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China - Metasequoia: the national fossil tree

Chao Chin Ju

CHINA'S "FOSSIL TREE" once thought extinct - now a bright future (CHAO CHIU JU)

A METASEQUOIA SEEMING growth potential of more than 35 metres (JOHN KUSER)

· There exists in the world a living fossil tree - the Metasequoia glyptostroboides (dawn redwood), native to China

This old and rare tree species was thought, until recently to be extinct. Nobody knew that in a remote comer of China people had kept and propagated it.

In the 1940s, two Chinese scientists, Hu Shian Sou and Cheng Wan Chun, discovered the M. glyptostroboides in Lichuan County, in Hubei Province. They identified the species by its fossil, one of the 10 fossils corresponding to the 10 tree species of the Metasequoia genus known to scientists up to now. To commemorate this discovery, the species was given the name "living fossil" in scientific circles.

This species of Metasequoia has strong adaptability and is quick-growing. Its straight and full-boled stems indicate a fine qualify timber which can be used to make paper, as well as in construction and in making furniture and farm tools. It is an excellent species for afforestation, and the planting of Metasequoia in quantity could play an important role in fuming the land green, increasing timber output and beautifying the environment.

Since 1948, it has been planted throughout the country and has been introduced in more than 50 countries in Asia, Africa, Europe and America where it grows very well. In high-latitude areas such as Leningrad, Copenhagen and Alaska, for example, it can grow even in winter, at sub-zero temperatures. Very few species are so adaptable that they can be introduced in such a variety of areas.

The Metasequoia is a large deciduous tree which can reach 37 m in height and 2.2 m in breast diameter. The range of its adaptation to climatic conditions is broad. It grows well in areas where the annual average temperature is about 12° -20°C. It is winter-hardy. Even in northwest

China, along the Wei River valley, where the absolute lowest temperature is 18.7°C, and in the Lüda area in northeast China, where the minimum winter temperature is 19°C, it survives and grows. It thrives equally well in areas where annual precipitation is 1000 mm. It also adapts well to dry climates if there Is irrigation during the very dry season, but sustained dryness will kill It. It can grow on light saline and alkaline land (salinity below 0.2 percent). Its distribution in its original location is at an altitude of between 900 and 1 500 m, but chiefly at one of 1 050 m. The best results were obtained when it was introduced to alluvial soil on plains and beside rivers, and to wetter foothills where slopes are gentle.

Quick growth is one of the main advantages of the Metasequoia. In its provenance its average annual vertical growth is 30-80 cm and its average annual breast diameter expanse is 1 - 1.75 cm. The leading shoots of the continuous height growth (1.43 m) appeared when it was 10- 15 years old and the leading shoots of the continuous breast-diameter expanse (2.1 cm) appeared when it was 20-25 years old. In the introduced areas, the highest value of its continuous height and breast-diameter development appeared even earlier and the absolute value was also greater. This shows its characteristics of quick growth and high yield. The growing pattern in some areas in southern China indicates that, under ordinary planting conditions, it can grow into matured timber in about 15-20 years. Recently, thanks to intensive cultivation, it has grown even faster than before. For instance, in Huanghu County, Hubei Province, its average height was 9.5 m and its average breast diameter was 10.5 cm when it reached seven years of age. In the Hongqi River area, Jiangdu County, Jiangsu Province, the average height was 7 m and the average breast diameter was 11.2 cm when it was four years old. Its mature period could be accelerated starting at 10-15 years if site conditions are suitable and cultivation measures intensive.

Chinese foresters have accumulated techniques and experience through age-long practice in the management of this tree.

Seedling cultivation by sowing is done by establishing nurseries in a flat area with convenient drainage and irrigation, in fertile and loose sandy soil. Careful preparation of the soil is necessary before sowing, which takes place from the last part of March to the first half of April, when soil temperature is above 12°C. After sowing, frequent watering is required. Alternation of dryness and wetness should be avoided, and proper shade should be provided for the young seedlings.

Seedling cultivation by cutting is, at present, the best way for the reproduction of Metasequoia, because there are very few mother trees and the yield of seeds is limited: in fact, seedlings cultured by sowing cannot meet the needs of large-scale afforestation.

Spring propagation with matured, healthy branches as cuttings is the method generally used at present.

Cutting can be done in early summer (the last 10 days of April) with the sprouts, in early autumn (the first half of October) with the tops of semi-matured branches and in late autumn (the second half of October and the first part of November) with nearly mature branches.

Treating the low parts of the cuttings with a naphthylacetic acid solution before cutting accelerates early rooting and increases the rooting rate and quantity.

In afforestation, the spacing should not be too close. Spacing of 2x3 m can be used in large areas, and 2-m spacing can be used in planting in individual rows. It is best to use two to-three-year-old seedling trees from late autumn to early spring. The survival rate is comparatively high if planting is carried out at the end of winter. From then on, timely tending and pruning are necessary.

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