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2.5 Albizia lebbeck - a Promising Forage Tree for Semiarid Regions

J.B. Lowry, J.H. Prinsen and D.M. Burrows


Introduction
Nomenclature
Botanical Description
Distribution and Ecology
Productivity
Silviculture
Diseases and Pests
Animal Production Value
Other Uses
Allied Species of Interest
Conclusions
References


Introduction

Albizia lebbeck is a tree well known in the Indian subcontinent for its range of uses. Although geographically widespread, little is known about the species outside India. It appears to have potential for increasing pastoral production in extensive systems in the wet-dry tropics where the major problem is low feed quality of the basal diet, mature tropical grasses. Albizia lebbeck addresses this problem in three ways: as a feed, as a supplement and by improving grass quality.

Nomenclature

Albizia lebbeck (L.) Benth (Mimosaceae) has a variety of vernacular names including siris, koko, vagai (India), tekik (Javanese), kitoke, tarisi (Sundanese), khago, ka se (Thai), East Indian walnut and Indian siris (timber trade). A number of names are trivial (mother-in-law's tongue, rattle-pod (West Indies)) or misleading (acacia, raintree (northern Australia)). The Indian name siris is most commonly used (Anon. 1980). Use of 'albizia' as a common name should be avoided as it is often applied to Paraserianthes falcataria, a species of major importance in the wet tropics, and very different from siris. Albizia is a genus of about 100 species, very similar to Acacia but formally distinguished by the stamens being fused at the base rather than free. The genus is more restricted to the tropics than the acacias, and none of the species is phyllodinous.

Botanical Description

A medium to large tree, of multi-stemmed widely spreading habit (to 30 m diameter) when grown in the open, but capable of good log form in plantation. Height to 20 m. Bark rough, grey; inner bark reddish. Leaves bipinnate, rachis 70-90 mm, rachillae 1-5 pairs, 50-70 mm. Leaflets 3-11 pairs, oblong to elliptic-oblong, asymmetrical, 15-65 mm x 5-35 mm, glabrous, entire, initially bright green and folding at night, maturing to a duller glaucous green and fixed rachis. Fully but briefly deciduous in the dry season. Inflorescence an axillary cluster of 15-40 pedicellate flowers. Peduncle to 100 mm, pedicel 1.5-5 mm, corolla inconspicuous, free filaments numerous, 15-30 mm. Entire inflorescence, fluffy, 60 mm diameter, yellow-green with distinctive pleasant fragrance. Pod flat oblong 120-350 mm x 30-60 mm, stiff-papery when ripe, swollen over seeds, dehiscent. Seeds 3-12 per pod, brown, flattened, 7 x 1.5 mm (Figure 2.5.1).

Distribution and Ecology

Siris is indigenous to the Indian subcontinent, to those areas of southeast Asia with a marked dry season (e.g. northeast Thailand, eastern islands of Indonesia) and to the monsoon areas of northern Australia. In this latter region, it has been recorded in such formations as 'semi-deciduous mesophyll vine forest' (Kabay and Burbidge 1977). Herbarium notes often place it at the rainforest-eucalypt woodland ecotone. These indigenous populations are probably declining as seedlings cannot establish under continuous grazing by cattle. It has been distributed widely around the tropics, mainly as a shade tree, and has occasionally naturalised. It can grow well under a wide range of rainfall regimes (600-2,500 mm) yet can be seen in areas with only 400 mm. It may be established in areas of highly variable rainfall but in its natural habitat probably requires a reliable wet season. In the Himalayas it is found to 1,600 m altitude. It is found on a wide range of soil types including those that are alkaline and saline (Prinsen 1986) but not subject to waterlogging.

Siris seedlings will not tolerate frost. Reserves in the root system enable young plants to survive total defoliation from fire or grazing, but with obvious setback to growth. Growth is opportunistic when conditions are suitable but ceases for 2-3 months before leaf drop. Trees are leafless for only 4-6 weeks, with new leaf produced at the height of the dry season, followed in the tropics by a gregarious flowering. Flowers are insect-pollinated. Seed dispersal seems to occur mainly due to strong wind, when intact pods can be carried hundreds of metres. Seeds are retained in pods until they fall. Some seed passes through the intestinal tract of cattle but not of smaller ruminants.

Productivity

Comprehensive yield data have not been published. However, it is evident that the species is productive when actively growing or regenerating or as undisturbed mature trees. Under best conditions, plants can grow to 5 m in one year; however, growth in areas with under 800 mm annual rainfall is much slower.

Fig. 2.5.1. Leaves, flower and pod of Albizia lebbeck.

Fuelwood plantations produce 5 m3 ha/year (Anon. 1980). Isolated mature trees produce edible dry matter at the rate of 100-120 kg/year (Lowry 1989). Leaf litter fall under plantation conditions was 5,000 kg/ha/year (Pradhan and Dayal 1981). Wayside trees in the dry tropics show a crown diameter expansion of 22.2 m/year until mature (Lowry and Lowry 1991). Stands of mature trees with triennial pollarding yielded 1,700 kg/ha/year of edible material. Hedgerow stands browsed by cattle twice a year yielded 2,500 kg/ha/year in a subtropical low rainfall area where leucaena yielded 1,500 kg/ha/year (J.H. Prinsen, unpublished data). In Puerto Rico, plantings of 2,500, 10,000, and 40,000 trees/ha had leaf dry matter yields in the first 24 months of 1,710, 2,560 and 3,670 kg/ha respectively (Parrotta 1988).

Silviculture

Seeds are freely produced and are relatively large (7,000-8,000 seeds/kg). The species is not particularly hard-seeded and a proportion of seeds germinate immediately without any treatment, but for best results a 10 s immersion in boiling water is desirable. Siris is not Rhizobium specific and naturalised. forms are nearly always capable of producing an abundance of nodules. Plants can be sown directly, container grown, or raised in a massed seedbed and planted out as bare-rooted stumps (Anon. 1970).

Establishment is of course dependent on initial provision of water and protection from grass or weed competition, but there are few published data on this (Lowry 1991). Observations at a 725 mm annual rainfall site in southeast Queensland indicate that at least 3 years are required from planting to initial utilisation by cattle (D.M. Burrows, unpublished data).

Diseases and Pests

Establishment can be affected by attack on young plants by mice or rabbits, marsupials and domestic ruminants. Leaves are largely unaffected by insects, but young leaves may be subject to heavy predation by larvae of the grass yellow butterfly (Eurema hecoba). This appears to be a very short-lived effect. The most serious pests are bark-feeding larvae of longicorn beetles. These do not affect small stems and have little effect on large stems, but complete girdling can cause dieback in stems in the diameter range 40-100 mm. There is considerable variation in susceptibility of individual trees. Trees may be more susceptible under prolonged water stress. Recently a psyllid, probably of the genus Heteropsylla, was reported as seriously affecting seedlings in India (Hegde and Relwani 1988). The infestation was controlled by two applications of Nuvacron (0.05%) but not by Malathion.

Animal Production Value

Trees may adapt to a semiarid environment in two divergent ways that are very relevant to animal nutrition. Leaves may be long-lived, heavily cutinised, durable and sclerophyllous, as in the phyllodinous acacias, or they may, as with siris, be less lignified, short-lived and deciduous. The latter are of potentially higher feed value because of the lower lignified fibre content but may be protected from browsing by secondary compounds.

Leaves of siris are remarkably free of toxins and tannins, and low in soluble phenolic compounds. It is one of the very few tree legume species where the leaves are utilised by fruit bats (Lowry 1987). Rabbits have shown good growth performance when fed siris leaf comprising 50% of the diet (Lowry et al. 1992). Flowers contain no adverse constituents but pods contain saponins (Varshney et al. 1971) which may limit intake but appear to have no other adverse effect. Protein and neutral detergent fibre contents are as follows: green leaf, 16-23 and 41-35%; fallen leaf, 10 and 49%; fallen flower, 23 and 51%; pods, 19 and 55%. In vitro digestibility values for leaf have been reported in the range 45-70% and are usually around 50% for mature leaf. Results of feeding experiments are presented in Table 2.5.1. The overall conclusion is that the leaf is of high digestibility early in the season, or in regrowth after cutting, but of only moderate digestibility when mature although still of higher quality than mature grass. Young leaf tastes bitter and intake may be limited when offered as the whole diet. This does not affect its value as a supplement.

The fallen leaf has shown surprisingly high voluntary intakes by sheep, probably due to its rapid fragmentation. Schlink et al. (1991) showed that all fractions fed as supplements produced an increase in digestible dry matter intake of low quality basal diet. The effect was greater with the lower quality basal diet of black spear grass. Fallen flowers are an excellent feed. The pods are of particular interest as animal response was poor when fed alone but was positive when fed as a supplement to poor quality grass (Table 2.5.1).

There is a direct supplemental value of siris in extensive grazing systems. Leaves, flowers and pods drop sequentially during the dry season and can be utilised directly by grazing animals without any management effort being necessary. In mature trees, leaves, flowers and pods fall in comparable amounts (Lowry 1989). However the potential benefits have not yet been measured in grazing experiments.

Trees in pasture

One of the most interesting aspects of siris is that, in addition to providing feed directly, it appears to enhance pasture production and quality. Isolated siris trees in tropical woodlands frequently have a conspicuously greener sub-canopy area in which black spear grass (Heteropogon contortus), dominant in the open grassland, has been replaced by higher quality Panicum maximum. On one site in the dry tropics, dry matter yields under the trees were much higher (1,710 kg/ha) than between trees (753 kg/ha) during the early wet season (Lowry et al. 1988). Subsequent studies at the same site showed that grass quality was maintained under the trees for about 2 months longer into the dry season than in the surrounding area. Similar observations of a 'canopy effect' have been made in widely separated areas of coastal Queensland (Prinsen 1986, J.H. Wildin, unpublished data). The cause of this effect is thought to be related to improved soil moisture status in the surface litter layer of shaded soil which increases litter breakdown and mineralisation of organic matter (Wild et al. 1993). It appears that the tree provides a biological solution to the problem of pasture quality decline in the dry season.

Table 2.5.1. Results from feeding experiments with Albizia lebbeck.

(a) Fed as entire diet

Plant part

Animal

DM

DMD

DDMI

ND

Reference



(g/day)

(%)

(g/day)

(%)


Fresh green leaf

sheep

55.2

64

474

82

1

Dry green leaf

sheep

61.5

48

396

66

1

Fallen leaf

sheep

84.0

42

473

46

1

Fallen flower

sheep

71.5

57

546

70

1

Pod

sheep

20.4

44

120

71

1

Leaf

sheep

93.7

44

464

60

2

Leaf and 10% molasses

sheep

100.0

44

484

69

2

Leaf

goats

-

57


65

3

(b) Fed as supplement with mature spear grass (Heteropogon contortus)



DMI grass (g/day/kg W0.75)

DMI supplement (g/day)

DMD whole diet (%)

DDMI (g/day)


Control


29.5

0

30

141

4

Green leaf


31.7

6.3

38

229


Flower


33.6

6.3

38

241


Pods


28.4

6.3

39

215


Fallen leaf


26.3

6.3

34

171


(c) Fed as supplement with mature Mitchell grass (Astrebla squarrosa)

Control

34.6

0

43

138

5


Leaf

34.2

20.8

41

208



Flower

36.6

18.5

60

251



1. Lowry (1989); 2. Gupta (1981); 3. Murugan and Kathaperumal (1987); 4. Schlink et al. (1991); 5. Dwatmadji et al. (1992).
DMI = dry matter intake (g/day/kg W0.75); DMD = dry matter digestibility (%); ND = nitrogen digestibility (%);
DDMI = digestible dry matter intake (g/day)

Shading and animal production

Heat stress affects production of grazing animals in the dry tropics and the requirement for shade is well known although there are few quantitative data. Shading in northern Australian eucalypt dominated woodlands is typically diffuse. Light transmission through the canopy is about 80% even with a high population of trees, whereas transmission through the canopy of mature siris trees is 40-50%. Provision of such shade would itself benefit animal production.

The above considerations suggest a number of management options for incorporating siris trees in pastoral systems:

· grow trees intensively in rows or woodlots, as a protein supplement, for feeding weaners or as a drought reserve, lopping annually or as necessary,

· establish trees at low density in open woodland with no management once established, and

· develop agroforestry regimes in which animal production benefits are combined with wood production.

Other Uses

India has a well developed trade in siris for sawn timber. The heartwood is dense (specific gravity 0.55-0.60), easily worked and dark brown, with a very distinct boundary from pale sapwood. A range of uses as cabinet timber have been listed, including the doors of Chinese temples (Burkhill 1966).

More generally, it is useful as an amenity tree although the leaf, flower and pod fall that are valuable for animal production can become a litter problem. It is valued as a fuelwood species because of its high productivity (Anon. 1980). Calorific value of air-dried wood is 5,200 kcal/kg. It is also valued as a honey tree due to its production of both nectar and pollen.

A variety of traditional medicinal uses have been recorded (Dastur 1951). Bark extracts have documented anti-inflammatory activity (Tripathi et al. 1979).

Allied Species of Interest

In northern Australia siris is easily confused with A. canescens, although there is little problem with identification when either flowers and pods are examined. The latter species usually forms a smaller tree and appears to be palatable, but is uncommon in woodland under grazing.

Albizia procera (red siris) is a closely allied species that deserves further attention. It is accepted as a source of high quality timber in Australia (Hall et al. 1975). Although regarded as a rainforest species it can be found in woodland habitats well away from rainforest, and can have good form even as an isolated tree. Preliminary results (J.B. Lowry, unpublished data) suggest that the feeding value is similar to that of siris, and herbarium notes indicate it was regarded as a fodder tree by early settlers. This species appears an ideal candidate for a combined wood production and grazing regime.

Albizia basaltica (dead finish) is a shrub or small tree native to areas of central Queensland. The leaves are eaten by livestock, but are usually shed during the dry season (Everist 1986).

Conclusions

Albizia lebbeck has potential for use in silvopastoral systems with a number of benefits to graziers. Its foliage is of high quality for animals and the shade of its canopy is likely to benefit livestock directly, by reducing temperatures in hot environments, and indirectly by stimulating improved grass growth. Finally, the wood of Indian siris has value as a timber. Other species in the genus also show potential for exploitation and should be further investigated.

References

Anonymous (1970) Kokko (siris). Indian Timber Information Series No. 6. Forest Research Institute and Colleges, Dehra Dun, India, 3 pp.

Anonymous (1980) Firewood Crops: Shrub and Tree Species for Energy Production National Academy Press, Washington, DC, 235 pp.

Burkhill, I.H. (1966) Dictionary of Economic Products of the Malay Peninsula. Ministry of Agriculture and Cooperatives, Kuala Lumpur.

Dastur, J.F. (1951) Medicinal Plants of India and Pakistan. D.B. Taraporevala Sons & Co. Bombay.

Dwatmadji, Teleni, E., Bird, A.R. and Lowry, J.B. (1992) Nutritive value of Albizia lebbeck supplements for growing sheep. Australian Journal of Experimental Agriculture 32, 273-278.

Everist, S.L. (1986) Use of Fodder Trees and Shrubs. Queensland Department of Primary Industries, Information Series Q185015, Brisbane.

Gupta, B.S. (1981) Studies on the effect of molasses feeding on the nutritive value of siris (Albizia lebbeck) tree leaves. Indian Journal of Nutrition and Diet 18, 144-147.

Hall, N., Johnston, R.D. and Chippendale, G.M. (1975) Forest Trees of Australia. Australian Government Publishing Service, Canberra.

Hegde, N. and Relwani, L. (1988) Psyllids attack Albizia lebbeck in India. Nitrogen Fixing Tree Research Reports 6, 43-44.

Kabay, E.D. and Burbidge, A.A. (1977) A biological survey of the Drysdale River National Park, North Kimberley, Western Australia. Wildlife Research Bulletin Western Australia 6, 1-133.

Lowry, J.B. (1987) Green-leaf fractionation by fruit bats: is this feeding behaviour a unique nutritional strategy for herbivores? Australian Wildlife Research 16, 203-206.

Lowry J.B. (1989) Agronomy and forage quality of Albizia lebbeck in the semi-arid tropics. Tropical Grasslands 23, 84-91.

Lowry, J.B. (1991) Tree legumes: Albizia lebbeck. Research Notes, Division of Tropical Animal Production, CSIRO, Indooroopilly, Brisbane, 10 pp.

Lowry, J.B. and Lowry, J.B.C. (1991) Canopy growth of Albizia lebbeck in the semiarid tropics. Nitrogen Fixing Tree Research Reports 9, 92.

Lowry, J.B., Lowry, J.B.C. and Jones, R.J. (1988) Enhanced grass growth below canopy of Albizia lebbeck. Nitrogen Fixing Tree Research Reports 6, 45-46.

Lowry, J.B., Schlink, A.C. and Hoffman, D. (1992) Evaluation of three tropical legumes in diets for growing rabbits. Asian-Australasian Journal of Animal Science 5, 257-259.

Murugan, M. and Kathaperumal, V. (1987) Nutritive evaluation of vagai (Albizia lebbeck) leaves for goats. Indian Journal of Animal Nutrition 4, 61-62.

Parrotta, J.A. (1988) Early growth and yield of Albizia lebbeck at a coastal site in Puerto Rico. Nitrogen Fixing Tree Research Reports 6, 47-49.

Pradhan, I.P. and Dayal, R. (1981) Farm forestry in agricultural economy. Indian Forestry 107, 665-667.

Prinsen, J.H. (1986) Potential of Albizia lebbeck as a tropical fodder tree - a review of literature. Tropical Grasslands 29, 78-83.

Schlink, A.C., Lowry, J.B. and Gibson, D.S. (1991) Products from the tree legume Albizia lebbeck as supplements for sheep in the dry tropics. Proceedings of Australian Society of Animal Production 18, 546.

Tripathi, R.M., Sen, P.C. and Das, P.K. (1979) Further studies on the mechanism of the anti-anaphylactic action of Albizia lebbeck an Indian indigenous drug. Journal of Ethnopharmacology 1, 397-406.

Varshney, I.P., Badhwar, G., Khan, A.A. and Shrivastava, A. (1971) Study of saponins and sapogenins of Sesbania grandiflora seeds, Albizia lebbeck pods and Psidium guyava fruits. Indian Journal of Applied Chemistry 34, 214-216.

Wild, D.W.M., Wilson, J.R., Stür, W.W. and Shelton, H.M. (1993) Shading increases yield of nitrogen-limited tropical grasses. Proceedings of XVII International Grassland Congress. (In press.)


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