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

Abstract

Interception loss was measured indirectly for 3 years in adjacent unthinned 25-year-old stands of Sitka spruce and lodgepole pine and for 2 years in a 63-year-old selectively thinned stand of Sitka spruce. For each stand measurements were made of gross precipitation, throughfall and stemflow. Interception loss was derived by subtracting the sum of throughfall and stemflow (net precipitation) 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 while those in the lodgepole pine were 33, 29 and 26 per cent. For 1979–80 and 1980–81 interception losses in the mature Sitka spruce were 44 and 53 per cent of gross precipitation. The average interception loss was 29 per cent for both pole-stage crops and 49 per cent for mature Sitka spruce. The proportions of net precipitation reaching the ground as stemflow and throughfall were 0.18 and 0.82 respectively for the pole-stage Sitka spruce, 0.14 and 0.86 for the pole-stage lodepole pine and 0.02 and 0.98 for the mature Sitka spruce.