A.S. Bilaidi
A.S. BILAIDI is Head of the Forestry Section of the People's Democratic Republic of Yemen
Prior to 1965 a forestry service did not exist in the People's Democratic Republic of Yemen and the chief agents of introduction of exotics were the municipality of Aden, the British Army, the Ministry of Agriculture and individual plant lovers. During this period no accurate records were kept. The planting of exotics was limited to the municipal gardens of Aden and Sheikh Othman.
An attempt at introduction was made in 1965 when a British Forest Officer, S.F. Rawlins, was appointed for one year to carry out some limited activity resulting in seedlings later planted around the resident quarters of agricultural stations for shade and ornamental purposes. Mr. Rawlins filed a report on his activities at the end of his tenure.
Acacia tortilis found growing as far as the Empty Quarter
The present phase of forestry operations began in 1968, with the creation of a forest section as part of the Agricultural Research Station. Since then the section has developed intensively and the basic forestry foundations have been identified. The section is now managed by a selected team of national and international qualified foresters. The introduction, propagation and planting of exotics is being carried out on a large scale, mainly under irrigation, in the shape of wind barriers, roadside plantation, sand dune fixation and afforestation and general planting for protection and ornamental purposes around social and economic institutions all over the country. The Forestry Section keeps regular records of its various operations. Many are published by FAO and now a considerable literature is available for revision and documentation purposes country. The Forestry Section keeps regular records of its various operations. Many are published by FAO and now a considerable literature is available for revision and documentation purposes.
Table 1. - Statistical data on growth and yield for exotics planted as windbreaks in four state farms in the People's Democratic Republic of Yemen
|
Locality and date of planning |
Tree Species |
Mean height |
S1CV.2 |
Mean diameter |
S.1CV.2 |
Average volume |
|
Metres |
% |
Centimetres |
% |
Cubic metres |
||
|
Amgibla State Farm |
Azadirachta indica |
3.5 ± 0.8 |
2.28 |
7.4 ± 1.7 |
22.9 |
0.016 |
|
Eucalyptus camaldulensis |
7.09 ± 3.2 |
45.0 |
14.4 ± 3.9 |
27.0 |
0.129 |
|
|
Casuarina equisetifolia |
6.9 ± 1.6 |
23.2 |
9.4 ± 2.2 |
23.4 |
0.052 |
|
|
Conocarpus lancifolius |
3.6 ± 1.5 |
36.0 |
5.3 ± 1.8 |
33.9 |
0.011 |
|
|
Albizia lebbek |
4.1 ± 1.2 |
29.0 |
11.6 ± 3.9 |
33.6 |
0.051 |
|
|
26th Sept. State Farm |
Azadirachta indica |
4.5 ± 1.9 |
42.2 |
4.8 ± 1.4 |
29.0 |
0.011 |
|
Casuarina equisetifolia |
6.4 ± 1.8 |
28.12 |
6.4 ± 2.7 |
42.0 |
0.029 |
|
|
Conocarpus lancifolius |
7.5 ± 1.2 |
16.0 |
11.5 ± 2.7 |
23.8 |
0.076 |
|
|
Lenin State Farm |
Albizia lebbek |
10.7 ± 3.2 |
29.9 |
26 ± 7.2 |
27.6 |
0.658 |
|
Conocarpus lancifolius |
11.7 ± 3.4 |
29.0 |
15.3 ± 3.5 |
22.8 |
0.241 |
|
|
Eucalyptus camaldulensis |
15.13 ± 4.6 |
0.3 |
19.23 ± 3.1 |
16.1 |
0.468 |
|
|
6th Conference State Farm |
Albizia lebbek |
3.9 ± 1.7 |
43.5 |
3.9 ± 2.5 |
64.1 |
0.081 |
|
Prosopis cinerea |
5.2 ± 0.85 |
16.3 |
6.58 ± 3.7 |
56.2 |
0.023 |
|
|
Acacia mellifera |
1.5 ± 0.5 |
33.3 |
4.2 ± 0.9 |
37.5 |
3 |
|
|
Azadirachta indica |
2.8 ± 0.7 |
25.0 |
2.4 ± 0.9 |
37.5 |
0.003 |
|
|
Casuarina equisetifolia |
6.0 ± 1.4 |
23.3 |
3.9 ± 1.9 |
48.7 |
0.015 |
|
|
Conocarpus lancifolius |
5.3 ± 0.8 |
15.0 |
6.3 ± 1.4 |
22.2 |
0.017 |
|
|
Eucalyptus camaldulensis |
6.0 ± 1.8 |
30.0 |
5.1 ± 2.1 |
41.1 |
0.018 |
Notes: 1S. = Standard deviation. - 2CV. = Coefficient of variation. - 3Enumeration carried out in October 1976.
The first farm represents middle heights and the latter three represent coastal plains.
P.D.R. Yemen is a vast country, open to strong winds and shifting dunes which not only threaten agricultural lands but also menace communication lines, man and his livestock and social and economic development projects. The country faces a serious shortage of forestry products; and already large quantities of wood are being imported from abroad and must be paid for with foreign currency which is very much needed for other imports. Natural forest resources have greatly deteriorated as a result of adverse climatic and biotic factors and the absence, until recently, of a forestry service.
In areas where soil and moisture conditions are favourable, especially in the fertile wadi Deltas, the establishment of windbreaks, shelterbelts, and sand dune fixation and afforestation would provide besides protection, the most urgent need for the country's agricultural economy - substantial valuable amounts of timber, fuel and other intangible products. This can be achieved through the introduction of fast-growing exotics of high-yielding varieties and those which are most adaptable to the prevailing environmental conditions in the country. The statistical data on growth and yield for some selected species in four state farms of different soil, moisture conditions, and altitudinal ranges are presented in Table 1. In this Albizia lebbek and Eucalyptus camaldulensis attained the maximum height-diameter and volume growth under similar treatments. When planted in the Lenin State Farms in 1970, at 4 m and 6 m apart respectively, Eucalyptus camaldulensis produced 117 m3/km and Albizia lebbek 109 m3/km. One m3 of their timber sold at 7 and 10 Dinars, standing over bark, in the local market.
Three main nurseries in the country are managed by the forestry section. These are located in El-kod (coastal plains), Lodar (mid-altitude areas) and Hadramout (Hadramout plateau). They were established in 1968, 1972 and 1973 respectively, and are all engaged in production of seedlings from broad leaves except the Lodar Nursery which produces a small number of coniferous species for research purposes.
THE EFFECT OF BROWSING Maerua cassifolia
· Eucalyptus camaldulensis was introduced from Australia in early 1965. It was first planted at the El-kod Research farm together with 27 species of other Eucalyptus and selected later on for large-scale propagation. It grows straight with a good diameter height symmetricality. In incipient stages of growth it needs protection from the windward side in areas having strong winds. The horizontal crown diameter ranges from 1.75 ± 0.33 m to 1.92 ± 0.36 m after the first year of growth. After six years it attains an average height of 15.13 ± 4.6 m and a coefficient of variability of 0.3 percent. The average diameter is 19.23 ± 3.1 cm with coefficient of variability at 16 percent. Wood production/km over a six-year period is estimated at 117 m3. It attains maximum growth and wood production at Wadi bottoms where light alluvial soils and water resources are favourable.
· Albizia lebbek is found growing in municipal gardens in Aden and no correct records are available about the date of its introduction. Seeds were collected from mature stems of good morphological characteristics, propagated and planted in different localities under irrigation. It is a more vigorous grower than A. nilotica, and if watered on a deep soil, develops into a large tree. It will grow satisfactorily on a water table at 8 m, as at El-kod.
It regenerates quickly when coppiced; its leaves form good fodder for stock. It gives a very valuable timber with hard wood but is not so drought resistant as Sunt (A. nilotica), particularly in its incipient stages. It is suitable for growing around floor irrigated or well-irrigated farms; it is deciduous whereas Sunt is evergreen, and produces much denser shade than Sunt. It is a common tree in the Abyan and Lahej areas. In six years it produced 109 m3/km when planted 6 × 6 m at the Lenin State Farm under tubewell irrigation. It is planted as windbreaks, roadside and amenity plantations and known locally as "mity".
· Neem (Azadirachta indica) is a fast growing tree and more to be compared with Albizia than Sunt, though faster growing than either. Not so large as Albizia, its timber is valuable and sold at 10 Dinars/m3 at the local market. It is not so drought tolerant as Sunt. It suffers from wind mechanical effect at early stages of growth but resists at later stages. It coppices freely and regenerates prolifically from seed. It is an over green, casts a fairly dense shade, and is good for growing along water courses. The leaves are suitable for fodder but not so palatable as others; its wood is close grained and hard. In 26 months of growth it has attained an average height of 2.8 ± 0.7 m and a coefficient of variability of 25 percent, a diameter of 2.4 ± 0.9 cm and a coefficient of variability of 37.5 percent. It is a tree common in the Abyan and Lahej delta. In 1976 chlorosis of the leaf was noticed on old (15 years and above) trees, which suddenly results in drying of top branches and, later on, on total death of the trees. Were this disease to spread it would cause much damage. The incidence now is limited to individual trees and does not yet involve a large scale infestation but it causes uncertainty as to future plans for expanding plantations. The case is now under serious study at the pathology section in the El-kod Research Station.
Boswalia (Louban gum) for frankincense
Tending a nursery of Eucalyptus camaldulensis
· Damas (Conocarpus lancifolius) grows fairly rapidly if well irrigated and produces a tall-straight trunk. It is not particularly drought resistant but will grow slowly on a water table of about 8 m deep, if initially watered to the stage of establishment. It attains a good diameter/height growth if given enough planting space. At the Lenin State Farm it was planted in late 1970 at 1½-2½ m apart. There was serious competition among trees both in root and crown zones which resulted in poor growth and yield. It has attained a height of 11.7 ± 3.4 m with a coefficient of variability of 29 percent. The diameter attained was of 15.3 ± 3.5 cm and the coefficient of variability of 22.8 percent during a little less than six years. It attained a height of little more than Albizia, but the latter overcomes it in diameter growth, and thereby in volume production of wood.
Casuarina equisetifolia was introduced from South Africa through Dr. Lavranos who was doing studies on succulent plants of southwest Asia and included the People's Democratic Republic of Yemen in 1968/69. It was propagated at the El-kod Forest Nursery and planted first on a small scale. Because of its rapid growth and conical shape it was favoured among farmers for planting as windbreaks. This added to its promising adaptability, encouraged its expansion in the process of propagation and planting. It has now become one of the trees planted as windbreaks. The Casuarina is not at all drought resistant and will dry back if not regularly irrigated in areas of less than 100 mm of annual precipitation. It is a first class windbreak tree in deep alluvial soils, receiving tubewell irrigation. The best growth examples are at the Lenin State Farm in Abyan Delta. In Amgibla State Farm (mid-altitude area) Casuarina attained a height of 6.9 ± 1.6 m and a coefficient of variability of 23.3 percent in three years' time. This brings it next to Eucalyptus camaldulensis as compared to Azadirachta, Conocarpus, and Albizia spp.
Prosopis cinerea was introduced from Hadramout in 1973 and propagated in El-kod Forest Nursery. It was planted in 1974 at the El-kod Forest Research Arboretum. In the same year some saplings were planted at the Sixth Conference State Farm for demonstration purposes. It seems to be growing vigorously and with excellent performance. Based on the statistical data collected, the tree attained an average height of 5.2 ± 0.85 m and a diameter of 6.58 ± 3.7 and a coefficient of variability of 16.3 and 56.2 percent respectively, in about 26 months' time. It is drought resistant, having a spreading crown from 1½ m above ground level to the top. This makes it an excellent tree for windbreaks in areas having strong wind and shifting sands. It has a deep root system which can draw moisture from deep layers of the soils. The tree coppices freely and is excellent for fodder.
Acacia mellifera was introduced recently from Sudan and was planted in the arboretum and Sixth Conference State Farm in 1974. It was also planted for demonstration purposes. It seems to be good for hedge or anti-animal barrier if closely spaced. In early stages of growth it is vigorous and drought resistant, attaining a height of 1.5 ± 0.5 m and a crown diameter of 4.2 ± 0.9 m with a coefficient of variability of 33.3 and 37.5 percent respectively, during a 26 months' period. In the arboretum it flowers and produces seeds two years after planting. It is a good bee attractor during flowering time.
CUT DOWN FOR TIMBER Ficus vasta
Table 2. - Tabulated data showing growing stock production of exotic species in El-kod Forest Nursery from 1970-76
1 Miscellaneous are from Acacia tortilis, A. melifera, Lawsonia alba, Lantana camara, Peltophorum inerme, Kigalia pinnata, Ponganica glabra. Nerium oleander, Hibiscus spp. etc.
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