You are here:
ROLE OF RED ALDER IN NITROGEN LOSSES FROM FORESTED WATERSHEDS IN THE OREGON COAST RANGE
Citation:
Compton, J E., M R. Church, AND S T. Larned. ROLE OF RED ALDER IN NITROGEN LOSSES FROM FORESTED WATERSHEDS IN THE OREGON COAST RANGE. Presented at 2001 American Geophysical Union meetings, San Francisco, CA, December 10-14, 2001.
Description:
Variations in plant community composition across the landscape may have strong impacts on nutrient losses from small forested watersheds. One extreme example of this impact is the role of the nitrogen-fixing tree, red alder, in the biogeochemistry of forested watersheds in the Pacific Northwestern US. To understand the connections between landscape factors and biogeochemical fluxes, we examined over 45 small watersheds in coastal Oregon's Salmon River basin. This basin has very low atmospheric N deposition, but high soil N content and widespread distribution of red alder. Stream nitrate concentrations ranged from nearly zero to over 3 ppm nitrate-N, and were positively related to proximity to the coast and proportion of the watershed in broadleaf cover (dominated by red alder). For watersheds with less than 10% alder cover, we found a correlation between nitrate and chloride in streamwater, suggesting that chloride deposited in salt spray may displace nitrate and promote leaching. Nitrate dominated hydrologic N losses from these watersheds; dissolved organic N generally comprised less than 20% of total N in streamwater. Dissolved organic nitrogen concentrations were much less spatially variable than nitrate, but were also positively correlated with broadleaf cover. Our work indicates that these forested coastal watersheds are subject to high N losses, possibly driven by atmospheric deposition of sea salt and maintained by the shifting presence of N-fixing red alder.