CHINESE Paulownia: A MARVELOUS TREE SPECIES FOR AGROFORESTRY
Zhang Huaxin
Research Institute of Forestry of Chinese Academy of Forestry
Abstract
Paulownia is considered one of the best trees for agroforestry. The genous is native to China and a number of species of it are extensively used in different type of agroforestry through out the China. The species of genus Paulownia are multipurpose and provide a number of products. This paper summarizes the distribution of the genus in its native range, important structural attributes, uses and agrororestry models developed using the Paulownia species as woody component.
Introduction
Paulownia, originated from China, is a marvelous tree species, characterized by fast growth, good Wood quality, multiple uses, wide distribution at range and easy propagation. It has also a unique biological character, i.e. its root system grows in deep earth and its crown develops in loose structure, which make it suitable to be intercropped with crops arable or mixed planting with other shade-enduring trees. The Paulownia wood is the traditionally exported from China, which is extremely welcomed at the international market.
Since 1960s, Paulownia has been extremely popular and appreciated by Chinese farmers. The Paulownia and crops intercropping models have been applied and extended to 15 million hectares in rural areas of the central plans of north China. The mixed planting models of Paulownia with other economic plants have also been applied and extended to an area of 20,000 hectares in the hilly areas of south China. Up till now the total number of Paulownia trees growing in China is as many as 1 billion including those grown as the shelterbelts at the canal banks and road sides or for the ornamental forests around the houses and villages.
The rapid development Pwulownia planting in China has been well recognized by many other countries. The Paulownia trees have been introduced to more than 20 countries, such as Australia, New Zealand, India Thailand , Pakistan, United States, Italy, France, Turkey, Philippines, Uruguay, Panama, Brazil and Agentina, etc. We believe that Paulownia, as a common property of human being, can bring benefits not only to the Chinese people but also to those in other countries.
Species and Their Distribution
Paulownia is a deciduous tree species belongs to Scrophulariaceae family. The Paulownia species that are distributed in the areas north to the Yangtze River are: Paulownia elongata, p.catalpitolia and P.tomentosa, among which p.elongata grows faster and is suitable for intercropping with arable crops, while the other two species grow slower but have better wood quality. The Paulownia species that distributed in the areas south to the Yangtze River (subtropical zone) are: Paulownia fortunei, p.australis, p.albiphloea, p.fargesii, p.kawakamii and p.taiwaniana, among which p.fortuner has the fast-growing characters and also has straight stem, while p.kawakamii grows slower with a poor stem form. P.fargesii can grow at the sites with elevation of 1,230-2,000 meters.
The distribution range of Paulownia is extremely wide in China, from north line from Liaoning (south to Xiongyue) to Beijing, Taiyuan, Yan’an and Pingliang, down to south line of Guangdong, Guangxi and south Yunnan, going east to Taiwan and other coastal provinces, and in the west to Minshan Mountain in Gansu and Gongshan Mountain in Gaoli of Yunnan, i.e., in the latitude from 20° to 40°N and the longitude from 98° to 125° E.
The climatic conditions vary so much among the paulownia distributed areas, with their annual mean temperature varying from 10℃ to 22℃. The best temperature range for Paulownia growth is 24℃ to 29℃. The lowest temperature that Paulownia can resist is -20℃ for p.tomentosa, -16℃ for p.elongata and -13℃ for p.fortunei. The growth of paulosnia is negatively influenced when temperature is higher than 38℃. Paulownia can adapt to wide-range of precipitation from 500mm to 2,500 mm. The suitable edaphic conditions for Paulownia growth are fertile sandy loam to heavy loam soils with loose structure and salt content less than 0.05%. Paulownia has little tolerance to water logging and may soils with loose structure and salt content less than 0.05%. Paulownia has little tolerance to water logging and may die when its growing site is submerged for a short period of time (in July or August). Paulownia can not be grown in mixed planting with other fast growing broadleaved trees.
Impact and Features
Fast Growth
Paulownia grows fast, so that its stem is large enough in girth and length enough for some purpose in 7-8 years age if the appropriate management is given. There is saying often used by the farmers to explain the growth of Paulownia, i.e., “one-year-old tree looks like a thick stick, 3-year-old tree looks like a big umbrella and 5-year-old tree can be used as saw log”. For example, a P.fortunei tree growing in Guilin city, Guangxi Autonomous Region had its DBH of 77 cm, height of 21 m and volume of 3.67 m3 when it was 11 years old, and still a p.fortunei tree growing in Guanyan County, Guangxi Autonomous Region had its DBH of 45 cm, height of 21 m and volume of 1.171 m3 when it was only 5 years old , which is the best one of fast-growing Paulownia trees in China.
1,2 and 3 years old Paulownia
http://dpishop.dpi.qld.gov.au/bookweb/details.cgi?ITEMNO=9780724267958
Paulownia is a fast-growing forestry species that has potential in Australia to produce harvestable timber in six to eight years. Possibilities include growing paulownia as an intensive horticulture crop on high-quality soils with intensive management, or in small wood-lots as an add-on to other farm enterprises. The most likely applications for paulownia appear to be in the joinery and mouldings industry. Uses such as picture framing, arches, cornices, cabinet making and wall paneling capitalist on the timber's good working qualities, good stability and medium strength-to-weight ratio. This report brings together current knowledge and experience in growing paulownia in Australia, including the timber's properties, market situation, and production and processing issues. It also provides useful costing on establishment, maintenance, harvesting and likely returns, which will assist interested parties in making a commercial assessment. Anyone considering entering the industry should be aware that this is a very new industry in Queensland. The Department is not in a position, at this stage, to advise farmers and others on the likely commercial success of a paulownia-growing enterprise.
ISBN 0724267956, Soft Cover, 1998
Growth rates
The growth of paulownia is very dependant on site conditions and the age of the tree. One example presented by the Chinese indicates that paulownia may reach 40-50 m in height and have a diameter of greater than 2 m when mature, but trees of this size under cultivation are rare. Rapid early growth rates have been observed, but may not be sustained as the tree ages. In the first year of growth trees may reach 4-6 m in height, growing another 2-3 m in the second year. Paulownia growing on good sites in China and Japan may be 10 metres high with a clear bole of 5 m and diameter of 22 cm at breast height in 4 years. At these sites it is usual for trees to have a diameter of 45-50 cm at 10 years of age, with production of 12 m3/ha/year. Paulownia plantations in Queensland and New South Wales are being managed to produce sawlogs over a 10-15 year rotation.
Natural occurrence
Paulownia occurs naturally in China, Taiwan, Cambodia, Laos and Vietnam. Its natural distribution ranges from tropical through to cool temperate climates, on sites with average rainfall ranging from 500 mm to over 2,000 mm per annum. It occurs from just above sea level up to an altitude of 2,400 m.
The nine species of paulownia are very similar in appearance and timber properties. Paulownia tomentosa and Paulownia fortunei are currently being grown in Australian plantations. As yet, there are no scientifically designed trials to determine the most appropriate species, hybrids or provenances for different sites across Australia.
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Detail of the zone of apical growth of a young Paulownia in the heat of development.
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Paulownia soon after being planted, alongside the same unit ten months later (+ 4,5 ms) and forty months later (+ 7,5 ms.)
P. Kawakamii planted in April.Over 6 ft in August of same year. Austin,Texas
This trunk belongs to the same Paulownia. The photos have been carried out to the 12, 24 and 40 months of age.
Paulownias during his first months of development, with a height of about two meters
http://www.agrodesierto.com/paulownia.html
Quality Wood for Multiple Uses
Paulownia wood has many special properties. As one of the lightest wood tree species in China, Paulownia wood has the properties of high resistance to distortion and splitting, high resistance to insect damage, low coefficient of shrinking index, negligible moisture breaking, easy for drying, easy for processing, easy for sculpting, pretty in strains, without smell, and good at acoustics and insulation characters.
The Paulownia wood can be used for many purposes. It can be used as the roof purling or beam for building house in rural areas, and also can be used for making window frame, door or furnishing board. It can also be used for making furniture, such as trunk, cupboard, be board, bellows, food-packing box, water bucket, stout carrying pole, wooden tile, aqueduct, water cart etc. It is also good raw material for making musical instruments. In Japan and Southeast Asia, the Paulownia wood is usually used for making handy crafts, such as flower vase, screen and medal box. The Paulownia wood can also be used for industrial purposes, such as for making wooden model, packing board for transportation, vehicle or shipboard and plywood. In Japan, the Paulownia wood is used mostly for making thin veneer as pasting surface of furniture.
The leaf, flower, fruit and bark of Paulownia are good materials for Chinese medicine. In the recent years, the Paulownia was used successfully for treating many body disorders. The leaf and flower contains rich nutrients that benefit to human health. Based on the analysis, it contains bulk fats 11.38% in leaf and 4.65% in flower, glucose 3.76% in leaf and 3.97% in fruit, soluble sugar 4.89% in leaf and 10.58% in fruit, bulk proteins 16% in leaf and 27% in fruit. In addition, in the leaf of Paulownia contains 3.09% of nitrogen, 0.19% of phosphorus and 0.41% potassium. So, the leaf and fruit are good fodder for feeding sheep, pig and rabbit, and also are good organic manners.
UTILIZATION OF ROYAL PAULOWNIA
by Bob Wright
Staff Forester - Forest Products Utilization
WOOD CHARACTERISTICS
The specific gravity of royal Paulownia ranges from 0.23-0.30, with an average of 0.28. For comparison: Eastern cottonwood has a specific gravity of 0.40; basswood, 0.37; and yellow poplar 0.42. Paulownia is one of the lighter woods known. It is easy to dry and drying defects are few. It air-dries in 30-60 days and can be kiln-dried in 24-48 hours. The wood virtually does not split, crack, or check during the drying process. Paulownia is light to almond in color and readily accepts stain. It has excellent machining, carving, and working qualities. Shrinkage and expansion with change in moisture content is minimal as compared to most woods. Paulownia has a natural resistance to decay and has the ability to breathe and keep moisture out. In addition to all the above, it is strong, especially for its weight.
USES
Paulownia has originally been mainly used in the Orient, with furniture as the major application. Drawer sides and backs, veneer, dressers, chests, and bedroom suites make up most of the furniture built from Paulownia. Musical instruments, especially the koto, comprise another sizeable group of products. Other items made from Paulownia are gift boxes and cases, crating for air shipments, wooden utensils, shoes, bowls, ornamental carvings, coffins, and even hair-growing extract from the leaves.
Logs exported to the Orient are used primarily for furniture and musical instruments. The close-grain (high-density) wood from the U.S. offers the qualities desired to manufacture the higher-value products. Logs and lumber exported from China, Taiwan, and Brazil are used for boxes, drawer sides and backs, shoes, and the center (core) of veneer.
In the West the interest and demand in Logs and lumber have been constantly growing during the past few years and Paulownia seems to emerge as a viable alternative to a range of other timbers previously used in various fields.
LOG GRADES AND PRICES
Paulownia log grades vary among different buyers and companies. Following is a list that reflects qualities required by most firms:
PAULOWNIA LOG GRADES*
AA: Minimum of 16" on small end, free from defects, straight, centered pith, close grain (approximately 6 rings per inch).
A: Minimum of 14" on small end, free from defects, straight, centered pith, close grain.
B: Minimum of 12" on small end, few defects, straight, close grain.
C: Minimum of 10" on small end, allowable defects, close grain.
D: Minimum of 9" on small end, allowable defects, close grain.
E: Minimum of 9" on small end, allowable defects.
*All logs must be at least 7 feet in length.
Prices paid for Paulownia logs continue to be the highest paid for any species growing in the West. It is, of course, because of this that so much interest has been shown in growing Paulownia as a timber species in the U.S. Following is a list of prices paid for Paulownia logs in Tennessee from 1977 to 1991.