Dactyladenia barteri (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Dactyladenia barteri (Hook.f. ex Oliver) G.T. Prance & F. White

Protologue: Brittonia 31: 484 (1979).

Family: Chrysobalanaceae

Chromosome number: 2n= 22

Synonyms

• Griffonia barteri Hook.f. ex Oliver (1871),
• Acioa barteri (Hook.f. ex Oliver) Engler (1899).

Vernacular names

• Monkey fruit (En).

Origin and geographic distribution

Dactyladenia barteri is endemic to West and Central Africa from Sierra Leone to Cameroon and Gabon. Its occurrence in Kivu in Zaire is uncertain.

Uses

D. barteri is widely used in south-eastern Nigeria as a fallow crop, producing large amounts of litter and recycling appreciable quantities of nutrients through its deep root system. The dense canopy also aids in weed suppression. In farmers' fields, it is either planted or protected in natural regrowth. Leaves are used for fodder. Stems provide good quality poles for staking crops and for construction work.

In Nigeria and Liberia the bark and roots are used medicinally as a purgative and against a variety of ailments.

Properties

The leaves of D. barteri grown on acidic sandy soil contain per 100 g oven-dry matter: N 1.7 g, P 0.08 g, K 0.77 g, Ca 0.57 g, Mg 0.25 g, Cu 1.2 mg, Zn 0.8 mg. The dark red wood of D. barteri is hard and durable and resistant to termite attack.

Botany

• Climbing shrub or small tree, up to 12 m tall; bole fluted, often multiple, crooked, up to 25(-40) cm in diameter; bark brittle, slash thin and watery-white, turning reddish; crown dense, spreading.
• Young shoots dark red, covered with whitish, arachnoid tomentum, early caducous; branches more or less scandent, slender, hispid, very quickly glabrescent when young, with numerous lenticels when old.
• Leaves alternate, simple; stipules often attached near the base of the petiole, linear, 4-6 mm long; petiole 3-4 mm long; blade elliptical-oblong to ovate, 7-13(-15) cm × 3-5.5(-7) cm, dark glossy green, turning reddish-brown when senescent, base acuminate, sometimes broadly acuminate and somewhat asymmetrical, apex acuminate; lateral veins in 4-6 pairs, some circular glands often present on the underside of the blade near the base and the apex.
• Inflorescence a terminal or axillary raceme, single or sometimes in pairs, 3-4(-12) cm long, puberulous, many flowered; peduncle up to 1(-4) cm long; bracts elliptical-lanceolate, 2-4 mm long, tricuspidate, often with circular glands; pedicel articulated, portion below articulation 6-10 mm long, long persistent, bearing 2 alternate, lanceolate bracteoles 1-1.5 mm long; upper portion 5-15 mm long.
• Flowers bisexual, zygomorphic; receptacle tubular, 4-6 mm long, puberulous; sepals 5, 4-5 mm long, puberulous outside; petals 5, oblong-obovoid, 4-5 mm long, white, caducous; stamens 15-20, (15-)25(-30) mm long, ligulately connate for most of their length, far exserted; pistil with 1-locular ovary, a filiform style slightly longer than the stamens, and a 3-lobed stigma.
• Fruit a single-seeded drupe, compressed-ovoid, 2.5 cm × 3.5 cm × 5.0 cm, green, surface often ferruginous-tomentose, apex often slightly tuberculate.
• Seedling with epigeal germination.

The root system is deep, but its lateral expansion in the top layer of the soil is limited. On an ultisol in south-eastern Nigeria, for instance, about 50% of the roots of less than 2 mm in diameter occurred in the top 20 cm of the soil near the stem, whereas at a distance of 120 cm from the tree base this percentage dropped sharply. In Nigeria and Ghana, D. barteri flowers usually during the dry season, between October and February. Fruits mature at the beginning of the rainy season, between March and May. D. barteri is open-pollinated, the main pollinators being red ants.

Ecology

D. barteri occurs in lowland forest up to 300 m altitude with at least 1200 mm rainfall per year, where the mean minimum temperature of the coldest month is about 20 °C and mean maximum temperature of the hottest month about 34 °C. In the forest-savanna transition zone, it is found along river banks, sometimes on the inland side of mangrove forest. It is well-adapted to leached, acid and infertile soils and can survive occasional flooding. Established trees are fire-resistant.

Agronomy

Propagation is mainly by seed. Occasionally, stakes are used as cuttings in live fence systems. Juvenile stem cuttings will also root quickly. Seed germinates readily. It can be stored for up to 6 months at 15 °C when treated with copper sulphate. Direct sowing is possible, but seedlings survive better when raised in nursery bags before planting out. In traditional cropping systems, D. barteri is retained, planted scattered, or in hedgerows. Established trees coppice well, even after pollarding or burning. In south-eastern Nigeria it is planted in hedgerows in a traditional alley cropping system with inter-hedgerow spacing of 2-3 m in fallow systems with 1-2 years of cropping followed by 3-4 years of fallow. Following the fallow period, the shrubs are underbrushed and burned and stems cut to a height of 10-20 cm. Some stems are left uncut for live staking of white yam (Dioscorea rotundata Poiret). Crops are then interplanted in the alleys.

Planted at 4 m × 4 m spacing, D. barteri can produce per ha 6 t dry prunings (leaves and small branches), 4 t twigs and 9 t wood within 8 months, with a nutrient yield of the prunings of 85 kg N, 5 kg P, 43 kg K, 18 kg Ca and 46 kg Mg. In an alley-cropping experiment, D. barteri planted in rows 4 m apart at a within-row spacing of 50 cm produced 3.5 t/ha oven-dry litter and 1.4 t/ha dry wood when pruned 22 months after planting. The nutrient content of the prunings was: 65 kg N, 6 kg P, 41 kg K, 33 kg Ca and 13 kg Mg. The prunings have a high C/N ratio (28:1 - 36:1), lignin (47.6%) and polyphenols (4.1%) content and decompose slowly in the soil, making good mulch material. The mulch has little direct effect on soil nitrogen. Nitrogen immobilization by decomposing D. barteri leaves is counteracted by increased mineralization of soil organic matter under the mulch. The decomposition rate of the mulch is very low. After 100 days as little as 20% may have decomposed, after 6 months about 50%.

Genetic resources and breeding

The genus Dactyladenia Welwitsch comprises about 27 species. It has been suggested that D. lehmbachii (Engl.) Prance & F. White and D. pallescens (Baill.) Prance & F. White, which flower in the same period, may cross-pollinate with D. barteri. There is potential for genetic improvement of D. barteri to enhance coppicing, growth and biomass yield.

Prospects

D. barteri has shown promise as a mulch and alley crop in experiments at the International Institute of Tropical Agriculture (IITA) in Nigeria. There is a need to evaluate its potential in other regions of the tropics with high rainfall and acid soils, in agroforestry systems to promote sustained crop production on highly weathered soils. Already in use at the IITA as a test tree in alley cropping systems on poor acid soils, it may contribute to the development of such systems in South-East Asia as well. Provenance evaluation and variability studies are needed to reveal the amount of exploitable genetic variation which may exist within D. barteri.

Literature

• Kang, B.T., Akinnifesi, F.K. & Pleysier, J.L., 1994. Effect of agroforestry woody species on earthworm activity and physicochemical properties of worm casts. Biology and Fertility of Soils 18: 193-199.
• Kang, B.T., Versteeg, M.N., Osiname, O. & Gichuru, M.P., 1991. Agroforestry in Africa's humid tropics: three success stories. Agroforestry Today 3: 4-6.
• Letouzey, R. & White, F., 1978. Chrysobalanaceae. In: Aubréville, A. & Leroy, J.F. (Editors): Flore du Cameroun. Vol. 20. Muséum National d'Histoire Naturelle, Paris, France. pp. 10-13.
• Hauser, S., 1993. Root distribution of Dactyladenia (Acioa) barteri and Senna (Cassia) siamea in alley cropping on ultisol. 1. Implication for field experimentation. Agroforestry Systems 24: 111-121.
• Kachaka, B., Vanlauwe, B. & Merckx, R., 1993. Decomposition and nitrogen mineralization of prunings of different quality. In: Mulongoy, K. & Merckx, R. (Editors): Soil organic matter dynamics and sustainability of tropical agriculture. John Wiley and Sons, Chichester, United Kingdom. pp. 199-208.
• Ruhigwa, B.A., Gichuru, M.P., Mambani, B. & Tariah, N.M., 1992. Root distribution of Acioa barteri, Alchornia cordifolia, Cassia siamea and Gmelina arborea in an acid ultisol. Agroforestry Systems 19: 67-78.
• Tian, G., Kang, B.T. & Brussaard, L., 1992. Biological effects of plant residues with contrasting chemical compositions under humid tropical conditions - decomposition and nutrient release. Soil Biology and Biochemistry 24: 1051-1060.

Authors

D.O. Ladipo & B.T. Kang