Chapter 8 Methods for Measuring Atmospheric Nitrogen Deposition Inputs in Arid and Montane Ecosystems of Western North America

Abstract

Abstract Measuring atmospheric deposition in arid and snow-dominated regions presents unique challenges. Throughfall, the flux of nutrients transported in solution to the forest floor, is generally the most practical method of estimating below-canopy deposition, particularly when monitoring multiple forest sites or over multiple years. However, more studies are needed to relate throughfall fluxes to total atmospheric deposition, particularly in seasonally dry regions. In seasonally snow-covered regions, the distribution of atmospheric deposition and subsequent nitrogen (N) fluxes are highly sensitive to the temporal and spatial dynamics of snow accumulation and melt. Recent developments in passive monitoring techniques for throughfall and measurement of gaseous pollutants greatly facilitate monitoring of atmospheric deposition and ambient pollutant concentrations over broader spatial scales than was previously possible. Here we focus primarily on N fluxes as N is both a limiting nutrient and a pollutant in many terrestrial ecosystems, and because sulfur (S) deposition is not a widespread problem in the West. Methods suggested for estimating spatially distributed atmospheric deposition in arid and snow-dominated systems include simulation modeling, inferential method, throughfall collection, branch rinsing, N accumulation in surface soils of arid zones, and snowpack sampling methods. Applying more than one approach is often necessary to capture the various atmospheric deposition pathways and the spatial and temporal variability of N deposition.