Casuarina cunninghamiana (Australian beefwood)

C. cunninghamiana is a fast growing species with prolific seeding ability.Its preferred habitat is close to water, allowing its seeds to be dispersed by both wind and water. Its potential impact on native species assemblages is being closely monitored in regions such as South Africa and Florida, USA. C. cunninghamiana was grown in South Africa as an ornamental, for shelter and to stabilize sand dunes but is now registered as a category 2 declared invader according to the Conservation of Agricultural Resources Act, 1983 (Henderson, 2001). It was among several species of Casuarina that were introduced into Florida, USA in the 1890s and it may have already escaped from cultivation by the early 1900s (Anon., 2003). Elfers (1988) described it as 'the hardiest Casuarina' found mainly in central and northern Florida. It is listed as a category 2 invasive plant species by the Florida Exotic Pest Plant Council, which means that C. cunninghamiana has increased in abundance or frequency but is not yet thought to have caused ecological damage (FLEPPC, 2001). It is also listed as a prospective invasive species for the Pacific Islands (PIER, 2002) on the grounds that it is found on some of the Pacific islands, may be exhibiting invasive behaviour and is known to do so in other regions. It is classified as potentially invasive by Binggeli (1999).

The casuarinas are a group of 96 species of trees and shrubs which comprise the family Casuarinaceae (Wilson and Johnson, 1989). They have been placed in four genera: Allocasuarina L. Johnson, Casuarina L., Ceuthostoma L. Johnson and Gymnostoma L. Johnson. A useful summary of the taxonomy, distribution and genetic variation in casuarinas is provided by Turnbull (1990). The genus Casuarina comprises 11 tree species, including 4 species with two subspecies each (Boland et al., 1996), although narrower species circumscriptions recognize up to 17 species. It is mostly endemic to Australia, but with representatives in South-East Asia and the Pacific Islands. The generic name is from the Latin 'casuarius' (a cassowary), likening the pendulous branchlets to the drooping feathers of the cassowary.The specific epithet for C. cunninghamiana is after Alan Cunningham (1791-1839), an explorer and botanical collector. Two subspecies have been recognized: subsp. cunninghamiana in eastern New South Wales and Queensland; and subsp. miodon in the Northern Territory extending to the far northwest of Queensland (Wilson and Johnson, 1989). The epithet 'miodon' comes from the Greek 'meion' (Latinised as 'mio', meaning few) and odous or odontis (Latinised as 'odon', meaning a tooth), referring to the relatively few leaf-teeth.C. cunninghamiana is closely related to C. glauca, which differs in having larger cones, 12-16 leaf-teeth, and generally coarser and subglaucous foliage. C. glauca tends to grow in estuarine locations, tidal reaches and brackish water. Natural hybrids occur between C. cunninghamiana and both C. glauca and C. cristata (Wilson and Johnson, 1989). Hybrids with C. glauca are quite common in cultivation (El-Lakany et al., 1990a).C. grandis, which is native to southeastern Papua New Guinea, was formerly regarded as a tropical form of C. cunninghamiana, and has a similar distribution along freshwater rivers.

In Australia, C. cunninghamiana is the largest species of the Casuarinaceae, reaching 20-35 m tall and with a stem diameter up to 1.5 m. As subsp. cunninghamiana, this riverine species forms a handsome tree of tall stature with pendulous, grey-green, needle-like foliage. It attains its best development in southeastern Australia. Subsp. miodon from the Northern Territory and northwestern Queensland (Australia) rarely exceeds 12 m tall and has a straggly appearance. C. cunninghamiana has finely fissured and scaly, grey-brown bark. A contemporary description of the species as comprising two subspecies is provided by Wilson and Johnson (1989). General descriptions with illustrations are provided by Boland et al. (1984), and Doran and Turnbull (1997). Vegetative growth in casuarinas consists of both permanent branchlets of indeterminate length that eventually form the main stem and branches of the tree, and also deciduous (non-permanent) branchlets of determinate length which fall as entire units (e.g. after 1-2 years of growth in C. cunninghamiana) (Boland et al., 1984; 1996). The needle-like deciduous branchlets are composed of jointed articles, each with a series of photosynthetic ridges known as phyllichnia. The stomata are found in the grooves between each ridge. Each ridge terminates in a small triangular tooth which is the tip of a reduced leaf. Collectively these form a whorl of leaf tips at the apex of each article. The soft, grey-green, deciduous branchlets of C. cunninghamiana are drooping in vigorous specimens and erect in depauperate specimens. Their phyllichnia have a central rib and are prominently angular in subsp. cunninghamiana, but tending towards flat in subsp. miodon. Articles are 4-9 mm long, 0.4-0.7 mm diameter and mostly glabrous. The leaf-teeth on new shoots are erect, 0.3-0.5 mm long, marcescent, yellow at base, darker brown toward apex, and in whorls of 8-10 in subsp. cunninghamiana; and not marcescent, uniformly yellow and in whorls of 6-7 in subsp. miodon. The species is mostly dioecious with individuals bearing unisex flowers in an approximate 1:1 mix of both sexes, but monoecious individuals exist (Boland et al., 1996). Male flowers are borne in spikes, 0.4-4 cm long, at the tips of the annual flush of new deciduous branchlets and are arranged in whorls with 11-13 whorls/cm of spike. Anthers are 0.4-0.7 mm long. Fruiting cones (correctly called infructescences) arise from the leaf axils on the permanent branchlets. They are small, oval and reddish, and comprise about 50-60 flowers. The cones are small, sparsely pubescent, subglobose, about 7-14 mm long and 4-6 mm diameter, bracteoles broadly acute to acute and on a peduncle 2-9 mm long. The individual fruit is a small, pale greyish, winged single-seeded samara 3-4 mm long, supported by two bracteoles and one bract.

C. cunninghamiana is endemic to Australia, and has a natural range of 12°-38°S and an altitudinal range 0-1000 m. Subsp. cunninghamiana occurs from southern New South Wales to northern Queensland, extending inland for up to 400 km. Typically it occurs fringing freshwater rivers and streams. Subsp. miodon is found along the larger rivers in the Northern Territory, and occurs in the far northwest of Queensland, adjacent to the Gulf of Carpentaria. C. cunninghamiana is still plentiful throughout most of its extensive natural distribution. This is due, in part, to its habitat along water courses where its spreading roots play a role in stream bank stabilization, which discourages clearing.

C. cunninghamiana occurs under a wide range of climatic and edaphic conditions, and has proven very adaptable when planted as an exotic. It has been widely planted in Africa, Asia, Australia, the Middle East, New Zealand, western USA and Central and South America, in woodlots, shelterbelts and parks, and along roadsides, rivers and canals. World Agroforestry Centre (2002) report that it has been introduced and become naturalized in many subtropical and tropical countries.

This species is classified as potentially invasive by Binggeli (1999) and is registered as invasive in Florida and South Africa. Other species within its genus are also invasive and have been a source of serious environmental problems. The wide introduction of this species across many tropical and subtropical countries may constitute a risk for future invasive events.

The seeds are winged samaras and can be dispersed abiotically by wind or water. In Australia, the fruits of all species of Casuarina are a major food source for several species of parrots (Schodde et al., 1993) though there is no information on whether these birds disperse the seeds. Referring to Casuarinas in general, Snyder 1992 states that seeds may be transported by animals. C. cunninghamiana has been intentionally introduced into many subtropical and tropical countries.

C. cunninghamiana is closely related to C. glauca, which differs in having larger cones, 12-16 leaf-teeth, and generally coarser and subglaucous foliage. C. glauca tends to grow in estuarine locations, tidal reaches and brackish water. Natural hybrids occur between C. cunninghamiana and both C. glauca and C. cristata (Wilson and Johnson, 1989) and hybrids with C. glauca are quite common in cultivation (El-Lakany et al., 1990a).

C. cunninghamiana is generally a dominant species in riverbank vegetation over its natural range. Surrounding vegetation types are eucalypt open-forest, woodland and open-woodland together with melaleuca woodland. It is also found along watercourses in deciduous vine forest in inland northern areas, associated with Eucalyptus camaldulensis and gallery rain forest assemblages. C. cunninghamiana has no regular associates over its entire range, but in the southern coastal lowlands it may grow with Eucalyptus elata and further north with E. tereticornis, Tristania neriifolia, Lophostemon confertus, L. suaveolens, Tristanopsis laurina and Leptospermum sp. (Beadle, 1981). In its native range it is noted to be replaced by C. glauca if the water is more saline (World Agroforestry Centre, 2002). In South Africa, where it is invasive, this species colonizes riverbeds (Henderson, 2001).

GeneticsAccording to Merwin (1989) this species has a haploid chromosome number of x=9. Consistent with other wide-ranging species, C. cunninghamiana exhibits substantial inter- and intra- provenance variation, and therefore careful selection of the origin of planting stock is recommended. After 2 and 5 years, provenance trials in California, USA using mainly southern Australian seed origins indicated significant genetic variation in growth and survival both between and within provenances (Merwin, 1990; Merwin et al., 1996). Major differences in frost tolerance among provenances have been observed in these trials, with inland high-altitude provenances tolerating temperatures of -7 to -12ºC, while low-altitude coastal provenances were severely damaged or killed. In a range-wide trial of 18 provenances of subsp. cunninghamiana in Egypt, a clinal pattern of 7-year growth and survival from north to south was found (El-Lakany, 1990). A negative correlation between height growth (at 2.5 years) and latitude of provenance was also reported for this species in China (Pan and Lu, 1990). Variation in growth at 54 or 57 months between 10 natural provenances and a local landrace was reported at three sites in Costa Rica (Zamora et al., 1995).Patterns of variation reported from the field trials complement results of allozyme analysis by Moran et al. (1989) and Moore and Moran (1989). Allozyme analysis indicated a relatively high level of genetic diversity (26.4%) between populations from different river systems, and a contrasting low level of genetic variation among populations in a single-river drainage system. A latitudinal cline in genetic diversity, showing decreasing diversity with decreasing latitude, was documented for subsp. cunninghamiana. The allozyme data supported the taxonomic separation of subsp. miodon from subsp. cunninghamiana. Physiology and PhenologyC. cunninghamiana is a long-lived, moderately fast growing tree. As with all species in the genus, it does not develop resting buds and grows whenever conditions are favourable. Age to first flowering in this species was 16-29 months in trials in southeastern Queensland, Australia (Ryan and Bell, 1989). Peak flowering is usually in autumn but the species may flower at any time from March to October, depending on season and locality (Clemson, 1985; Blake and Roff, 1988). Individual male trees of C. cunninghamiana flower once a year. Male anthesis usually takes place over 2-10 days, and peak pollen production varies among trees within a population. Boland et al. (1996) noted that some trees of this species may have a second minor flowering peak in the same flowering season, if the first flowering is cut short by cooler weather. In this case, anthesis may be extended over 30 days. Individual female trees flower once a year, but vary in their peak flowering periods. Boland et al. (1996) observed that older trees in natural stands were more precise in their flowering times than young cultivated trees, some of which bore receptive female cones throughout the year. Single inflorescences may flower over a long period, with receptivity noted over 20-30 days for late-season inflorescences (Boland et al., 1996).After about 12 months of growth following fertilization, the cones slowly change colour from green to brown and may stay on the tree in a fully mature state for a further six months (Boland et al., 1996). Seed from northern populations may be collected from February to March, and from southern areas in April/May. In Canberra, Australia (latitude 35.3°S, altitude 600 m) natural seed shed commences late winter to early spring (August-September), and most of the old crop is shed by November (i.e. approximately 20 months after anthesis; Boland et al., 1996). It is unusual in this species to have two seed crops from different seasons on the one tree at the same time. El-Lakany et al. (1990a) observed that there were an average of 32 samaras per cone in C. cunninghamiana grown in Egypt. Merwin (1989) reports that the C. cunninghamiana roots are particularly efficient at collecting and absorbing nutrients (e.g. nitrogen, phosphorus and calcium).Reproductive BiologyA review of the reproductive behaviour of C. cunninghamiana is provided by Boland et al. (1996). Like most of the casuarinas it is wind pollinated. The species is mostly dioecious with individuals bearing unisex flowers in an approximate 1:1 mix of both sexes, but monoecious individuals exist (Boland et al., 1996). Peak flowering is usually in autumn but the species may flower at any time from March to October, depending on season and locality (Clemson, 1985; Blake and Roff, 1988). After about 12 months of growth following fertilization, the cones slowly change colour from green to brown and may stay on the tree in a fully mature state for a further six months (Boland et al., 1996). It is unusual in this species to have two seed crops from different seasons on the one tree at the same time. The seeds are winged samaras and are relatively small in comparison with other Casuarina species, i.e. the weight of 1000 seeds is 0.56-0.57g (Turnbull and Martensz, 1982; El-Lakany et al., 1990a). Seed production is prolific (on average 607,200 viable seeds/kg; Doran and Turnbull, 1997) and germination occurs easily. Root suckers have been observed in Egypt (El-Lakany, 1983a), but this characteristic is far less evident than in C. glauca (Boland et al., 1996). Environmental RequirementsIn Australia, C. cunninghamiana is found mainly in the warm sub-humid climatic zone. Some coastal localities are in the warm humid zone, while further inland some populations are in the warm semi-arid zone. In its natural range, the mean maximum temperature of the hottest month is 25-40°C, and the mean minimum of the coldest month is 0-15°C. In the hotter parts of its natural distribution, temperatures exceed 32°C for up to 100 days per year, and are over 38°C on 1-10 days. Populations at higher altitudes in New South Wales tolerate up to 50 frosts each year, and temperatures as low as -8°C. C. cunninghamiana has been successfully planted in regions with a mean minimum temperature in the coldest month of -2 to 19°C (Marcar et al., 1995). The annual rainfall is 360-2200 mm a year. Rainfall alone is no indication of the moisture available to the tree since the species is found in riverine habitats. Seasonal distribution of rainfall is more or less uniform for southern coastal localities in Australia, but for northern areas it changes to a moderate summer maximum, becoming monsoonal in the extreme north during December to March.C. cunninghamiana fixes atmospheric nitrogen, and is adaptable to a wide range of edaphic conditions in cultivation, including drought, periodic waterlogging, acid to moderately alkaline sandy to clay soils, and sites of moderate salinity. In Australia, C. cunninghamiana is restricted to rivers, stream banks and adjacent valley flats. It may extend for a short distance up rocky hillsides above watercourses. Surrounding topography varies from tablelands, dissected sandstone plateau, hills and lower slopes to coastal lowlands and alluvial plains. The soils are mainly sands or sandy loams, but include clayey loams and gravel terraces of old river courses. The species has also been infrequently recorded growing on clays. The soils are mainly acidic or near neutral. C. cunninghamiana is only moderately tolerant of saline conditions and, under natural conditions, is usually replaced by C. glauca where the water becomes brackish in coastal rivers. It also becomes chlorotic on highly calcareous soils (Weinstein, 1983).AssociationsIn its native Australia, C. cunninghamiana is found along watercourses in deciduous vine forest in inland northern areas, associated with Eucalyptus camaldulensis and gallery rain forest assemblages. C. cunninghamiana has no regular associates over its entire range, but in the southern coastal lowlands it may grow with Eucalyptus elata and further north with E. tereticornis, Tristania neriifolia, Lophostemon confertus, L. suaveolens, Tristanopsis laurina and Leptospermum sp. (Beadle, 1981).A useful synergism exists between C. cunninghamiana and Euseius addoensis addoenis, a predacious mite and important predator of thrips and mites on citrus in the eastern Cape Province of South Africa (Grout and Richards, 1992). Euseius addoensis addoenis can survive and reproduce on Casuarina pollen, which may help maintain predacious mite populations during the autumn when natural sources of prey are diminishing.Roots of C. cunninghamiana form symbiotic partnerships with soil microorganisms, such as Frankia (a nitrogen-fixing actinomycete) and mycorrhizal fungi. According to many previous reports, the symbiosis with Frankia provides nitrogen to the host plant and assists Casuarina spp. to grow on low fertility soils (e.g. Midgley et al., 1983; El-Lakany et al., 1990b; Pinyopusarerk et al., 1996). Increasingly, evidence indicates that the availability of salt-tolerant Frankia plays an important role in establishment of Casuarina spp. on salt-affected land (Marcar, 1996). However, Casuarina spp. introduced into exotic localities are commonly unnodulated due to a lack of native Frankia, such as in New Zealand (Bulloch, 1994) and Sudan (Miettinen et al., 1992). Studies have shown that the effectiveness of the Casuarina-Frankia symbiotic relationship is strongly influenced by the availability of certain nutrients from the soil to the host plant. The availability of phosphorus appears to be especially important (Reddell et al., 1986). One means a host plant has of obtaining phosphorus is through the symbiosis of its roots with mycorrhizal fungi. Vesicular arbuscular mycorrhiza (VAM) associations are the most common in Casuarina, including C. cunninghamiana (Reddell et al., 1986; Khan, 1993). However, ectomycorrhizal associations also occur in this genus (Brundrett et al., 1996).

In China, seven diseases have been identified affecting Casuarina plantations (Bai and Zhong, 1996). The most serious of these is bacterial wilt disease, Pseudomonas solanacearum. This is a serious disease of 2-15-year-old trees, affecting roots, branches and stems of 10-100% of trees, depending on location, and causing losses in yield of 10-50% (Zhong, 1990). No effective control measures have been found. Casuarina roots are also susceptible to infection by nematodes (El-Lakany, 1983a).Chalcidoid wasps (Bootanelleus sp., Torymidae) destroy seed in the fruits of C. cunninghamiana (Andersen and New, 1987) in Australia. A serious dieback problem of C. cunninghamiana exists in southeastern Queensland, caused by the repeated defoliation by the leaf-eating chrysomelid beetle, Rhyparida limbatipennis. This has been linked to declining site quality caused by poor management on adjacent farmlands (Wylie et al., 1993). In China, 81 insect species causing mostly only light damage to casuarinas have been identified (Bai and Zhong, 1996). In Egypt, young trees of C. cunninghamiana are mainly free of serious pests. However, trees over 14-15 years old are vulnerable to attack by many wood-destroying insects, including the dry wood termite Kalotermes flavicollis and the coleopteran pests Stromatium fulvum and Macrotoma palmata (Hassan, 1990).In Australia, the fruits of all species of Casuarina are a major food source for several species of parrots (Schodde et al., 1993); and severe damage to C. cunninghamiana has been caused by crimson rosellas in the Canberra region of Australia (Boland et al., 1996). Young seedlings are the targets of pests such as hares and rabbits, and foliage is very attractive to livestock.

The control of Casuarina is costly.

Referring to Casuarina species collectively, Snyder (1992) reports that their dense roots are able to reduce soil moisture and damage drains.

The flowers have an irritant effect on the respiratory tract (Henderson, 2001).

The habit of C. cunninghamiana makes it suitable for ornamental use, for shelterbelts providing wind protection for crops and animals, and for riverbank stabilization. In Egypt, it is an important species used to prevent sand from clogging irrigation channels (El-Lakany, 1983a) and is also suitable for sand dune stabilization (Kosmer, 1975). It is an important agroforestry species in China (Cao and Xu, 1990). C. cunninghamiana showed potential in agroforestry trials in Uganda, results indicating that the negative influence of the trees on adjacent crops might be minimized by periodic pruning of crowns and roots (Okorio et al., 1994). It is also under trial in an agroforestry system in southeastern Queensland (Dunn et al., 1994a). In New Zealand, South Africa and California, USA, C. cunninghamiana has proven particularly valuable for planting as windbreaks to protect high-value horticultural crops (Holmes and Farrell, 1993; Bulloch, 1994; Holmes and Koekemoer, 1994; Merwin et al., 1996). Sapwood is narrow and pale, with dark reddish or purplish-brown heartwood. In Australia, the wood is typically moderately strong, tough, fissile, fine-textured, straight-grained and with wide medullary rays. It is hard to work and dress but takes a good polish (Keating and Bolza, 1982; Bootle, 1983). The heartwood is extremely refractory to preservative treatment, but it is durable and may last for 15-25 years in the ground (Keating and Bolza, 1982). It has been used for casks, axe handles and ornamental turnery, as well as a general utility farm timber. In Egypt, particleboard is made from wood of C. cunninghamiana (El-Osta and Megahed, 1990), and in Argentina it is recommended for use in parquet flooring, packing cases, veneer, and barrel staves (Mendonza, 1983). C. cunninghamiana produces an excellent fuelwood which was once favoured for firing bread ovens in Australia. Young trees are grazed by livestock, and the foliage is useful as drought fodder, although not of high nutritive value. Craft dyers in Australia have used the foliage to produce attractive colours in wool using various mordants (Cribb and Cribb, 1981). The species provides valuable supplies of pollen for apiculture (Clemson, 1985; Blake and Roff, 1988).

C. cunninghamiana is relatively fire-sensitive, especially when young. Fires have been used to control the related C. equisetifolia when trees occur in high density and the location permits (Weber, 2003). Merwin (1989) reports that since one of the primary routes of spread in Florida, USA was along watercourses, one way of preventing invasiveness is to avoid planting the species along riparian corridors. In relation to Casuarina spp. as a group, Elfers (1988) specified that disturbance of natural habitats should be minimized to reduce opportunities for colonization and where habitats had to be disturbed, swift replanting with indigenous vegetation was recommended. An alternative cultural approach was to counteract potential invasion by periodic flooding (Elfers, 1988).Weber (2003) reports that the related species C. equisetifolia can be controlled mechanically by pulling up seedlings and saplings manually, and adults can be sprayed with triclopyr applied to a band at the bottom of the stem. Elfers (1988) summarized control information for the Casuarinas as a group (i.e. C. cunninghamiana, C. equisetifolia, C. glauca) citing common methods of control to include basal bark, squirt and hack, or cut stump application or injection of a triclopyr - diesel mixture.

C. cunninghamiana subsp. cunninghamiana is the better known of the two subspecies and the following details refer almost solely to this taxon. Subsp. miodon was formally described in 1989, and seed has been difficult to obtain, even in small amounts for species and provenance trials.C. cunninghamiana is a long-lived, relatively fast-growing tree. It is moderately drought resistant. For example, in Israel it grows best in the Mediterranean region, with a mean annual rainfall of 420-650 mm (Weinstein, 1983). It will only thrive in harsher conditions if some additional groundwater is available to supplement rainfall (e.g. Weinstein, 1993).It is relatively fire-sensitive, especially when young. Root suckers have been observed in Egypt (El-Lakany, 1983a), but this characteristic is far less evident than in C. glauca (Boland et al., 1996). It displayed fair to good coppicing ability in trials in southeastern Queensland (Australia) when harvested at a young age (18-41 months; Ryan and Bell, 1989) and tropical provenances coppiced strongly in trials in Thailand (K. Pinyopusarerk, CSIRO Forestry and Forest Products, PO Box E4008, Kingston ACT 2604, Australia, personal communication, 1997).Marcar et al. (1995) classified C. cunninghamiana as moderately tolerant of sodicity (pH of 8-9), and moderately salt tolerant (with reduced growth at electrical conductivity approximately 5-10 dS/m, and reduced survival above 10 dS/m). It may also withstand periodic waterlogging, including under low to moderate levels of salinity and sodicity. C. cunninghamiana is one of the best performing species under conditions of salinity, sodicity and waterlogging in the irrigated plains of the provinces of Punjab and Sind, Pakistan (Hafeez, 1993). However, it was less successful on low salinity but moderate to highly sodic soils at Peshawar (Hussain and Gul, 1991). It had good survival and growth under conditions of low to moderate salinity in tropical northern Australia, but was deemed less successful than Eucalyptus camaldulensis for rehabilitation on these sites due to its shallow root system and lower water use (Sun and Dickinson, 1995a, 1995b). It was rated as moderately salt tolerant (survival declined by 25% compared to control at electrical conductivity of 10-15 dS/m) on a saline site in southeastern Queensland (Dunn et al., 1994b). Marcar (1996) provides a review of the performance, physiology, genetic variation and interactions with Frankia for C. cunninghamiana and several other casuarinas that can be planted on salt-affected land.

The winged 'samara' (seed) of C. cunninghamiana is extracted by air-drying mature (brown) fruit until the bracteoles open; the seed is obtained by shaking and sieving. It is relatively small in comparison with other casuarinas: the weight of 1000 seeds is 0.56-0.57 g (Turnbull and Martensz, 1982; (El-Lakany et al., 1990a). In Egypt, germination rate varied according to season of harvest, an autumn harvest produced 52% germination and a spring collection 34% (El-Lakany et al., 1990a). Mature seed is classified as orthodox, and is fairly robust in storage. The germination capacity of seedlots stored in paper bags at room temperature for 0, 8 and 20 months was compared in trials in Egypt (El-Lakany et al., 1990a). There was no significant reduction in germination capacity over 8 months of storage, but by 20 months the proportion of germinating seeds had decreased from 59% to 35%. Seed moisture content over this time had increased from 6.3% when fresh to 8%. Storage of C. cunninghamiana seed in sealed containers at low temperature (approximately 5°C) was recommended.Vegetative propagation by stem cuttings, maintained on a mist bench and heated from below, has been successful (Pryor, 1989). Better strike rates and vigour of cuttings is achieved by using shoots growing close to the base of the tree (Pryor, 1989). In male trees this would be from permanent shoots bearing juvenile deciduous branchlets (Boland et al., 1996). Treatment of cuttings with root-inducing hormone powder has improved the success rate (Torrey, 1983). Vegetative propagation of C. cunninghamiana by air layering has been successfully applied in Thailand, while crown tip grafts and bottle grafts have succeeded in Australia (Pryor, 1989). In China, 70-80% of casuarina planting stock is currently produced as rooted cuttings, which are gathered from plus-tree clonal collection nurseries (Bai and Zhong, 1996).Despite the trend in China towards vegetative (cuttings) propagation, most planting stock is produced from seed, since seed production is so prolific and germination occurs easily. There is an average of 607,200 viable seeds/kg (Doran and Turnbull, 1997). Seed can be sown directly into containers or into germination trays. It should be sown under shade on a free-draining, sterilized medium and covered very sparingly with inert material, such as sand; optimum temperature for germination is 30ºC (Turnbull and Martensz, 1982). Germination should be complete in fourteen days, after which the shade may be reduced. At 4-6 weeks, when seedlings are 2-4 cm tall, germinants are transplanted from germination trays to containers filled with sterilized potting mix. Shade cover is needed for the first week after transplanting, after which time plants should be fully exposed to direct sunlight. Plants should reach plantable size (approximately 30 cm) in 3-6 months. Methods suitable for propagating casuarinas from seed are described by Carter (1987), Doran (1990) and Doran and Turnbull (1997). Bai and Zhong (1996) briefly describe methods used in China.C. cunninghamiana is used for many purposes, such as industrial plantations, woodlots, windbreaks, shelterbelts, riverbank stabilization and amenity. Therefore, the silvicultural system adopted will depend very much on the end-use of the planting. In China, the species is established in plantations at a spacing of 2 x 2 m. No thinning is applied and the plantations are clearfelled at 10-15 years (Bai and Zhong, 1996). Regeneration is by replanting within 1-2 years of harvesting. In Victoria (Australia), woodlot plantings into pasture at a spacing of 6 x 8 m with form and clearwood pruning applied as required are showing promise (Hall and Lyons, 1993).In southern Australia, C. cunninghamiana is most successful when planted into friable soil which has been deep ripped. The best time for planting out in this temperate environment is usually early spring, especially in the wetter areas, and deep planting (burying 30% of the stem in the ground) improves stability and increases tolerance to early dry conditions (Hall and Lyons, 1993; Bird and Stackpole, 1993). In southern China, red earth soils are ploughed and planting holes of 40 x 40 cm and 50 cm deep prepared before planting. However, sandy soils do not require ploughing, and the planting holes are smaller at 25 x 25 x 40 cm (Bai and Zhong, 1996).In many situations, fertilizers are not applied when artificially growing casuarinas. In China it is has been shown that phosphorus, nitrogen and some micronutrients (boron, cobalt, molybdenum and zinc) increase the productivity of casuarina plantations, especially on sandy soils. However, application of these nutrients depends on the financial position of tree growers (Bai and Zhong, 1996). On sandy sites, application of 100-150 g super-phosphate per tree, or 50-100 g of complete fertilizer 10 days after planting is recommended, with 1-3 follow-up applications of urea or complete fertilizer in the first 3 years after planting (Bai and Zhong, 1996).In semi-arid environments it may be necessary to irrigate plantations of C. cunninghamiana to obtain reasonable establishment and growth rates (e.g. in Egypt, Stewart et al., 1993). A study of the effect of irrigation with sprinkler or drip (trickle) systems on root characteristics of trial plantations of C. cunninghamiana in Egypt concluded that both methods of irrigation are satisfactory for this species (El-Lakany and Mohamed, 1993). C. cunninghamiana is moderately tolerant of salinity and sodicity. In waterlogged conditions, it requires appropriate site preparation, planting methods and post-planting maintenance to succeed (Marcar, 1996). The following techniques may aid survival in such conditions: mechanical ripping of the site to break up hard pans, use of saucer pits and furrows as 'water harvesting' techniques, planting on mounds in waterlogged areas, provision of subsurface drainage, use of soil mulching and addition of appropriate fertilizers (Marcar, 1996).C. cunninghamiana suffers from weed competition, and high losses may occur if weed-control is poor (Hall and Lyons, 1993). In plantations, lift and form pruning may be required to produce high quality timber (Hall and Lyons, 1993).Symbiotic associationsRoots of C. cunninghamiana form symbiotic partnerships with soil microorganisms, such as Frankia (a nitrogen-fixing actinomycete) and mycorrhizal fungi. According to many previous reports, the symbiosis with Frankia provides nitrogen to the host plant and assists casuarina to grow on low fertility soils (e.g. papers in Midgley et al., 1983; El-Lakany et al., 1990b; Pinyopusarerk et al., 1996). Increasingly, evidence indicates that the availability of salt-tolerant Frankia plays an important role in establishment of casuarinas on salt-affected land (Marcar, 1996). However, casuarinas introduced into exotic localities are commonly unnodulated due to a lack of native Frankia, such as in New Zealand (Bulloch, 1994) and Sudan (Miettinen et al., 1992). Inoculation of the seedlings with effective strains of Frankia is recommended when the species is introduced to a new area, as this may significantly increase seedling establishment and early growth rate. Bulloch (1994) reported on a trial in New Zealand using C. cunninghamiana: after 6-8 years, trees nodulated at planting were more vigorous and significantly larger in stem diameter and height (equivalent to 16-61% additional volume) than trees not nodulated at planting. Considerable variation exists in effectiveness of different Frankia strains (Coyne, 1983; Fleming et al., 1988; Reddell, 1990; Dommergues et al., 1990; Mansour and Baker, 1994; Masuka and Makoni, 1995; Reddell et al., 1988; 1996a). For example, Reddell et al. (1988) reported on a field trial in Zimbabwe of seedlings of C. cunninghamiana inoculated with liquid homogenized whole cell cultures of several Frankia strains. Fourteen months after planting into nitrogen-deficient soils, trees inoculated with three Frankia strains grew 50-70% higher than plants without inoculation treatment. Results using a fourth Frankia strain (ORS 020607) showed a tree growth rate three times higher than that of the uninoculated controls, and nearly double that of other 'Frankia-assisted' trees.Inoculation of seedlings with selected pure cultures of effective strains of Frankia is done by applying a water suspension of the inoculant to the seedlings. A less ideal method is to apply a solution of crushed nodules collected from the host species, preferably at the original site of seed collection (Midgley et al., 1983; El-Lakany et al., 1990b). Recent work has shown that peat- and alginate bead-based Frankia inoculants are both effective methods for inoculation of casuarinas in nurseries (Reddell et al., 1996b). Reddell et al. (1996b) indicate that the short supply of reliable, cost-effective Frankia inoculant is the major constraint to a wider application of more advanced inoculation techniques. Rouvier et al. (1996) showed there is genetic diversity among Frankia strains which infect members of the family Casuarinaceae. These latter results are contrary to previous molecular studies of isolated strains of Frankia, which showed a high level of homogeneity.Studies have shown that the effectiveness of the Casuarina-Frankia symbiotic relationship is strongly influenced by the availability of certain nutrients from the soil to the host plant. The availability of phosphorus appears to be especially important (Reddell et al., 1986). Trials have shown that phosphorus fertilization substantially increases the growth of C. cunninghamiana inoculated with Frankia (Reddell, 1990; Yang, 1995). Other macro- and micronutrients which appear to influence growth include calcium, cobalt, molybdenum and magnesium (Hewitt and Bond 1961; 1966; Kang, 1996). One means a host plant has of obtaining phosphorus is through the symbiosis of its roots with mycorrhizal fungi. Vesicular arbuscular mycorrhiza (VAM) associations are the most common in Casuarina, including C. cunninghamiana (Reddell et al., 1986; Khan, 1993). However, ectomycorrhizal associations also occur in this genus (Brundrett et al., 1996). Many exotic plantations are devoid of mycorrhizal associations since compatible fungi are not always present in the soil. Nurseries growing casuarinas, especially where the soils are deficient in phosphorus, are recommended to introduce appropriate mycorrhizas to the soil. Various inoculation systems, including soil, spores, sporocarps and vegetative mycelium, are described by Brundrett et al. (1996) and Doran and Turnbull (1997). C. cunninghamiana may also form cluster roots, and this may be another adaptive mechanism to optimize the acquisition of insoluble nutrients which are required for growth and nitrogen fixation (Khan, 1993; Diem and Arahou, 1996).

A number of studies have been conducted on growth and biomass production of C. cunninghamiana. Most reports indicate an annual growth of 1-2 m in height during the first few years (El-Lakany et al., 1990b). It is regarded as fast-growing under suitable conditions in South Africa, where it has a mean annual growth increment of 1.2-1.5 m in the first 10 years (Poynton, 1972). In Zimbabwe, C. cunninghamiana averaged 3.9 m tall and 5.4 cm in diameter, 30 months after planting (Gwaze and Stewart, 1990). In Uganda annual height growth ranged from 1.8 to 2.4 m (Okorio et al., 1994). In semi-arid areas of southern Ethiopia, C cunninghamiana has given satisfactory performance, reaching an average of 6.5 m in height and 8 cm d.b.h. in five years (Abebe, 1994). In Argentina it has reached 22 m after 24 years growth (Marlats, 1972). A 19-year-old plantation had a mean annual increment of 20.4 cubic metres/ha; in comparison, 4-year-old plants in an irrigation ditch measured 9.9 m tall and 13.9 cm in diameter (Mendonza, 1983). Egyptian data indicate a biomass production of 268 tonnes total dry weight (295 cubic metres of wood and 34 t of green foliage) in a 12-year-old stand (El-Osta and Megahed, 1990). Maximum volume increment is reached in 6-12 years, and harvesting at 18 years old is recommended (Badran and Tawfik, 1971).

Seedlings require protection from browsing stock and fire in initial stages of growth. C. cunninghamiana is not as tolerant of saline and calcareous soils as C. glauca or C. equisetifolia. Its utilization as sawnwood is limited by its tendency to warp, twist and split during seasoning.