Consequences of nitrate leaching following stem-only harvesting of Swedish forests are dependent on spatial scale

Abstract

Short-term increases in soil solution nitrate (NO 3 −) concentration are often observed after forest harvest, even in N-limited systems. We model NO 3 − leaching below the rooting zone as a function of site productivity. Using national forest inventories and published estimates of N attenuation in rivers and the riparian zone, we estimate effects of stem-only harvesting on NO 3 − leaching to groundwater, surface waters and the marine environment. Stem-only harvesting is a minor contributor to NO 3 − pollution of Swedish waters. Effects in surface waters are rapidly diluted downstream, but can be locally important for shallow well-waters as well as for the total amount of N reaching the sea. Harvesting adds approximately 8 Gg NO 3–N to soil waters in Sweden, with local concentrations up to 7 mg NO 3–N l −1. Of that, ∼3.3 Gg reaches the marine environment. This is ∼3% of the overall Swedish N load to the Baltic.