State factor relationships of dissolved organic carbon and nitrogen losses from unpolluted temperate forest watersheds

Journal of Geophysical Research G: Biogeosciences
By:  and 

Links

Abstract

We sampled 100 unpolluted, old-growth forested watersheds, divided among 13 separate study areas over 5 years in temperate southern Chile and Argentina, to evaluate relationships among dominant soil-forming state factors and dissolved carbon and nitrogen concentrations in watershed streams. These watersheds provide a unique opportunity to examine broad-scale controls over carbon (C) and nitrogen (N) biogeochemistry in the absence of significant human disturbance from chronic N deposition and land use change. Variations in the ratio dissolved organic carbon (DOC) to nitrogen (DON) in watershed streams differed by underlying soil parent material, with average C:N = 29 for watersheds underlain by volcanic ash and basalt versus C:N = 73 for sedimentary and metamorphic parent materials, consistent with stronger adsorption of low C:N hydrophobic materials by amorphous clays commonly associated with volcanic ash and basalt weathering. Mean annual precipitation was related positively to variations in both DOC (range: 0.2-9.7 mg C/L) and DON (range: 0.008-0.135 mg N/L) across study areas, suggesting that variations in water volume and concentration may act synergistically to influence C and N losses across dry to wet gradients in these forest ecosystems. Dominance of vegetation by broadleaf versus coniferous trees had negligible effects on organic C and N concentrations in comparison to abiotic factors. We conclude that precipitation volume and soil parent material are important controls over chemical losses of dissolved organic C and N from unpolluted temperate forest watersheds. Our results raise the possibility that biotic imprints on watershed C and N losses may be less pronounced in naturally N-poor forests than in areas impacted by land use change and chronic N deposition. Copyright 2007 by the American Geophysical Union.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title State factor relationships of dissolved organic carbon and nitrogen losses from unpolluted temperate forest watersheds
Series title Journal of Geophysical Research G: Biogeosciences
DOI 10.1029/2006JG000276
Volume 112
Issue 2
Year Published 2007
Language English
Contributing office(s) Forest and Rangeland Ecosystem Science Center
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Journal of Geophysical Research G: Biogeosciences