ECOLOGICAL REQUIREMENTS

Soil Requirements

Teak can grow in a variety of soils. The quality of its growth, however, depends on the depth, structure, porosity, drainage and moisture-holding capacity of the soil. It develops best on deep, well-drained and fertile soils, especially on volcanic substrata such as igneous and metamorphic soils or on alluvial soils of various origins. The optimal soil pH is between 6.5 and 7.5. The calcium content of the soil is also an important factor; calcium deficiency in the soil results in stunted growth of teak (Kaosa-ard, 1981).

Studies at FRIM indicate that good management techniques may be able to improve the performance of teak on problem soils.

Growth Performance on Some Soils in Peninsular Malaysia

Unmanaged Stands of Teak

Soil types were found to have a significant influence on teak growth if left unmanaged (Table 3). Better growth was observed on the Penambang series (riverine soils) and the Serdang series (sandstone-derived soils) than on the shallow and moderately deep stony shale soils of the Kuah and Batu Lapan series, respectively. Growth of teak crops on the laterite soils of the Gajah Mati and Pokok Sena series was drastically (30 percent) lower than on the Penambang and Serdang series.

These results seem to indicate that teak cannot do well on laterite, compacted and shallow subsoils if unattended after planting. However, rubber plantations have succeeded on such soils when management has included adequate soil preparation such as ploughing and good silvicultural practices. This suggests that if intensive management practices and good fertilization programs are followed, it is probable that teak could do well in such soil types. Experiments have now been initiated on growth and management of teak on poor soils.

New Plantings Under Plantation Management Regimes

Early growth results in trials to evaluate optimally managed teak on various soil types and under various ecological conditions support the suggestion that teak can perform well on problem soils if properly managed. To reduce costs and to ensure that optimal silvicultural practices would be followed, these trials have been carried out on small-scale farmers' plots under an arrangement termed "smart partnership": farmers benefit from free advice, good-quality seedlings, agricultural inputs from FRIM and the returns from the final crop harvest, while FRIM in turn benefits from the small holder's labor for the management of the plot and access to the growth data.

The growth results of the young plantings on some of the problematic soils appear to be good. Monitoring of these plots will be continued until the crop is harvested.

Temperature and Rainfall

Teak grows best when the minimum monthly temperature is above 13oC and the maximum monthly temperature is below 40oC. Optimal rainfall for teak ranges between 1,250 and 3,750 mm per year; however, for the production of good-quality timber the species requires a dry season of at least four months with less than 60 mm precipitation (Kaosa-ard, 1981).

In Malaysia, various small plot studies in Perak (rainfall 2,800 mm), Selangor (rainfall 2,500 mm), Kepong (rainfall 2,600 mm) and Johore (rainfall 2,700 mm) over the past three to five years have shown that teak can thrive equally well, if not better, in regions that are wetter and hotter than those where it has usually been grown. The early growth performance of the trees in these wetter, hotter regions has been remarkable and has sparked interest in promoting teak on a large scale in Malaysia.

A report from India (Kondas, 1995) shows that teak responds very well in terms of growth and girth increment in areas where the trees receive at least sufficient moisture for most of the year when compared with growth in monsoon areas.

There is a misconception that annual growth rings, which impart grain structure to the logs, occur only in teak trees growing in zones that have distinct rainy and dry seasons and not in those growing in regions where rainfall is received year round. It is probable that trees grown in zones with a long dry period will have very distinct, closely packed concentric rings owing to the inactivity of the cambium during the long dry spell. However, the growth ring continues to be formed in all climatic conditions, even where there is year-round high rainfall.