Rotation age and fibre length of pinus patula at sao hill forest plantation, Tanzania

Abstract

This study determined the rotation age of Pinus patula grown at Sao Hill forest plantation based on growth, yield, wood properties, and economic analysis. Previous Technical Orders on rotation age were not based on these considerations. Growth, yield, wood properties, revenue, and management costs data were collected and analysed using standard procedures. The results indicate that there were fewer and lighter prunings and thinnings than specified in the respective schedules. Many trees were found to have breast height diameter below 40 cm in all compartments except one. Growth and yield results showed that for P. patula grown at Sao Hill, the equity point of Mean Annual Increment (MAI) and Current Annual Increment (CAI) were achieved at between 16 and 17 years with the maximum MAI being maintained until about 20 years. Basic density and mechanical properties showed that strong wood was obtained when trees were 16 years and above and these properties increased with age. The mean fibre length for 5 - 25 years old P. patula was found to range from 2.29 to 3.53 mm and increased with age. Fibre lengths from 11 years and above exceed the minimum (3 mm) considered suitable for pulp and paper production. Based on economic analysis, net present value (NPV) was attained at between 16 and 17 years. Based on considerations of growth and yield, wood properties and economics of rotation age; P. patula from Sao Hill is recommended to be harvested at 18 years for timber and 11 years for pulp and paper production.