Date of Graduation


Document Type


Degree Type



Davis College of Agriculture, Natural Resources and Design


Division of Forestry and Natural Resources

Committee Chair

Charlene Kelly

Committee Member

Mary Beth Adams

Committee Member

Louis McDonald

Committee Member

William Peterjohn


This research explored effects of ecosystem change from increased atmospheric nitrogen (N) deposition and stand conversion from mixed-species hardwood to Norway spruce in three experimental watersheds at the Fernow Experimental Forest (FEF). I measured soil aggregation and organic matter (OM) content to investigate the influence of forest fertilization in Watershed 3 (WS3), a hardwood forest receiving (NH4)2SO4 fertilizer, versus Watershed 7 (WS7), a natural hardwood forest. I compared WS7 to Watershed 6 (WS6), a converted Norway spruce (Picea abies) monoculture. I quantified WS6 and WS7 C and N ecosystem pools, including vegetation biomass, forest floor, and mineral soil, and nitrate (NO3-N) atmospheric deposition and stream export, to create a C and N ecosystem budget. WS3 and WS6 soils demonstrated macro-aggregate dispersion and greater weight in the µm aggregate size class – associated with lower soil pH – relative to the reference watershed. WS7 soils have greater aggregate weight – and in the B-horizon, greater organic matter (OM) content – in size classes 250 - 2000 µm. WS3 soils exhibit greater intra-aggregate OM beneath arbuscular mycorrhizal-associated trees with labile litter; WS7 soils contain more intra-aggregate OM beneath ectomycorrhizal-associated trees. WS6 conversion significantly impacted N cycling; atmospheric NO3-N inputs are equal, yet streamflow exports from WS6 are negligible and inorganic N content is more than 5 times lower than WS7. WS6 A-horizon microbially-active C is significantly lower. As much of the world has been exposed to similar impacts, further study to determine how these systems will respond to our changing global climate is necessary.