Effect of Two Years of Nitrogen Deposition on Shoot Growth and Phenology of Engelmann Spruce (Picea engelmannii Parry ex Engelm.) Seedlings

Abstract

As a result of anthropogenic combustion processes, ecosystems in the eastern and western United States and Europe have experienced elevated atmospheric deposition of nitrogen for most of this century and have begun to show symptoms of decline. If there is a cause and effect relationship between nitrogen deposition and ecosystem decline, one would expect that the current symptoms are a result of the cumulative effect of years of deposition. Deposition of anthropogenically produced nitrogenous compounds has increased along the Colorado Front Range in the past decades as a result of increased urbanization (Sievering et al., 1992, 1996; Williams et al., 1996). Annual pollutant deposition rates increase with elevation (Gilliam et al., 1996) due to the greater amount of precipitation at high elevations. Therefore, the health of high elevation Engelmann spruce (Picea engelmannii Parry ex Engelm.) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) forests may be at risk from sustained nitrogen inputs.