|Casuarinas: Nitrogen-Fixing Trees for Adverse Sites (BOSTID, 1984, 114 p.)|
This chapter briefly mentions how various casuarinas are grown and used in almost 20 different regions. Although Australia has had the most extensive involvement with the trees, its experience is dealt with under the species themselves in chapters 6 and 7.
A new great wall has appeared in China - a green shelterbelt along the southern coast covering an area of more than 1 million hectares, built mainly with Casuarina equisetifolia.
In 1949, immediately after the People's Republic of China was established, the government made efforts to stimulate forestry development. People were mobilized and large afforestation projects started. These included forests primarily established for protection purposes, such as shelterbelts to stop the encroachment of coastal and desert sand dunes and to diminish the force of strong winds.
Since 1954, vast plantings of Casuarina equisetifolia have been established along the coast fronting the South China Sea. Much of the coast there comprises bare dunes that formerly were constantly moving inland, destroying arable land. This belt of casuarina stretches for 3,000 km and varies from 0.5 to 5 km in width. Most of it is in the province of Guangdong, but it extends into Fujian province and the Guanxi autonomous region.
The plantations grow in a mild, subtropical climate between the latitudes of 20°N and 30°N. Strong northeasterly winds occur frequently, and typhoons in summer are common.
Forestry officials in the area promote the use of casuarina. New plantations are planted using seeds collected selectively from trees that are tall, straight, fast growing and disease free.
Seedlings can reach 3 m tall 1 year after planting, and trees in an average plantation are 7-8 m tall and 5-7 cm in diameter after 4 years. The rotation period ranges from 10 to 15 years, and the mean annual increment averages 4-5 m3 per hectare.
The major benefits of this gigantic belt of Casuarina equisetifolia are the control of drifting sand, the sheltering of villages from coastal winds, and the production of wood for construction and fuel. The wood is used for house construction, especially for beams, as well as for boatbuilding and furniture. Fuel is a very important product for domestic use and for firing local brick kilns. In addition to branch wood and scrap wood that are used as fuel, each hectare of plantation annually provides up to 4 tons of litter and twigs that are continuously harvested for domestic fuel.
(In some areas the trees are attacked by a disease that causes the whole tree to wilt and die. This has been attributed to a bacterium, Pseudomonas, attacking the roots. Casuarina glauca is reportedly less susceptible.)
Casuarina equisetifolia (gago) is a common native tree in Guam and most other high islands of Micronesia where it grows both along the coasts and in upland savannas. On Guam the spread of the trees in savannas is retarded by frequent fires, which kill them. It occurs naturally on both limestone and volcanic soils.
PAPUA NEW GUINEA
Casuarinas are part of village life in the Highlands of Papua New Guinea. In the early 1950s the Department of Primary Industry (Office of Forests), together with various patrol officers, set up tree nurseries throughout the Highlands and people were taught the value of Casuarina oligodon and some other species. Since then the people have been growing casuarina, transforming the landscape from one predominantly of grasslands to an attractive and varied one with many trees.
In the early 1960s, as a small-scale research project, Casuarina oligodon was successfully underplanted beneath Araucaria hunsteinii and Araucaria cunninghamii. In recent years casuarinas have been used to revegetate copper mine spoil at Bougainville. And since before World War I, Casuarina equisetifolia has been an ornamental in Port Moresby, Wewak, Lae, Madang, Rabaul, and other coastal towns.
Casuarinas are also used as a cover crop for coffee. Coffee is a major cash crop in the Papua New Guinea Highlands, and Casuarina oligodon is a very useful shade tree because it lets light through to the crop and fixes nitrogen to improve the soil.
Casuarina equisetifolia is widespread in Thailand, and it has long been planted along coastlines to produce the poles used in building fishing traps as well as for fuelwood. A sterile hybrid between Casaurina junghuhniana and Casuarina equisetifolia was introduced to Thailand around 1900 as an ornamental tree. It soon received greater attention as a plantation species, owing to its fast growth, good stem form, and its adaptability to difficult site conditions. Both species are now used extensively to reclaim land abandoned after mining as well as for fuelwood production in village woodlots and for durable pilings for urban construction.
Casuarina equisetifolia was introduced into Madras State in the 1860s to fuel steam locomotives. Villagers then spread it along the coasts of the Indian Peninsula, especially on the east coast. In due course, farmers brought it into the South Indian agricultural system by planting it around their homes and fields. Casuarinas now provide protection to exposed sand on the shores of South India and on the Andaman Islands.
In South India Casuarina equisetifolia is considered the best species for colonizing sand dunes. In certain parts it is used to check dunes near farmers' fields, fishermen's dwellings, roads, railways, and ports. It makes life less wearisome in the coastal sands, with their fierce winds, flying sand, and dust under the hot tropical sun.
This tree is now one of the main firewood species in peninsular India. There are some 39,000 hectares under cultivation in plantations. Normally harvested on a 7- to 15-year rotation, the species yields 100-200 tons of fuelwood per hectare. The wood brings high prices. It is used for home cooking as well as for drying agricultural products such as cocoa, tea, copra, and tobacco.
Today, Casuarina equisetifolia is being planted on a large scale in parts of Tamil Nadu, where the dry season is 5-6 months long and the soil is coastal sand, river alluvium, red loam, red gravelly soil, or hard laterite.
In the 1970s the Casuarina junghuhniana x Casuarina equisetifolia hybrid was brought to India from Thailand as fuel for the tea-drying industry. This hybrid is performing well. There is also an unidentified casuarina species growing sparsely as shade trees in tea gardens in the Nilgiri Hills in Madras State. This species has not spread much.
In India, when casuarinas are felled they are converted and marketed in at least four forms: stumps, thicker branches, finer branches with needles, and billets 1 m long. These products meet the various needs of both the rich and poor. The stumps are exceptionally good for making charcoal.
In certain parts of India well-to-do agriculturists plant a few hectares to casuarina when their daughters are young. A 5-year rotation provides sufficient dowry at the time of the marriage settlement.
Casuarina equisetifolia is used with much success for binding sand near the seashore. The casuarina plantations are widespread along roadsides and as windbreaks and small woodlots. Casuarina plantations in Israel were found to be mixed stands of Casuarina cunninghamiana and Casuarina glauca, with the former comprising 75 percent or more of the trees. Growth of Casuarina glauca is superior to that of Casuarina cunninghamiana.
In addition, 15 Casuarina species are being tested in 16 experimental plots.
Casuarina is the most important genus of trees in Egyptian forestry. Three species are grown: Casuarina equisetifolia, Casuarina glauca, and Casuarina cunninghamiana. A natural hybrid between the last two species has also been identified.
Along the coast, Casuarina equisetifolia is planted to protect houses against wind and salt. Inland, desert highways are protected by belts of Casuarina glauca and Casuarina cunninghamiana. And when farmers receive land from the government, the first thing they do is to plant casuarina shelterbelts. The casuarinas' popularity in Egypt can be judged from the fact that annual planting was 1 million seedlings in the mid-1970s, 4 million in 1980, and is projected at 10-15 million by 1990.
Casuarina equisetifolia occurs along the Kenya Coast, often in sand dunes close to the sea. It has proved to be the best growing tree for reafforesting a formerly strip-mined limestone quarry of a cement factory near Mombasa. Approximately 40,000 trees were planted and vast numbers of seedlings are now colonizing the surrounding barren area. They are planted together with trees such as Conocarpus lancifolius and neem (Azadirachta indica). The estimated per hectare yield of wood is 120 tons and more in 5 years of growth. The charcoal and firewood produced from the casuarina is of superior quality. The straight stems are used for building poles and fence posts. (They must be treated to last if they are to be exposed to rain and high moisture.) The leaves are eaten by goats and eland. The humus under the trees rapidly increases as a result of the constant leaf fall. The dry leaves are eaten by the red-legged millipedes during the wet season, accelerating the process of humus production. In one part of the quarry 10 cm of humus has been produced in the last 10 years.
The trees are planted at 1 m x I m spacing, thinned out in the second and third year to 2.5 m x 2.5 m. The thinnings are sold for use in building mud-and-wattle houses.
Casuarina equisetifolia is also a popular amenity tree. About 10 years ago, establishment of the species started on plantation scale in Arabuka-Sokoke Forest Reserve. To date, there are about 350 hectares planted. The rate of growth is quite acceptable. In 9-year-old stands established at a spacing of 2.5 m x 2.5 m, the trees attained a mean height of 20 m and diameter of 12 cm. The wood is used mainly for building poles, fence posts, fuelwood, and charcoal.
Casuarina cunninghamiana and Casuarina glauca were introduced in 1908 and 1910, respectively. They are popular as ornamentals at an elevation of 1,600-1,800 m. Old trees of Casuarina cunninghamiana tend to be stag-headed.
Casuarina junghuhniana, introduced in 1956, has shown impressive performance. In a 26- year-old trial plot at an elevation of 2,100 m, trees have reached a mean dominant height of 25.5 m and diameter of 38.0 cm.
Casuarina torulosa was introduced in 1952. In a 30-year-old experimental plot on the same site as Casuarina junghuhniana, trees have reached a mean dominant height of 18.9 m and diameter of 29.6 cm.
Only one species, Casuarina equisetifolia, is successfully grown in coastal areas of Senegal. Introduced in 1925, it is now extensively used to stabilize coastal sand dunes between Dakar and St. Louis. These plantations now cover about 4,000 hectares and are being increased at the rate of 300-400 hectares per year.
The rainfall in the region is less than 500 mm annually. Brushwood, plastic fences, or fine nylon nets are first laid on the soil for temporary stabilization. Then, after rain has moistened the upper 40 cm of soil, the seedlings are planted. They receive no further attention.
Casuarina equisetifolia is the only plant yet found that can survive this harsh treatment in the very poor soils and hostile climate.
Casuarina cunninghamiana was probably introduced into Zimbabwe during the early years of this century, and since then it has been widely used for street and roadside plantings and windbreaks. Over the years the species has been largely neglected, but foresters now look at it with new interest. Agroforestry projects using it are being started, and researchers hope that it can help relieve Zimbabwe's acute fuelwood shortage.
In 1964-1965 two small plots of Casuarina junghuhniana were established in a high-rainfall locale from a seed sample obtained from Kenya. The health and general performance of these plots has been good. In 1982 seed of Casuarina decaisneana was sown in trials of trees for the country's arid areas.
Casuarinas, together with eucalypts and acacias, are common trees in Argentinean pampas and other dry areas of the country. To develop agriculture and livestock in these naturally treeless regions required the planting of trees for shade and to protect homesteads, animals, and crops from the strong, hot, and (in the north) salty winds. As a result, Casuarina cunninghamiana is very well known, although many people do not realize that it is not a pine.
In the Parana River delta, casuarinas are planted along the edges of rivers and creeks to protect the banks from erosion by waves. The intricate system of roots forms a strong wall against the water. The growth in these conditions is reported to be extraordinarily fast.
Casuarinas are now being planted around the huge saline Lake Texcoco in an effort to tame the dust storms that often overwhelm Mexico City.
Casuarinas are not common in Haiti, but a small plantation of Casuarina glauca has grown well on a severely eroded hillside. The stand, which has nitrogen-fixing nodules and root suckers, is proliferating over the stony soil surface, and litter buildup is protecting against further erosion. Casuarinas appear to be good candidates for restoring Haiti's eroded mountain soils and for providing the fuelwood, charcoal, and poles so desperately needed in that country.
In the dry zones of the Dominican Republic, and especially on alkaline soils, there are a few casuarina trees (thought to be Casuarina equisetifolia) that have grown to a large size. A private company has made trial plantings of Casuarina equisetifolia on reclaimed stripmined land in a humid zone and has found that it grows faster than Eucalyptus camaldulensis, Pinus caribaea var. hondurensis, and the native Pinus occidentalis.
Casuarina equisetifolia was a common street tree in the coastal city of Santo Domingo until hurricanes in 1979 blew the trees down. Trees 20-25 cm in diameter snapped off 3-5 m above ground, while larger trees were uprooted. Streets were clogged with debris from downed trees, and cleanup was costly. Casuarina equisetifolia is being replanted in some sections of the city, but it may not again become a common ornamental.
Because the Dominican Republic depends heavily on charcoal and wood for home cooking, and the native forests have been overexploited, casuarina plantations could become important to the fuelwood industry of the island.
In Puerto Rico, Casuarina equisetifolia is the only casuarina commonly planted. It is found along the coast and, less commonly, in the lower mountain regions. It is recommended for beaches and windbreaks. Planting close to buildings is discouraged because a disease sometimes kills old trees and there is danger that they will blow over in hurricanes. Natural regeneration is rare in Puerto Rico because ants eat nearly all the seeds.
In screening trials of trees for commercial timber production on granitic uplands, Casuarina equisetifolia grew faster than Pinus caribaea var. hondurensis and most other fast-growing species tried. Only Eucalyptus tereticornis outpaced it.
Various casuarina species, particularly Casuarina cunninghamiana and Casuarina stricta, have been used for street trees and ornamentals in California. They have also been planted along public highways and, along one particularly windy stretch of road in the San Francisco Bay delta, have proved superior to pine as a windbreak. Casuarina cunninghamiana windbreaks are being tested on croplands in several regions of the state, including high desert and inland valley sites, as part of a state-funded windbreak-demonstration program. It is also among the tree species recommended by the state forestry department for planting for fuelwood. Growth rates as high as 2 m in 6 months have been recorded for Casuarina cunninghamiana planted adjacent to irrigated and fertilized cropland. A number of species are also being tested on salt-affected soils in the southern San Joaquin Valley, including Casuarina decussata, Casuarina cristata, Casuarina glauca, and Casuarina helmsii.
Australian pines, as the casuarinas are known locally, are common on the Florida coast, as well as along roads and property lines, on ditch and canal banks, and around buildings. The identities of the different species are uncertain, but it appears that all trees are Casuarina equisetifolia, Casuarina glauca, Casuarina cunninghamiana, or their various hybrids. Once these trees were highly regarded for landscaping, windbreaks, and shade because they grow well on acid and alkaline soils, sand dunes, calcareous rocky soils, muck, and many other soils. Now Floridians are not so enthusiastic.
Casuarina wood has no economic use in Florida, and several problems are associated with the trees. On fore-shore dunes the roots can prevent sea turtles from digging nests for their eggs, and sometimes turtles are trapped by these roots. The casuarinas have crowded out native vegetation in some parts of coastal southern Florida. Much of the pollen is airborne from December to April and is suspected of being the cause of respiratory complaints during these months. Giant specimens along city streets threaten adjacent dwellings in this hurricane-prone region. As a result, some efforts are being made to eradicate the tree from environmentally critical areas, and landscape plantings that are being removed in the process of highway widening are not being replaced.
Casuarina equisetifolia is naturalized in southern Florida, and over many decades the land it occupies has slowly increased. Along the coast it is appreciated for its shade and the pleasant sound when the wind whispers through its foliage. The spread of Casuarina equisetifolia into the interior of southern Florida is limited by the frequent fires and severe freezes that periodically eliminate it there. It is out of control, however, on some sandy coastal habitats.
Casuarina glauca is also found as an ornamental windbreak and is used for cattle shade in southern Florida. On the coast it is usually found near brackish waters, but inland is where it is more prominent. Because of its prolific root suckering, it is now considered a pest: some counties have laws banning its planting and the planting of other casuarinas. While its root suckers create "mini-jungles" and its widespreading root system disrupts pavements and lawns, the scarcity of female trees in Florida fortunately restricts Casuarina glauca from getting entirely out of hand.
Casuarina cunninghamiana is less common in Florida, even though it is the most cold-hardy and the least objectionable. It is relatively slow growing and is intolerant of coastal sites.
Hawaii has perhaps tested more species of casuarina than any other location. Although there is estimated to be only 3,800 hectares of casuarina, 12 of the different species listed in this report are represensed.
In addition, there are plantings of Casuarina angularis, Casuarina nodiflora, and an unknown species from Timor.
Locally known as "ironwood," casuarinas have been planted for erosion control, dune stabilization, windbreaks, fuelwood plantations, beautification, and watershed cover. In the lowlands, the most extensively planted species has been Casuarina equisetifolia. In the uplands, Casuarina glauca has been most commonly used, primarily for erosion control.
Experience accumulated over the years suggests that in Hawaii casuarinas are best suited for elevations below 300 m, with annual rainfall of 500 1,000 mm. Elsewhere they cannot compete in growth rate with other species, especially on good sites. In high rainfall areas, most casuarina species have been slow starters and have ended up as understory trees in mixed planted stands. On the other hand, in low rainfall coastal sites casuarinas can and often do compete successfully with Prosopis and Leucaena, which are also fast-growing nitrogen fixers.
Casuarina equisetifolia is extensively planted in Portugal, Tunisia, Corsica, and other Mediterranean sites. It is also common in West Africa, for example Togo and Benin, where casuarina is systematically grown for charcoal in sandy coastal soils on a 10- to 12-year rotation.
Three species of casuarina occur in South Africa. Casuarina cunninghamiana, Casuarina equisetifolia, and Casuarina glauca grow rapidly and are hardy to both drought and frost. They are used for timber, poles, firewood, shelterbelts and windbreaks, and for reclamation.
Two species of casuarina occur naturally in Fiji. Casuarina equisetifolia (nokonoko) and Casuarina vitiense (velau) are both popular firewoods; velau is also utilized in construction where hardness and strength are required.