Abstract

The plantations raised by the Social Forestry Wing of the Kerala Forest Department from 1985 to 1990 in Kerala under the World Bank Scheme were assessed for survival through a stratified two-stage sampling plan. Strata were formed based on year of planting and type of plantation. The first-stage units were plantations and second-stage units were small rectangular plots. About 27 per cent of the existing plantations were covered with proportional allocation of the sampling units among the strata. Survival rates found to vary with type of plantation and year of planting. Survival shifted from 80 per cent in younger years to around 60 per cent in later years. Productivity of four important species included in the planting programme was assessed through mean tree method. The species were Acacia auriculiformis, Casuarina equisetifolia, Eucalyptus grandis and Grevillea robusta. All the above species except Grevillea robusta exhibited high potential productivity. Strip and small block plantations in general fared better than large block plantations with respect to the total biomass. Moisture content on dry weight basis of different components of trees was worked our for the four important species mentioned above through mean tree method for two of the species through allometric method. The overall moisture content of trees of Acacia auriculiformis varied form 103 per cent at 3.5 years to 96 per cent at 6.5 years. Tree of Casuarina equisetifolia showed an overall moisture content of 94 per cent at 3.5 years which decreased to 82 per cent at 6.5 years. In the case of Eucalyptus grandis moisture content of trees decreased from 163 per cent at 5.5 years to 106 per cent at 7.5 years as observed through mean tree method. Greviallea robusta showed an overallmoisture content of 92 per cent of trees at 3.5 years and 98 per cent for trees at 4.5 years through mean tree method. Plantations have been raised over an area of 20, 408 ha till 1990-91 under the World Bank Scheme in Kerala. Major portion of this area falls under 'large block' category. As many as 70 species are found planted in these plantations more important of which are the species planted over the years. Rotation age which changes with the objects of management vary with the species. A 7-year rotattion was proposed for Acacia auriculiformis based on a previous study by the institute. The present study has indicated the need for thining for Casuarina equisetifolia at the end of 4 years in good quality sites. Harvesting age could be extended to 7th or 8th year for the same species in poor quality sites. Average site index for plantations ofAcacia auriculiformis and Casuarina equisitifolia raised under the World Bank Scheme have been worked out which along with the other parameters like roatation age and stocking level at harvest in useful for working out the annual outturn from the plantations. Provisional volue table and variable density yield table prepared for Casuarina equisitifolia are additional outputs of the present study