Growth and yield
The considerable amount of information published on the growth of A. mangium confirms that the species can achieve the mean annual increment (MAI) in DBH of up to 5 cm and MAI in height of up to 5 m in the first four or five years. However, growth declines rapidly after seven or eight years, except under very ideal conditions or over long ( 20 years) periods, the tree will probably not grow beyond 35 cm in DBH and 35 m in height (Tsai 1993).
In the studies on this species in Indonesia, growth rate varies considerably with site, age and spacing (Krisnawati et al. 2011). Comparisons can be made on the basis of the mean annual increment (MAI) values. The MAI for diameter ranges from 1.4 to 7.3 cm/year. High DBH MAI values (more than 4 cm/year) are recorded for stands less than 3 years old and after this age the diameter MAI values generally decline towards 1.5-2 cm/year. The MAI for height ranges from 1.8 to 5.8 m/year, and high values of height MAI (more than 4 m/year) have been recorded for stands less than 3 years old, although a height MAI of more than 4 m/year has also been reported in older stands in several sites in Riau and in South Sumatra. As with diameter MAI, height MAI drops, declining towards 2-2.5 m/year. Growth generally declines rapidly after 8 years.
Choice of the correct provenance for a particular planting site can have a major influence on growth rate and yield. On an Imperata grassland site in South Kalimantan and Indonesia, Tuomela et al. (1996) reported there was up to a threefold differences in volume production between the best growing provenances (60-90 m3/ha) and the poorest performers (30-50 m3/ha) at 26 months. In the same study, growth after singling and pruning at 8 months was found to be only about 70% of that of untreated plots. These treatments were deemed by the authors as being undesirable if growth rate is the first priority. In another trial in the same region, Otsamo et al. (1996) reported the MAI for A. mangium at 41 months was up to 39 m3/ha. At Kampar Kiri-Riau, Indonesia, the best provenance in a trial was reported as giving an MAI of 41.4 m3/ha at 2.5 years (Leksono et al. 1996).
In a study conducted in Kerala state in India (Buvane-swaran 2005), the MAI in terms of GBH was worked out for three agro-climatic zones in Kerala and the comparison of the results showed that high altitude zone registered greater MAI in girth (9.6 cm/year) than in southern (8.0 cm/year) and northern zone (9.4 cm/year). Generally, it is observed that within a plantation and within a zone variation in GBH of A. mangium GBH was greater than that of zones in Kerala. However, in humid regions, the productivity ranged from 35 to 45 m3/ha/year particularly in the southern zone of Kerala. On the other hand, in sub-humid climatic condition with red loamy soils as observed in some belt of northern zone, the productivity ranged from 20 to 25 m3/ha/year. A. mangium was observed to be a species for wet zones and hence, localities with long dry spell were not being appropriate for establishing A. mangium plantation. Heart rot / root rot diseases were being risk factors involved in cultivation of Mangium in these dry regions.
Pest and Diseases
Important insect-pests
Hutacharern (1993) has described 30 insect species attacking A. mangium, together with other 48 insect species reported on A. mangium. Among theses, only a few species have profound effects. Important insect pests are root feeders (Stenocera aequisignata and termite), branch and stem borers (Synoxylon spp.), and the red coffee borer (Zeuzera coffeae). These can cause death, deformity, or reduced biomass production of A. mangium, and thus are the insects that must be carefully monitored and for which preventive measures should be employed (Hutacharern 1993).
For preventive control measures of Stenocera in the nursery isobenzan (Telodrin) application at 1.3 gallon per ha to the soils or beds or, where polythene sleeves are used, mixing the filling soil with one part isobenzan in 500 parts water before or after filling is recommended (Sharma et al. 1966). Further application ofthe chemical around the collar of each plant for two consecutive years after planting in March is required in areas with dense Sternocera populations. For controlling red coffee borer insecticides can be injected into the holes where larva pushes out their frass. To save the trees, this direct injection must be done at the earliest detection of insects (Hutacharern 1993). The adults of branch and stem borers (Synoxylon spp.) attack shoots and young stems and kill or render them to breakage. To control these insects, removing and burning broken branches in which breeding has taken place is recommended.
Important diseases
Detailed accounts of diseases of A. mangium have been given by See (1993). The common diseases of A. mangium seedlings in nursery are damping off, powdery mildew, stem galls, die-back, leaf spots, charcoal root rot disease and root knot. All these are mostly common diseases of many tree species and can be controlled by conventional nursery management techniques and prophylactic fungicidal sprays (See 1993).
Important tree diseases in plantations are root rots, heart rot, pink disease, die-back and stem canker. Root rots are caused by many fungal species like-Ganoderma spp., Phellenus spp. and Rigidoporus lignosus. Initial root rot symptoms resemble those of nutrient deficiencies. In more advanced stages when major portions of roots decayed, fallen trees or standing dead trees are good indicators of root rots (See 1993). There are no specific control measures for these diseases. Only dead and diseased trees can be destroyed to avoid spread of the disease.
The heart rot is only evident upon felling of trees because diseased trees outwardly appear healthy and vigorous. The dieback is caused probably because of combination of several factors like prolonged drought period and fungal infections. Cankers associated with decayed branch stubs and pruning wounds are good indicators of heart rot. Infected trees can continue to grow vigorously to maturity. Management options include adopting silvicultural practices that limit wounds to the stem, including early singling of multistemmed trees, short rotations and selecting provenances for slender branches and single stems. At present there are no practical measures for this disease.
Wood Properties and Utilization
Anatomical, physical and mechanical properties of A. mangium wood
The sapwood of A. mangium is white and sharply defined from the darker brown heartwood. The wood has fine texture and straight or interlocked grain. The average values for fiber length, diameter, lumen diameter and wall thickness are 934, 25, 18 and 3.3 μm for 4-year-old samples and 1017, 20, 12 and 4.3 μm for 8-year-old samples respectively. The fibre length increases from pith to bark and decreases with stem height. The vessel percentage decreases with increasing tree height. The wood is diffuse-porous with mostly solitary vessels. The rays are uniseriate. The average percentage of fibres, vessels and rays are 85, 7-11 and 5-6 respectively. The average fibre length is reported to be 1.0-1.2 mm (1,000-1,200 μm).
A. mangium has a comparatively low proportion of parenchymatous cells, a relatively high proportion of prosen-chymatous cells and a low proportion of vessels, indicating satisfactory strength properties. It is short fibred (870 μm), characterized with small fibre diameter (18.9 μm) and small wall thickness (2.7 μm). Wu et al. (1988) studied the anatomical structure of A. mangium wood. They observed libriform fibres with inclusions, small longitudinal parenchyma with calcium crystals and vessels with silica crystals. Although the mean value of specific gravity of trees in natural stands is 0.56-0.60, plantation grown lumber is found to have a low range of specific gravity (0.40-0.45) (Mergen et al. 1983). Peh and Khoo (1984) also reported a low density for A. mangium wood (380-480 kg/m3). Scharai-Rad Kambey (1989), from Indonesia, reported about the properties and possible uses of the wood of mangium, and the wood density of 501 kg/m3.