Interception of precipitation by pole-stage Sitka spruce and lodgepole pine and mature Sitka spruce at Kielder Forest, Northumberland

Interception loss was measured indirectly for 3 years in adjacentunthinned 25-year-old stands of Sitka spruce and lodgepole pineand for 2 years in a 63-year-old selectively thinned stand ofSitka spruce. For each stand measurements were made of grossprecipitation, throughfall and stemflow. Interception loss wasderived by subtracting the sum of throughfall and stemflow (netprecipitation) from gross precipitation. For the years 1977–78, 1978–79 and 1979–80,interception losses in the pole-stage Sitka spruce were 32,28 and 27 per cent of gross precipitation respectively whilethose in the lodgepole pine were 33, 29 and 26 per cent. For1979–80 and 1980–81 interception losses in the matureSitka spruce were 44 and 53 per cent of gross precipitation.The average interception loss was 29 per cent for both pole-stagecrops and 49 per cent for mature Sitka spruce. The proportions of net precipitation reaching the ground asstemflow and throughfall were 0.18 and 0.82 respectively forthe pole-stage Sitka spruce, 0.14 and 0.86 for the pole-stagelodepole pine and 0.02 and 0.98 for the mature Sitka spruce.