Productivity and Volume Estimates
The productivity of teak plantations has been studied across a broad range of countries through permanent sample plots. The earliest yield table for teak was constructed by von Wulfing (1932) for plantations on Java, Indonesia. Laurie and Ram (1939) constructed a yield table for teak plantations distributed over present-day India, Myanmar and Bangladesh. More recently, yield tables have been developed using data from permanent and temporary sample plots for plantations of teak established outside its natural range, including provisional yield tables for Trinidad and Tobago (Miller, 1969), Côte d'Ivoire (Maitre, 1983), Nigeria (Abayomi, 1984) and Sri Lanka (Phillips, 1995).
An important feature of all teak yield tables is the early peak of mean annual volume increment (MAI), generally between six and 20 years. Because teak is planted and managed for timber production, size plays a decisive role in determining harvesting, rather than the age of maximum volume production. The rotation age of plantation teak in its natural range has varied between 50 and 90 years, while outside its range the rotation age is between 25 and 60 years. Table 2 compares the MAI at 50 years (taken as the average age at harvest) and at the age of maximum volume production, as derived from the various yield tables.
There is a paucity of data on actual yield obtained at harvest of teak from different site classes and countries. There is limited data available from Indonesia and India. In Indonesia, the average actual MAI at harvest age, with rotation varying between 40 and 90 years, was 2.91 m3 per hectare per year (FAO, 1986), while Table 2 estimates an average of 13.8 m3 per hectare per year. Perum Perhutani, the State-owned company that manages the major teak plantation areas in Indonesia, has confirmed that the actual yield of teak at final felling is about 100 m3 per hectare at about 70 years, with a similar volume obtained from thinnings. The MAI at rotation age is, consequently, about 3 m3 per hectare per year (Perum Perhutani, unpublished data).
Similarly, in India, the actual yield obtained from thinnings and final fellings in Koni Forest in Kerala State averaged 172 m3 per hectare with a 70-year rotation, giving an MAI of about 2.5 m3 per hectare per year (FAO, 1985). The site class for teak in Koni Forest was considered to be between the average and the best, but poor stocking was considered the main reason for such a low yield. Similar yields were also found during plantation inventory of teak in Bangladesh. However, in teak plantation inventories in Benin and Ivory Coast, the estimated MAI with a 40- to 50-year rotation age was found to range between 8 and 11 m3 per hectare per year. The estimated yield in Costa Rica with 40-year rotation is 6.9 m3 per hectare per year (M. Gomez, personal communication).
TABLE 2. MAI maximum and at 50 years rotation age for different site classes (m3/ha/year)
|Trinidad and Tobago*
Yield tables have been prepared based on an inadequate number of sample plots and are provisional.*
The general conclusion is that the actual productivity of teak plantations has often been much lower than indicated in yield tables; this is probably because sample plots are likely to receive more management attention than field plantings and because of statistical inadequacies of the samples.
Pandey (1996) has developed a model to predict the potential productivity of teak plantations at the global or regional level using climatic factors. Climatic variables explain 59 percent of the variance of the potential yield of teak plantations. Relative humidity and annual rainfall were identified as the most important climatic factors influencing the growth of teak. Above certain upper limits, however (70 percent and 2,000 mm per year, respectively), increases in their values result in successively less increase in the potential yield. Teak is a fine example of the coppice species.