Evaluating Summer Rainfall through a Multilayered Largetooth Aspen Community

This paper presents results of measurements, made separately for each of four canopy layers, of throughfall and stemflow in a multilayered stand of largetooth aspen (Populus grandidentata Michx.). Each canopy layer is identified by the predominant woody or fern species. Equations describe relationships between stemflow, stem size, and storm size, and between throughfall and storm size. In general, stemflow per stem per storm increased as both stem size and storm size increased, the latter having the greater effect. The equations varied with species. General stemflow equations were constructed to calculate stemflow per stem per storm for tree sizes and storm sizes within the measured range. Throughfall per storm increased as storm size increased, but at different rates for different canopy layers. Monthly budgets of interception, stemflow, and net rainfall for the various canopies, separately and together, were computed for the summer months of 1969 using the stemflow and throughfall equations, measured gross rainfall during all summer storms, and data on canopy structure for four plots within the stand. Interception by all canopies together amounted to 22 to 46% of monthly gross rainfall. Interception from the bracken fern canopy alone was 3 to 9%. Stemflow was about 8 to 17% of the monthly gross rainfall. The highest proportion of total stemflow was from bracken fern. Net rainfall was 54 to 78% of the monthly gross rainfall.