Guangxi are generally from January to March , and Hainan Island is from April . The seed maturity period is short, and the seed is usually scattered for about 10 days, so the seed collection should be timely. When the ear turns from cyan to yellowish brown, it is mature. The seeds should be cut together with the ears. After 3-5 days of dryness, the seeds will automatically fall off the ears, obtain clean seeds, and store them in the refrigerator for removal.
The growth of the southwestern birch seedlings should pay attention to the management of water and fertilizer, especially the management of water. The water in the seedling stage should not be too much, and it should not be short of water. If the soil surface is white, it should be watered. Otherwise, it will be difficult to resume growth and death after the seedlings dry up. The humidity is moistened with nutrient soil, and it is important to avoid excessive watering to cause rotten seedlings. This is an important measure that needs special attention and emphasis.
Biological characteristics: Betula platyphylla is a strong positive tree species, hi-light, not shade-tolerant, suitable for acid soil, not strict on soil fertility, and has certain tolerance to barrenness. It grows fast and yields high in the deep, loose and well-drained mountain soils south of 25 Â° north latitude . According to the Tropical Forestry Experiment Center , the average height of 18 years is 18m , the average breast diameter is 21.5cm , and the dominant wooden diameter and tree diameter. height were 32.6cm and 24.0m. A plantation forest was built in 2001 by the Yongkeng Forestry Group of our province , and was surveyed in May 2003. The average height is 5.9m and the average breast diameter is 6.4cm . The growth can be compared with the local eucalyptus forest. Also afforestation in hilly areas, but should be more than 200m above sea level woodland, planting area less than 200m of "sunburn" that burns stems phenomenon occurs, affecting their growth and development even lead to death. The growth of Betula platyphylla is rapid, and it is another excellent fast-growing precious tree species after eucalyptus. It is mixed with negative or neutral shade tree species, such as red needle, wood lotus, fragrant incense, eucalyptus, fir and many other coniferous and broad-leaved species. Wide, wide-broad mixed forest, not only grows well, but also has good forest structure, strong protective performance and good ecological effect.
Economic value: The southwest birch wood is not warped or cracked, the shrinkage ratio is small, it is not easy to be deformed, and the pattern and color are beautiful. In addition to traditional furniture, construction and military applications, it is commonly used as plywood, high-grade furniture, wood flooring and interior decoration materials. Its resonance performance is good, and it is also an excellent instrument material. The bark contains 6.9 to 11.6% of tannins and can be extracted from tannins .
Southwest birch wood wider use of high economic value, timber prices continue to rise, 1980s 600-700 yuan / cubic meter, 1990s 1000-1400 yuan / cubic meter, currently more than 2,000 yuan / cubic meter. The results of natural forest survey show that the 30- year-old breast diameter is 35cm , the tree height is about 25m , and the accumulation is 54.12 cubic meters / mu, ( 811.78 cubic meters / ha), which can produce 568.25 cubic meters / ha of wood, with an output value of 75760 yuan / mu, ( 1136400 yuan). / hectare), the average annual output value is 56,820 yuan / hectare.
Wood traits: deciduous trees. The bark is brown to reddish brown, and the paper is transversely peeled off. The wood is reddish brown to taupe, the difference between the heart and the sapwood is not obvious, the growth wheel is slightly obvious or obvious, and the wheel boundary is thin. The tube hole is slightly less, slightly smaller to medium, and evenly distributed (discrete material). Axial parenchyma was not seen. The wood ray is as low as medium; it is very fine to slightly fine, and it is clear under the magnifying glass; there are very fine ray spots on the radial section. The texture is straight, the structure is fine, uniform, and the hard weight is medium.
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