Effects of Fertilization of a Black Spruce Stand on Nitrogen Contents of Stemflow, Throughfall, and Litterfall

The nitrogen (N) contents of stemflow, throughfall, litter, and rain were investigated in a black spruce stand with 95% crown closure treated with three levels each of nitrogen and phosphorus fertilizers in a factorial design. Throughfall and rain were collected in standard rain gauges. Stemflow was collected using lead collars coated with an inert plastic and fixed on the tree trunks. Litter samples were collected with fiberglass screens. In all samples, NH4+-N and total-N were determined.During this study, 18–20% of the rainfall was lost through interception and evaporation, 80% was throughfall, and less than 0.5% reached the ground as stemflow. Average concentrations of NH4+-N for all fertilized plots in stemflow, throughfall, and rain were 0.15, 0.23, and 0.09 p.p.m. N, respectively, and the total-N in these samples was 1.69, 0.63, and 0.37 p.p.m. N in the same sequence. Quantities of nitrogen in the throughfall were highest in the fertilized plots, i.e. fertilization increased the concentration of NH4+-N and total-N in throughfall but not in stemflow. In both stemflow and throughfall, highest concentrations of nitrogen were recorded in June. The estimated nitrogen returned to the ground by litterfall, throughfall, stemflow, and unintercepted rain was 16.00, 4.33, 0.04, and 2.62 kg N/ha/year.