RAINFALL PARTITIONING IN A YOUNG HOPEA ODORATA PLANTATION

A study on rainfall interception was conducted in a young Hopea odorata plantation at Bukit Tarek Experimental Watershed near Kerling, Selangor. Two interception plots were established, each consisting of 36 trees. Gross rainfall (Pg), stemflow (Sf) and throughfall (Tf) were measured to determine the interception loss. The observation period was between October 2006 and December 2007. Based on 65 successfully measured storm events, the average Tf was 83.2% of Pg in plot 1 and 77.4% in plot 2. Average Sf was 4.1% in plot 1 and 3.1% in plot 2. Interception losses were 12.7 and 19.5% for plots 1 and 2 respectively. The canopy storage S differed greatly between plots: 1.42 mm in plot 1 and 1.49 mm in plot 2, while the trunk storage capacity St was -0.171 mm in plot 1 and 0.127 mm in plot 2. The negative value of St indicated that Sf occurred immediately after rain water flowed down the tree trunk. The St amount was either so small or the tree trunk did not hold significant amount of water. Other parameters measured were tree height, stem diameter, crown area and crown depth. The correlation analysis showed that all tree parameters in both plots did not have relationship with Tf. Similar result was also obtained for Sf in plot 1. However, there were correlations between Sf and all tree parameters in plot 2. In multiple regression analysis, there were no key tree characteristics influencing the partitioning of rainfall except for crown depth that significantly influenced Sf in plot 1. The trees of H. odorata were still small that it could not significantly influence the rainfall interception. Hence, rainfall-intercepted processes for young H. odorata trees were only dependent on rainfall characteristics.