Importance and Use of Eucalyptus

DR. YOGESH Y. SUMTHANE, ANURUDH YADAV (1325),  ANKIT KUMAR (1326), BHOOPENDRA SINGH (1328), VIKAS GAUTAM (1329), RAVENDRA PRATAP (1330), ANIKET PRATAP (1332), UTKAL YADAV (1333), JITENDRA KUMAR (1335), Upendra Kumar (1336), DEPARTMENT OF FOREST PRODUCT AND UTILIZATION, College of Forestry Banda University of Agriculture & Technology

Eucalyptus globulus is a shrubby plant or a flowering tree belonging to the family Myrtaceae. Genus eucalyptus is known to contain more than 700 species and has widely been used for various purposes since thousands of years in the history of mankind.  

Eucalyptus is basically native to Tunisia and Australia but has also been evident to be found in Africa and from tropical to southern temperate regions of America. Genus eucalyptus further consists of four subspecies which are Eucalyptus bicostata, Eucalyptus pseudoglobulus, Eucalyptus globulus and Eucalyptus maidenii among which Eucalyptus globulus is a medium to large sized evergreen and broadleaf tree that can grow up to the height of 70 m and its diameter can be about 4 to 7 feet.  

Different parts of this plant are nutritionally very important and  therapeutically highly valuable due to specific chemical  composition as its essential oil contain esters, ethers, carboxylic acids,  ketones, aldehydes, alcohols and hydrocarbons along with  monoterpenes and sesquiterpenes. Phytochemical analysis of this  plant has revealed that leaf oil contains 1,8-cineole, α-pinene, p cymene, cryptone and spathulenol. 

INTRODUCTION 

Eucalyptus globulus is a flowering tree that belongs to myrtle family (Myrtaceae). The genus eucalyptus contains more than 700 species and varieties and they have been successfully introduced worldwide. Eucalyptus is native to Australia and Tasmania and also in Africa and tropical to southern temperate America. Variability is prevalent in morphology, growth habit, flower colour, leaves, stems and chemical composition. In case of Eucalyptus globulus, pollen competition favors cross-pollination over self-pollination. 

Controlled pollinations with self-pollen, cross-pollen and a mixture of self-pollen and cross pollen were conducted on three partially self-incompatible trees. Paternity of individual seeds resulting from mixed pollination was determined by isozyme analysis. No evidence for pollen competition was found. Instead, seed paternity reflected the level of self-incompatibility of each trees as determined by separate self-pollinations and cross pollinations. Furthermore, number of seeds set per capsule following mixed pollination was significantly less than that of following cross-pollination in the two least self-compatible trees. These results suggest that both self-pollen and cross-pollen tubes reach ovules following mixed pollination and that of a late-acting self-incompatibility mechanism operates to abort a certain proportion of self-penetrated ovules.

The flowers of Eucalyptus globulus are mainly pollinated by insects but birds and small mammals may also act as pollinating agents.  

 Eucalyptus globulus is known by different names depending upon where you are in the world and its common name is “Australian Fever Tree”, “Tasmania Blue Gum”, “Southern Blue Gum” or “Blue Gum”, “Blue Gum Tree” and “Stringy Bark”.  

In Arabic language, it is known as “ban” or “kafur”.  

In Burmese language it is known by “pyilon-chantha”.  

The trade name of Eucalyptus globulus is “blue gum”.  

In Amharic language it is called “nech bahir zaf”.  

In English language, it is commonly known as “turpentine gas”, “Tasmanian blue gum eucalypt”, “Tasmanian  blue gum”, “southern blue gum”, “fever tree”, “blue gum eucalyptus” and “blue gum”.  In Japanese language, it is called “yukari-no-ki”.  

In Spanish language, it is known as “eucalipto”.  

In Swahili it is known as “mkaratusi” and in Tigrigna language it is called “tsaeda kelamitos”.  

Eucalyptus globulus is a complex species as consist of four further subspecies which are Eucalyptus bicostata, Eucalyptus pseudoglobulus, Eucalyptus globulus and Eucalyptus  maidenii. The only one variety of eucalyptus globulus is Eucalyptus globulus var. compacta  Labill-Dwarf blue gum.  

Eucalyptus oil has numerous traditional uses especially in non-prescription pharmaceuticals but the market is small. Currently somewhere between three and five thousand tonnes are traded each year on international markets, with only two or three hundred tonnes being produced by Australia. Eucalyptus oil based products have been used as a traditional non-ingestive treatment for coughs and colds. 

 Demography/Location  

• Eucalyptus globulus can be grown in variety of climatic conditions and environmental modifications but the best known optimum conditions are evident to be found in countries having warmer climate. Eucalyptus is preferably found in Albania, Tunisia, Argentina, Bangladesh, Cambodia, Brunei, Eritrea, Greece, Ethiopia, Indonesia, Italy, Israel, Laos, Kenya, Malaysia, Myanmar, Morocco, Namibia, Nigeria, Nepal, Pakistan, Spain, Philippines, Sudan, Uganda, Tanzania, Thailand, Malta and United Kingdom.    
• Australia is covered by 92,000,000 hectares that is equivalent to 227,336,951 acres of Eucalyptus globulus forest thereby comprising three quarters of the whole area covered by native forests. Similarly, total area of Eucalyptus globulus that is planted in India is supposed to be exceeding 2,500,000 ha.  
• In the year 2006, it comprised about 65 percent of all plantation hardwood in Australia with about 4,500 km planted area. Eucalyptus globulus is the primary source for eucalyptus oil production all around the world. During the last ten years, in the north western regions of Uruguay, Eucalyptus globulus was one of the major cultivated crop.  That zone has a potential forested area of 1,000,000 hectares, approximately 29% of the national territory dedicated to forestry among which approximately 800,000 hectares are currently forested by monoculture of Eucalyptus globulus. In Brazil, there are around 7 million hectares planted area that can produce upto 100 cubic metres per hectare per year.  

Botanical Specifications 

• Eucalyptus globulus is a broadleaf evergreen plant that can attain the maximum height of about 70 m as evident to found in Europe. Although more than 700 different species of this plant are found to exist but Eucalyptus globulus is the most widespread among all other species in East Bay. It is an aromatic plant that has straight trunk and well-developed crown with tap root system exceeding the depth of 10 feet.  
• Evergreen, large to very large tree up to 70 m tall; bole straight, cylindrical, up to  200 cm in diameter; bark surface usually smooth, white to cream, yellow or grey;  crown narrow, but rounded in trees growing in the open.  
• Leaves alternate, pendulous, simple and entire; stipules absent; petiole rounded, channeled or flattened, 1.5–5 cm long; blade narrowly lanceolate to lanceolate, sometimes sickle-shaped, (10-12–28(–30) cm × 1–3(–4) cm, acuminate at apex, leathery, glabrous, pinnately veined, aromatic when crushed.  
• Inflorescence an axillary, simple, umbel-like condensed and reduced dichasium, 1–7- flowered; peduncle flattened or rounded, up to 25 mm long.  
• Flowers bisexual, regular, whitish; pedicel up to 8 mm long; flower buds top-shaped,  divided into an obconical, ribbed or smooth hypanthium (lower part) 5–12 mm × 5–17 mm, and a flattened, hemispherical operculum (upper part) 3–15 mm × 5–17 mm,  having a short knob; stamens numerous; ovary inferior, 3–5-celled.    
• Fruit an obconical to globular capsule 5–21 mm × 6–24 mm, enclosed in a woody hypanthium, opening with 3–5 somewhat exserted valves, glaucous or not, many seeded.  
• Seeds 1–3 mm long. Seedling with epigeal germination.  
• Eucalyptus globulus also grows in mild, warm and tropical climates having mean annual  temperature ranging from 3-22 to 21-40°C, but cannot live at temperatures lower than -5°C  and mean annual rainfall ranging from 250 to 2500 mm.
• Eucalyptus globulus are cultivated in Mediterranean area and grow until 350 meters over the sea level. Usually the young plants are planted in spring or at the end of summer. Eucalyptus globulus should be grown in climate with high humidity otherwise suffers burning of leaf border. It can grow in wide range of soils and with limited water supply.
• The soil type grows best on deep, silty or loamy soils with a clay base and accessible water table. It is one of the species found to be most tolerated to acid soils and soils optimum pH ranges from 5.5 to 6.5. In  India, location was 10.2572°N latitude; 78.8861°E longitude; 216 ft above sea level with  average temperatures ranging between 33.5°-42.2°C and 1043.31 mm annual rainfall. The soil type of the study area is red soil.  

Properties  

• The heartwood is pale grey to pink or reddish brown, and fairly distinctly demarcated from the paler, up to 5 cm wide sapwood. The grain is often interlocked, sometimes straight with patches of spiral grain; texture moderately coarse. The wood often contains gum veins. Brittle heart is common.  
• The wood has a density of 670–920 kg/m³ at 12% moisture content, but wood from plantations often has a lower density than that from natural stands. Shrinkage is extremely high: from green to oven-dry 6.5–13.2% radial and 11.7–19.1% tangential. Air drying may pose problems, because twisting and collapse can be severe. Care must be taken in kiln drying to prevent tangential checking, and quarter-sawing is recommended before drying as well as initial air drying to 30% moisture content. A delicate balance of air drying, kiln drying, and steam reconditioning can address problems with collapse. The dried wood is not stable in service.  
• The wood is hard and strong. At 12% moisture content, the modulus of rupture is 105–213  N/mm², modulus of elasticity 10, 600–20,400 N/mm², compression parallel to grain 56–82  N/mm², shear 8–10 N/mm², cleavage 28–35 N/mm and Janka side hardness 6850–11,480 N.    
• The wood is rather difficult to work, due to its high density and the presence of interlocked grain. Blunting of sawteeth and cutting edges is severe. Nailing is best done after per boring. The gluing properties are satisfactory. The wood bends well and accepts most finishes, and it sands to a smooth surface.  
• The wood is moderately durable at best, being susceptible to insect, termite and marine borer attacks. The sapwood is susceptible to Lyctus borers. The heartwood is resistant to treatment with preservatives, but the sapwood can be impregnated.  
• The wood of Eucalyptus globulus has an energy value of 18,000–19,400 kJ/kg. It is recorded to burn freely, leave little ash and carbonize easily to good charcoal.  
• The wood fibres are (0.3–) 0.8–1.1(–1.5) mm long, with a diameter of (10–) 15–21 (–28) μm and an average wall thickness of 3.0 μm. Pulp can be produced using the sulphate (kraft), sulphite, or bisulphite processes, and is usually bleached. Wood from 10-year-old trees from Australia contained 45% cellulose, 23% glucuronoxylan and 27% lignin. A bleached kraft pulp yield of 56% was obtained, with 3.2 m³ wood needed to obtain 1 t of bleached pulp.    
• The leaves yield 0.75–6.0% essential oil, with 44–90% 1,8-cineole, and also camphene (up to  23.1%), α-pinene (2.6–20.1%), globulol (up to 7.3%), limonene (0.5–7.8%), β-pinene (0.1–2.7%), α terpineol (0.1–5.8%) and p-cimene (0.1–8.2%). Several euglobals, having acylphloroglucinol monoterpene or sesquiterpene structures have also been isolated. The essential oil has shown antibacterial and antifungal activity. It also has anti-amoebic activity and  larvicidal activity against Anopheles stephensi. Essential oil extracts have shown in-vivo analgesic and anti-inflammatory effects in rats and mice. There is no evidence for antimalarial action, and the belief in the antimalarial effects of Eucalyptus globulus may stem from its history of being planted to drain swamps in southern Europe, and hence its indirect role in malaria control. Poisoning from the essential oil is described in humans.
• Leaf extracts have shown antibacterial, antifungal and antiviral effects. Water extracts of the leaf have shown antihyperglycaemic and molluscicidal activities. Ether extracts of the leaf showed anthelmintic activity against Strongyloides stercoralis and Ancylostoma spp.  A decoction of the leaves had in-vivo diuretic activity in rats. An ethanol extract of the leaf and a decoction of the seed have shown in-vivo anti-inflammatory activity in mice and rats. Euglobals from the leaf have shown anti-inflammatory effects, inhibitory effects on the activation of Epstein-Barr virus and anti-tumour activity. Powdered leaves and leaf extracts provide protection against the pulse storage pest Callosobruchus maculatus.  The leaves contain tannins (ellagitannin, gallotannin and catechin derivatives) and flavonoids (flavone glycosides with the aglycones quercetin, myricetin, kaempferol and  rutin).  

Sropagation & planting  

• The 1000-seed weight is 2.5–17 g. Airtight storage at 4–6% moisture content and temperatures below 0°C is recommended, although viability can be maintained for several years in airtight storage at 3°C with 6–10% moisture content. Seed orchards from grafted material can be top-pruned before seed abscission to more easily harvest seed from the ground. Harvesting in this manner can be started as early as 5 years after orchard establishment. Seed thus produced has a germination rate of up to 80% in 4–14 days.  Seedlings are raised in containers filled with sterilized soil, leaving 2 seedlings per container. Young plants are very susceptible to insect attack.  
• In most tropical and subtropical countries out planting in the field occurs when the plants are 3–6 months old and 15–35 cm tall. Where Eucalyptus globulus is planted in monoculture plantations, de-brushing by tractor is often carried out. This is followed by ploughing and disking. In situations where this is impractical due to slope, rocky soil or lack of equipment, seedlings can be planted in holes in soil worked to at least 1 m in diameter around the hole. 
• In all cases, it is preferable to leave some months between soil preparation and planting, to allow clods of soil to break down. On slopes in particularly wet or dry climates it is recommendable to prepare raised rows either to drain excess moisture or to capture scarce moisture, and in both cases plants go on the top of the mounds. Initial plant spacing ranges from 1 m × 1 m to 3.3 m × 3.3 m, depending on the purpose of the trees (use for pulp, fuel and  posts allows closer spacing than use for sawn timber).
• For mechanization, a distance between rows of 3 m is necessary, and 3 m × 3 m is the minimum spacing necessary for mechanical weeding in two directions. A planting density of 4500 trees/ha and a survival rate of 64% are reported from Ethiopian community woodlots used for fuel and wooden poles. In Ethiopia farmers sometimes spread branches with mature fruits on the site, and when the fruits have opened and the seeds have been dispersed, the soil is kept moist to ensure germination. When the plants have established, the branches are removed, and later the stand is thinned to a suitable spacing.  
• Planting should be as early as possible after the start of the rainy season, to benefit fully from the rains and from the residual heat in the soil after a hot dry season. The moisture in the rootball gives some resilience to the seedling, allowing it to withstand a dry spell of up to 2–3 weeks between planting and the onset of consistent rains. If there are losses due to adverse conditions, it is imperative to plant replacements as soon as possible so as to maintain a uniform stand. Fertilization of the young plants can be effected from a few weeks to 3 months after planting by dressing a balanced fertilizer (according to soil conditions) at a distance of 10–30 cm from the plant.

 Management and harvesting

• Weeding is critical in the first years of development, but becomes less important after closure of the canopy. Fertilization is common but not universal for young plants. For the production of timber, plantations are thinned at 6 and 10 years after planting, with up to 70% of the trees being removed.  
• The tree coppices well, and after harvest a number of shoots are allowed to coppice from the stump. In the first two years after harvest these are thinned to leave 1–3 shoots, depending on a preference for fewer, larger shoots or many smaller shoots.
• It is also possible to thin at 2–3 years and thus have an appreciable auxiliary harvest of small poles in addition to the main harvest years later. With each successive harvest, fewer of the cut stumps coppice, which is why normally 3 coppice harvests are considered the maximum before necessary replanting. However, a site in the Nilgiri Mountains (India) is said to have produced satisfactorily for over 100 years on 10 year coppice rotations.    
• Replanting of an old plantation requires the complete removal of old stumps. This is an onerous task, accomplished either by meticulous shredding of stems and lignotubers or by chemical treatment. The lignotubers and root mass can also theoretically be dug up to be sold as fuelwood.  
• Harvesting is usually done on short rotations of 8–15 years for densely planted plantations destined for production of posts, pulp or fuelwood, but rotations may be as short as 5–7 years in Ethiopia. Rotations of up to and beyond 30 years are given to Chilean trees destined for processing as sawn timber.
• Harvesting of Eucalyptus globulus on short rotations is accomplished by cutting the entire tree at 10–12 cm above the ground with a chainsaw or manual saw, making the cut on a slope to allow water to run off of the stump.  Up to three coppice harvests are usually taken, with the stand quality deteriorating after the third coppice harvest.
• Another harvesting option is the progressive thinning of the plantation to yield harvests of increasing size at various intervals. For example in Uruguay a 16-year rotation is practiced, with cuttings at 6 and 10 years that eliminate 70% of the planted trees and leave space for a harvest of large trees at 16 years   

Uses  

• The wood of Eucalyptus globulus is used for poles, posts, construction, low-grade veneer, plywood, flooring, furniture, tools, boxes, crates, pallets, railway sleepers, fibreboard and particleboard. It is also suitable for marine construction, ship and boat building, vehicle bodies, toys and novelties, turnery, interior trim, core stock, joinery and mine props.    
• Eucalyptus globulus is very important as fuelwood and for charcoal making, and it is an important source of pulp for the production of printing, writing, specialty and tissue papers.  
• The leaves of Eucalyptus globulus are the principal source of eucalyptus oil in the world.  Eucalyptus oil is used for medicinal purposes, especially against cough and as an expectorant, but it also has febrifuge, tonic, astringent, antiseptic, haemostatic and vermifugal properties.  
• The flowers are a source of nectar for bees, giving honey with a flavour like muscat grapes.  The dense root system makes the tree suitable for erosion control. Eucalyptus globulus is also used for windbreaks, and young plants make a useful living fence because they are unpalatable to livestock. It has been used in land reclamation, including the drying up of swamps. The tree has ornamental value. Carbon sequestration in pulpwood plantations of Eucalyptus globulus is a modern use.  
• In African traditional medicine, an infusion or decoction of the leaves is taken, or applied externally in baths, lotions or enemas, against asthma, bronchitis, tonsillitis, colds, urinary problems and haemorrhages. The vapour of boiled dried leaves is inhaled against asthma, cough, flu, croup and diphtheria, or fine leaf powder is inhaled.
• In Sudan a decoction of the leaves is drunk to treat malaria and in Madagascar the leaves are heated and the vapour inhaled against this disease. Powdered or bruised leaves or a leaf decoction are applied on abscesses and wounds. A paste of powdered leaves is rubbed in against rheumatism. In Kenya a leaf decoction is used in a bath to treat chickenpox in children. In Ethiopia a leaf extract is gargled for treatment of meningitis. In southern Africa the leaves are used against stomach-ache. Gum resin from the plant is used against diarrhoea. Various leaf preparations are used as insect repellent, and in Kenya the fresh or dried leaves are used for controlling snails  

  Production & international trade    

• For 1995 it was estimated that worldwide Eucalyptus plantations amounted to about 14.6 million ha, of which 1.8 million ha in Africa, much of this in South Africa.    
• It is estimated that worldwide up to 2.5 million ha are planted with Eucalyptus globulus, mostly in regions with a temperate climate, e.g. in Spain, Portugal, Chile and Australia. In Ethiopia about 145,000 ha of Eucalyptus have been planted, a large proportion consisting of Eucalyptus globulus.  
• In southern Africa the leaves are sometimes sold in markets for medicinal use. China dominates the world market of Eucalyptus oils.