PARTITIONING OF RAINFALL BY 3 CENTRAL HIMALAYAN FORESTS

Throughfall, interception losses and surface run-off studies during the monsoon season (June through September) in three different forests of Central Himalaya are described. The tree canopy covers of the stands were 80.0-91.5%. Canopy throughfall (throughfall directly beneath the canopy) made up 76.5% and canopy interception loss was 23.5% of the total rainfall (1965.8 mm) during the 1985 and 1986 monsoons. Values of throughfall and interception losses computed for entire forested stands (stand throughfall and stand interception) accounted for 79.6% and 20.2% of the total rainfall. The minimum canopy throughfall (74.9%) was recorded in chir pine and maximum (78.6%) in mixed banj oak-tilonj oak forest. Stand throughfall was maximum (80.7%) in mixed banj oak-chir pine forest and minimum (77.5%) in chir pine forest. Stand interception was higher in chir pine compared with mixed banj oak-chir pine and banj oak-tilonj oak forests. The highest value of surface run-off was recorded in chir pine forest which had the lowest litter interception (8.3%). Canopy throughfall and surface run-off were positively related (P < 0.01) to bulk precipitation. The low proportion of surface run-off (0.46-0.53%) is a characteristic and a special feature of the forest ecosystems of the Central Himalaya.