What's the difference between Taxodium ascendens and Taxodium ascendens?

There are three kinds of Taxodium distichum, Taxodium distichum, Taxodium distichum. Sushang' Taxodium ascendens is an excellent provenance selected from different geographical provenances and families of Taxodium ascendens. Zhongshan fir 302 is an excellent clone selected from the hybrid of Taxodium ascendens and Taxodium mexicana (in addition, Zhongshan fir 40 1 is a clone selected from the hybrid of Taxodium ascendens and Taxodium mexicana). Taxodium plants are all ancient "relict plant". It flourished from the late Jurassic to the early Cretaceous. In the Miocene and Pliocene of Tertiary, it was still widely distributed in North America and northern Eurasia 20-30 million years ago. Fossils of leaves, cones and seeds of Taxodium ascendens in Mesozoic have been found in the United States, Siberia, Russia, Heilongjiang, Jilin, Songliao Plain and Yunnan. After the Quaternary Glacier, they all became extinct in Eurasia and only survived in parts of North America and Latin America.

In recent 400 ~ 500 years, Taxodium species have been introduced to vast areas far away from its modern natural distribution areas because of their strong adaptability, fast growth, beautiful tree shape, excellent materials and few pests and diseases. Including Europe, Asia, Africa and Australia, as ecological environment and timber afforestation tree species. China was introduced around 1900, and was first planted in Nanjing. At present, there are still several hundred-year-old trees in the campuses of the middle school affiliated to Nanjing Southeast University and Nanjing Normal University, as well as in the gardens of individual residents. The height of the tree is nearly 30m, DBH130cm, and the crown width16m. In Jigongshan Nature Reserve, Henan Province, there is still a 50-year-old budding forest of Taxodium ascendens (the original forest was cut down by the Japanese army in War of Resistance against Japanese Aggression, and then germinated and regenerated), with the maximum tree height of 32 meters and DBH of more than 70 centimeters. After 1970, Taxodium ascendens and Taxodium ascendens were introduced into China as fast-growing and high-yield timber trees. At present, the afforestation area of Jiangsu, Shanghai, Zhejiang, Anhui, Shandong, Henan, Shaanxi, Jiangxi, Hunan, Guangxi, Yunnan, Guizhou, Sichuan, Guangdong, Qiong and other provinces (cities) is nearly 65,438+10,000 hectares. Most of them have become forests and timber. It has brought good ecological, economic and social benefits into play. Chinese experts in forest genetics and breeding have been studying the genetic improvement of three species of Taxodium ascendens and cultivated some new cultivated varieties. 1960, Professor Ye Pei from Nanjing Forestry University crossed Taxodium mexicana ♀ and Cryptomeria fortunei ♂ and obtained a few hybrids. This hybrid is shaped like Taxodium ascendens in Mexico, planted in Jiangsu, Hubei and other places and has grown into a big tree. From 1973 to 1983, researcher Chen Yonghui of Institute of Botany, Nanjing Chinese Academy of Sciences crossed Taxodium ascendens ♀ with Taxodium ascendens ♂ to obtain excellent hybrid clone Zhongshan 302; Hybridization clone Shanshan 40 1 was obtained by crossing Taxodium ascendens ♀ and Taxodium mexicana ♂. Through appraisal, it has been popularized and applied in Jiangsu and surrounding provinces, and it is growing well. After 1990, researcher Wang Qiming of Jiangsu Academy of Forestry Science and others carried out the breeding of different geographical provenances and families of Taxodium ascendens, and selected the excellent provenance of Taxodium ascendens-Susong 1, which has been identified as a new tree species for popularization and application by the State Forestry Administration and Jiangsu Forestry Administration. Jiangsu, Shanghai and other provinces (cities) have begun to be excellent new varieties for ecological environment greening. According to the existing data, the modern natural distribution, tree morphology, biological characteristics and suitable application scope of Sushan 1, Zhongshan, Taxodium ascendens, Taxodium ascendens and Taxodium ascendens were compared and analyzed for reference in selecting and cultivating these tree species.

Where is the modern natural distribution of Taxodium ascendens?

The modern natural distribution areas of Taxodium ascendens and Taxodium ascendens are similar, both of which grow in the eastern and southern parts of the United States, in a wide range of 23 ~ 42 north latitude, from Virginia in the northeast to the southernmost state of Florida *** 18. The climate zone belongs to temperate zone to subtropical zone, with annual extreme low temperature of 20 ~-35℃, annual precipitation of 760 ~ 1630mm and altitude of 0 ~ 150m. It grows in the permanent swamp all the year round, and the tree base is immersed in water for half a year. Therefore, there are few other tree species in the forest, only accompanied by some aquatic plants such as duckweed and purple duckweed. When the water recedes in autumn, only some herbs grow in the forest.

The modern natural distribution of Taxodium ascendens in Mexico is quite different from Taxodium ascendens and Taxodium ascendens. It is distributed in the tropical and subtropical areas from Texas in the southwest of the United States to eastern Mexico and Guatemala in the south, with a latitude of 25 ~ 16. The extremely low temperature plateau with annual temperature above 25℃, annual precipitation1200mm and altitude1400 ~ 2400m cannot grow in the swamp area.

What does it look like-morphological characteristics

These trees are all tall trees. During the period from young to middle age (under 50 years old), Susong 1, Zhongshan, Taxodium ascendens and Taxodium mexicana all have oval crowns with cones or umbrellas, and some plants will gradually form irregular broad crowns over 50 years. Taxodium ascendens has a narrow crown, which is basically in the shape of a steeple under 50 years old.

Dry fir tree species are excellent in material and have the title of "eternal wood" in the United States. Taxodium ascendens, Susong 1 and Taxodium ascendens have obvious trunks, are completely straight, and do not branch from the base to the top of the trunk, so the yield is high. Irregular plate roots are formed on the dry foundation of low-lying areas and wetland areas. The trunks of Taxodium ascendens and Taxodium ascendens are obvious and completely straight, but the branches in the middle and upper parts of the trunk form broom-like, and the yield is low. The base will also form irregular plate roots.

The leaves and twigs of Taxodium ascendens, Susong 1, Taxodium mexicana and Cunninghamia lanceolata are all pinnately compound leaves. Leaves are strip-shaped, alternate and inserted on branchlets. The leaf length of Taxodium ascendens and Susong 1 is 1.0 ~ 1.8 cm, and they are arranged in two rows on the lateral branches. The leaves of Taxodium ascendens and Cunninghamia lanceolata are smaller, 0.6 ~ 1.0 cm long, and the spiral branchlets are scattered, not two rows. Taxodium ascendens leaves are drill-shaped, slightly inflected, extending spirally on the branchlets, with the lower part clinging to the branchlets and the base extending downward, with a length of 0.3 ~ 1.0 cm. Taxodium ascendens also has pinnate or pinnate, subulate and linear leaf shapes.

Both female cones and male cones are conidia cones, and female flowers and male flowers are the same plant. There are significant differences in morphology, biology and adaptability among different species, varieties and cultivated species of this genus, but the female cones and male cones are very similar in morphology. Female cones are attached to the top of new branches, single or 2-3 clusters, spherical when mature, and 3.5-5.0 mm long. When it is ripe, the scales of the pearl will open. Male cones are inserted on branchlets, which are oval when mature and 3.0 ~ 5.0 mm long. Many male cones form an inflorescence and spread a lot of pollen when they mature.

The mature cones of Taxodium ascendens, Taxodium ascendens and Susong 1 are spherical or oval, with a large volume of 8 ~ 10 cubic meter. Gray-green or brown. The cone of Taxodium ascendens in Mexico is small, with a volume of only 0.7 ~ 1.0 cubic meter, showing a bluish gray color. The cone volume of Chinese fir is between Taxodium ascendens and Taxodium mexicana.

The seeds of Taxodium ascendens are irregular triangles or polygons, with obvious sharp ridges, thick skin, horny, hard, impermeable, nodules and flanges. The seeds of Taxodium ascendens, Susong 1 and Taxodium ascendens are relatively large, with the 1000-grain weight ranging from 40g(25000 grains/kg) to150g (6,666 grains/kg), and the maximum is 220g(4545 grains/kg). The seeds of Taxodium ascendens in Mexico are much smaller, and the 1000-grain weight is only 15g (66666 grains/kg) ~ 50g (20000 grains/kg). The seeds of Chinese fir are between Taxodium ascendens, Taxodium ascendens and Taxodium ascendens.

The root system and "root knee" root system are developed, which can penetrate into the soil layer for more than 3 meters. There are usually 1 ~ several main roots and a large number of fine roots. When Taxodium ascendens, Taxodium ascendens and Susong 1 grow in low-lying wetlands, rivers, lakes, beaches and shores, at the age of 6-8, their roots will grow "root knees" and protrude out of the soil. The height of the "root knee" varies from a few centimeters to 2.0 meters, and the thickness is more than 20 centimeters. General researchers believe that "root knee" is formed by long-term flooding in the original ecological area, which can play a certain role in breathing, ventilation, fixation and storage of nutrients. Taxodium ascendens in Mexico did not form a "root knee" because there was no flooded environment in the original ecological area.

What is temperament?

Taxodium ascendens grows faster, and generally enters the fast-growing period when it is 5-6 years old. The annual growth of tree height is 0.6- 1.0m, the annual growth of DBH is 1.0-2.0cm, and the annual growth of individual tree volume can reach 0. 1 m3. Usually one year is twice as long, with a life span of more than 1000 years and a quantitative maturity of more than 200 years. The results of strict comparative experiments in China are as follows: at the age of 3-5 years, the growth of Sushan 1 is > Chinese fir > flower arrangement > Metasequoia glyptostroboides. The general observation results are as follows: (1) When 18 years old, the tree height growth is: Taxodium ascendens &1000 m;