Effects of Vegetation Structure and Canopy Exposure on Small-scale Variation in Atmospheric Deposition Inputs to a Mixed Conifer Forest in California
Description: Data on rates of atmospheric deposition is limited in many montane ecosystems, where high spatial variability in meteorological, topographic, and vegetation factors contributes to elevated atmospheric inputs and to the creation of deposition hotspots. Addressing the ecological consequences of increasing deposition in these areas will require a better understanding of surface controls influencing atmospheric deposition rates at both large and small-scales. The overarching objective of this thesis research was to understand the influence of vegetation structure and canopy exposure on small-scale patterns of atmospheric sulfate, nitrate, and chloride deposition inputs to a conifer forest in the Santa Cruz Mountains, California. Throughfall ion fluxes (i.e., ions delivered in water that pass from the forest canopy to the forest floor), bulk deposition (i.e., primarily wet deposition), and rainfall data were collected during the rainy period from October 2012 to May 2013. Throughfall SO42-, Cl-, and NO3- fluxes were measured beneath eight clusters of Douglas fir (Pseudotsuga menziesii) trees (three trees per cluster) differing in tree size (i.e., diameter at breast height; DBH) and canopy exposure. In each cluster, a throughfall collector was placed 1-meter from the bole of an individual tree, for a total of 24 individual collectors. The position of each throughfall collector was recorded with a Trimble® GPS. In addition, tree height, tree diameter, and leaf area index, were measured for all trees. LiDAR data were obtained from GeoEarthScope’s Northern California Airborne LiDAR project and used to model the elevation (DEM), canopy surface height (DSM), tree height (CHM), slope, and curvature of the canopy surface across the entire study area. Over the rainy season, total throughfall flux of SO42--S, a conservative tracer of total deposition (wet + dry + fog), to Douglas fir clusters ranged from 1.44 - 3.84 kg S ha-1 wet season-1, while dry and fog deposition ranged ...
Date: May 2014
Creator: Griffith, Kereen