Teak Yield Regulation in the Natural Forests of the Tharrawaddy Forest Division, Myanmar : 138 Years of the Girth Limit Selection System

Abstract

Attempts to introduce scientific management techniques to forestry in Myanmar began in 1856 with the appointment of D. Brandis, a German botanist, to manage the Pegu hill forests of the then Burma. One of Brandis's main management objectives was to ensure a permanent and sustained yield of teak (Tectona grandis) logs from the area's natural forests. To this end a girth limit selection system was adopted in the Tharrawaddy forests of Pegu, with the minimum exploitable girth limit set at 6 feet. Since then the actual yield has fluctuated widely between 1588 and 9250 trees per year, because of changes in the estimates of forest growth rates. Until 1927, the actual rate of harvesting by girdling was based on estimates of annual yield. The girdling is done with a broad circular cut through the bark to the sapwood, and the tree is the left standing for 3 yr to dry evenly so that it produces a good-quality timber and can be floated down river after felling; trees under exploitable girth are also girdled if they are unlikely to survive the next felling cycle. Unstable social and political conditions prevented regular girdling and silvicultural treatment between 1928 and the early 1960s, but as social conditions improved from the 1960s, girdling was conducted in some years. The analysis of the status of the Tharrawaddy forest division's teak stocks given in this paper uses data from 1912-13, 1982-86 and 1994. It shows that there was poor teak regeneration in low girth classes but an increase in the number of trees in higher girth-classes between 1912 and 1982, and a drastic drop in the growing stock of all girth classes between 1982 and 1994. The poor regeneration was caused by a lack of adequate silvicultural operations during the 40 to 50 years prior to the 1980s, while illegal logging is the primary cause of the decline in growing stock. Strong action needs to be taken to expand the area of new plantings, to prevent excessive logging, and to increase public participation in forest management. Clear and firm policies to achieve these objectives should become fundamental components of all of Myanmar's future forest management plans.