Why is the dawn redwood a precious relict tree species?

Scientific name: Metasequoia glyptostroboides

Family and genus: Taxodiaceae, Metasequoia genus

A deciduous tree, a precious relict plant of our country. The dawn redwood has the advantages of rapid growth, strong adaptability, a straight trunk, and few pests and diseases. The wood is relatively light and easy to work, but its strength is weak and it is not decay-resistant; it is used as timber for construction, furniture, papermaking, and so on. The dawn redwood is highly cold-resistant and requires moist soil; it can grow on lightly saline-alkaline land. It is huge and upright, with luxuriant branches and leaves and changeable leaf color, suitable for concentrated block afforestation or clump planting, and is also an excellent tree species for greening around the four sides and in courtyards.

Seed: Flowers unisexual, monoecious. Male flowers form relatively late; because flowering periods do not overlap, there are many empty seeds. It flowers in February-March, and the cones mature in October-November; when mature, the cones are yellow-brown or dark brown. The thousand-seed weight is about 1.75-2.28 grams, with 440000-580000 seeds per kilogram; because the proportion of seedless seeds is relatively large, the germination rate is only 5-11%. Store seeds dry; germination capacity lasts one year.

Raising seedlings: The seeds are very small and the seedlings are tender and weak, intolerant of drought and afraid of waterlogging, so the nursery site should be chosen as flat terrain with convenient drainage and loose sandy loam. In spring, broadcast sowing or drilling (row spacing 25 cm) is used, with a sowing rate of about 1 kilogram per mu. The seeds are rather small and winged, so they should be sown when there is no wind, mixed with sand or fine soil. After sowing, cover with fine soil, with the thickness just enough to hide the seeds, press lightly, and cover with grass. It is suitable to sow in early spring when the soil temperature is above 12 degrees; after sowing, they germinate in 10 days, begin to emerge in 15 days, and emerge completely in 20 days. In the early stage, the seedlings grow slowly and do not root deeply, so in addition to frequent watering, appropriate shading is needed to avoid sunburn. One-year-old seedlings are 40-70 cm tall, and some can reach more than 100 cm. When seeds are relatively scarce, hardwood or softwood cuttings can also be used for propagation. If the cuttings come from 1-2-year-old young trees, the survival rate is high; as the tree age increases, the survival rate decreases accordingly.