| Use of Trees by Livestock : Prosopis - Acacia - Gliricidia - Anti-Nutritive Factors - Quercus - Ficus - Calliandra - Erythrina |
|Use of Trees by Livestock : Erythrina|
Erythrina is a genus of some 108 species of shrubs and small to medium-sized trees (to about 20 m in height), which are often armed with blunt, conical thorns or sharp, recurved prickles which may occur on the trunks, young branches, petioles, leaf midribs and main veins. The leaves vary in shape, but are often deltoid or rhomboid. They are pinnately trifoliate and the terminal leaflet is often the largest. The lateral leaflets may be asymmetric. Erythrina spp. tend to shed their leaves under the influence of moisture stress, and where this happens the flowers often appear before, or with, the first new leaves at the start of the growing season. The flowers are usually red but may also be pink, orange or yellow. They are large and attractive, giving rise to the use of many species as ornamental plants. The seeds are commonly red to orange, or brown in colour, with a contrasting black (or sometimes white) patch at the point of attachment. They are carried, 2-14 at a time, in long, flattened or cylindrical, dehiscent pods with deep constrictions between the segments (Allen and Allen, 1981; Coates Palgrave, 1983).
Erythrina spp. occur over a wide range of natural habitats including open forest, dry brush and scrub, river banks, swamps and coastal regions. One species, E. tahitensis, is reported to occur at altitudes of up to 2900 m (Allen and Allen, 1981), and E. edulis is commonly found between 1800 and 2500 m. Maximum altitudes for E. fusca and E. poeppigiana are considered to be 1400 and 1700 m respectively, while E. tahitensis occurs naturally only at altitudes up to about 600 m. Those species which are adapted to higher altitudes show some frost tolerance, and most are susceptible to damage by fire (Coates Palgrave, 1983). In the Americas, species such as E. fusca are often found on the most acid and infertile of soils, and they thrive in waterlogged and poorly drained areas where fast-growing, nitrogen-fixing trees seldom prosper (Preston and Murgeitio, 1987). In Ethiopia, E. burana occurs in a range of situations, including shallow, swampy bogs and dry, rocky hills with slightly alkaline (pH 7.1-7.3), sandy or gravelly soils (Teketay, 1990).
Distribution of the genus is pantropical, with some 70 species found in the Americas, 32 in Africa, 18 in Asia and 3 in Australia and Argentina (Allen and Allen, 1981). See Krukoff and Barneby (1974) for a conspectus of the species.