Nutrient transport in surface runoff and interflow from an aspen-birch forest

Nutrients transported in surface runoff and interflow from an undisturbed aspen-birch (Populus tremuloides Michx., and Betula papyrifera Marsh.) forest (6.48 ha) in northern Minnesota were measured for 3 years. Surface runoff from snowmelt accounted for 97% of the average annual surface runoff and for 57% of the average annual water loss. Slope aspect influenced the amount, rate, and time of snowmelt runoff. In surface runoff, organic nitrogen (N) comprised 80% of the total N load, and organic (+ hydrolyzable) phosphorus (PI comprised 45% of the total P load. The quantities of cations in surface runoff were in the order of calcium (Ca) > potassium (K) > magnesium (Mg) > sodium (Na). More than 96% of all the nutrients in surface runoff were transported by snowmelt. The annual volumes of interflow varied only slightly during the 3 years. Compared with surface runoff, the amounts of all the nutrients (except Na) and their weighted concentrations decreased in interflow. These nutrient losses from the ecosystem can accumulate in surface waters.