Nitrogen input–output budgets for lake-containing watersheds in the Adirondack region of New York

Abstract

The Adirondack region of New York is characterized by soils and surface waters that are sensitive to inputs of strong acids, receiving among the highest rates of atmospheric nitrogen (N) deposition in the United States. Atmospheric N deposition to Adirondack ecosystems may contribute to the acidification of soils through losses of exchangeable basic cations and the acidification of surface waters in part due to increased mobility of nitrate (NO 3 À ). This response is particularly evident in watersheds that exhibit 'nitrogen saturation.' To evaluate the contribution of atmospheric N deposition to the N export and the capacity of lake-containing watersheds to remove, store, or release N, annual N input-output budgets were estimated for 52 lake-containing watersheds in the Adirondack region from 1998 to 2000. Wet N deposition was used as the N input and the lake N discharge loss was used as the N output based on modeled hydrology and measured monthly solute concentrations. Annual outputs were also estimated for dissolved organic carbon (DOC). Wet N deposition increased from the northeast to the southwest across the region. Lake N drainage losses, which exhibited a wider range of values than wet N deposition, did not show any distinctive spatial pattern, although there was some evidence of a relationship between wet N deposition and the lake N drainage loss. Wet N deposition was also related to the fraction of N removed or retained within the watersheds (i.e., the fraction of net N hydrologic flux relative to wet N deposition, calculated as [(wet N deposition minus lake N drainage loss)/wet N deposition]). In addition to wet N deposition, watershed attributes also had effects on the exports of NO 3 À , ammonium (NH 4 + ), dissolved organic nitrogen (DON), and DOC, the DOC/DON export ratio, and the N flux removed or retained within the watersheds (i.e., net N hydrologic flux, calculated as [wet N deposition less lake N drainage loss]). Elevation was strongly related with the lake drainage losses of NO 3 À , NH 4 + , and DON, net NO 3 À hydrologic flux (i.e., NO 3 À deposition less NO 3 À drainage loss), and the fraction of net NO 3 À hydrologic flux, but not with the DOC drainage loss. Both DON and DOC drainage losses from the lakes increased with the proportion of watershed area occupied by wetlands, with a stronger relationship for DOC. The effects of wetlands and forest type on NO 3 À flux were evident for the estimated NO 3 À fluxes flowing from the watershed drainage area into the lakes, but were masked in the drainage losses flowing out of the lakes. The DOC/DON export ratios from the lake-containing watersheds were in general lower than those from forest floor leachates or streams in New England and were intermediate between the values of autochthonous and allochthonous dissolved organic matter (DOM) reported for various lakes. The DOC/ DON ratios for seepage lakes were lower than those for drainage lakes. In-lake processes regulating N exports may include denitrification, planktonic depletion, degradation of ...

Spatial and temporal dynamics of stream chemistry in a forested watershed

“…The largest NO − 3 fluxes from forested watersheds in the US occur with large runoff events, especially during early spring snowmelt when vegetation and microbial uptake of inorganic N is low (Mitchell et al, 1996;Baron and Campbell, 1997;Brooks and Williams, 1999;Park et al, 2003;Inamdar et al, 2004;Piatek et al, 2005). The presence of wetlands and changes in vegetative cover from coniferous to deciduous may be related to the generation and loss rates of organically-bound elements, such as DOC, DON, and Al (Campbell et al, 2002;Mitchell et al, 2003;Ito et al, 2005).…”

Nitrogen deposition and lake nitrogen concentrations: a regional analysis of terrestrial controls and aquatic linkages

“…In the terrestrial portion of the watershed reactive forms of N are taken up by terrestrial plants and microorganisms and mostly retained in soils and plant biomass (Aber et al 2003, Lovett andGoodale 2011). N exported to lakes is mainly in the form of dissolved organic nitrogen, although nitrate can also be an important component of export especially during snowmelt (McHale et al 2000, Mitchell et al 2001, Ito et al 2005. In terms of inputs to lakes, different watershed cover types (e.g., forests versus wetlands) export different quantities of N (Ito et al 2005).…”

“…N exported to lakes is mainly in the form of dissolved organic nitrogen, although nitrate can also be an important component of export especially during snowmelt (McHale et al 2000, Mitchell et al 2001, Ito et al 2005. In terms of inputs to lakes, different watershed cover types (e.g., forests versus wetlands) export different quantities of N (Ito et al 2005). Direct N deposition to the surfaces of lakes may also be an important input especially for lakes in areas of high deposition (Sullivan et al 1997).…”

“…Direct N deposition to the surfaces of lakes may also be an important input especially for lakes in areas of high deposition (Sullivan et al 1997). Hydrological losses from lakes have a strong influence on nitrogen in lakes with short water residence times (Ito et al 2005). Sedimentation and denitrification are the other losses that influence lake N, but these rates are poorly known for Adirondack lakes (Ito et al 2005).…”

“…Hydrological losses from lakes have a strong influence on nitrogen in lakes with short water residence times (Ito et al 2005). Sedimentation and denitrification are the other losses that influence lake N, but these rates are poorly known for Adirondack lakes (Ito et al 2005).…”