Predicting the optimal rotation length of Teak plantations using a simulation model

Abstract

The traditional problem in Forest Economics has been mainly dealt with the estimation of optimalrotation length for sustainable management. However, given the limitation of the availability of timeseries data on growth and management in forest plantations in Sri Lanka, such estimations are notfeasible. Against this background, this study attempted to develop a simulation model and predictrotational interval of teak plantation under different management conditions.

A field survey was conducted to identify the plantation related parameters in the Kurunegala District.Meantime, a simulation model was developed with Microsoft Visual Basic and Microsoft Excel usingthe equations specified in the Teak Management Plan (1997) to supplement the field data. The pastdata obtained from the Forest Department was used to parameterize the model. Using the age andthe height of a plantation at a particular time, the model was capable of predicting the plantationrelated parameters such as dbh and timber volume over the time.

According to the values predicted by the simulation model, four different categories were identifiedbased on the site index, which represents the level of growth of a stand. Rotational interval wasestimated using the Faustman rotational model at different discount rates. Thereby it was estimatedthat the rotational intervals for the four categories at discount rates 10%, 15% and 20% as 19, 17 and15 years respectively. The internal rate of return obtained through the simulation was above themarket rate of 12%. Though the model yielded shorter rotational intervals than the present fieldvalues, the approach could be used in future with more reliable field data.