Skip to page content
USDA Forest Service
  
Treesearch

Research & Development Treesearch

 
Treesearch Home
About Treesearch
Contact Us
Research & Development
Forest Products Lab
International Institute of Tropical Forestry
Northern
Pacific Northwest
Pacific Southwest
Rocky Mountain
Southern
Help
 

GeoTreesearch


Science.gov - We Participate


USA.gov  Government Made Easy


Global Forest Information Service

US Forest Service
P.O. Box 96090
Washington, D.C.
20090-6090

(202) 205-8333

You are here: Home / Search / Publication Information
Bookmark and Share

Publication Information

(664 KB bytes)

Title: Nitrogen Excess in North American Ecosystems: Predisposing Factors, Ecosystem Responses, and Management Strategies

Author: Fenn, Mark E.; Poth, Mark A.; Aber, John D.; Baron, Jill S.; Bormann, Bernard T.; Johnson, Dale W.; Lemly, A. Dennis; McNulty, Steven G.; Ryan, Douglas F.; Stottlemyer, Robert

Date: 1998

Source: Ecological Applications. 8(3). 1998. pp. 706-733

Publication Series: Not categorized

Description: Most forests in North America remain nitrogen limited, although recent studies have identified forested areas that exhibit symptoms of N excess, analogous to overfertilization of arable land. Nitrogen excess in watersheds is detrimental because of disruptions in plant/soil nutrient relations, increased soil acidification and aluminum mobility, increased emissions of nitrogenous greenhouse gases from soil, reduced methane consumption in soil, decreased water quality, toxic effects on fresh-water biota, and eutrophication of coastal marine waters. Elevated nitrate (NOT) loss to groundwater or surface waters is the primary symptom of N excess. Additional symptoms include increasing Nconcentrations and higher N:nutrient ratios in foliage (i.e., N:Mg, N:P), foliar accumulation of amino acids or NO.:, and low soil C:N ratios. Recent nitrogen-fertilization studies in New England and Europe provide preliminary evidence that some forests receiving chronic N inputs may decline in productivity and experience greater mortality. Long-term fertilization at Mount Ascutney, Vermont, suggests that declining and slow N-cycling coniferous stands may be replaced by fast-growing and fast N-cycling deciduous forests. Symptoms of N saturation are particularly severe in high-elevation, nonaggrading spruce-fir eco-systems in the Appalachian Mountains and in eastern hardwood watersheds at the Fernow Experimental Forest near Parsons, West Virginia. In the Los Angeles Air Basin, mixed conifer forests and chaparral watersheds with high smog exposure are N saturated and exhibit the highest streamwater NO; con-centrations for wildlands in North America. High-elevation alpine watersheds in the Colorado Front Range and a deciduous forest in Ontario, Canada, are N saturated, although N deposition is moderate (-8 kg.ha-?.yr-?). In contrast, the Harvard Forest hardwood stand in Massachusetts has absorbed >900 kg N/ha during 8 yr of N amendment studies without significant NOi leaching, illustrating that eco-systems vary widely in the capacity to retain N inputs. Overly mature forests with high N deposition, high soil N stores, and low soil C:N ratios are prone to N saturation and NO7 leaching. Additional characteristics favoring low N retention capacity include a short growing season (reduced plant N demand) and reduced contact time between drainage water and soil (i.e., porous coarse-textured soils, exposed bedrock or talus). Temporal patterns of hydrologic fluxes interact with biotic uptake and internal cycling patterns in determining ecosystem N retention. Soils are the largest storage pool for N inputs, although vegetation uptake is also important. Recent studies indicate that nitrification may be widespread in undisturbed ecosystems, and that microbial assimilation of NO.7 may be a significant N retention mechanism, contrary to previous assumptions. Further studies are needed to elucidate the sites, forms, and mechanisms of N retention and incorporation into soil organic matter, and to test potential management options for mitigating N losses from forests. Implementation of intensive management practices in N-saturated ecosystems may only be feasible in high-priority areas and on a limited scale. Reduction of N emissions would be a preferable solution, although major reductions in the near future are unlikely in many areas due to economic, energy-use, policy, and demographic considerations.

Keywords: atmospheric nitrogen deposition: eutrophication, forest ecosystems, nitrate leaching, nitrogen cycling, nitrogen saturation: soil acidification.

Publication Notes:

  • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
  • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.

XML: View XML

Citation:


Fenn, Mark E.; Poth, Mark A.; Aber, John D.; Baron, Jill S.; Bormann, Bernard T.; Johnson, Dale W.; Lemly, A. Dennis; McNulty, Steven G.; Ryan, Douglas F.; Stottlemyer, Robert 1998. Nitrogen Excess in North American Ecosystems: Predisposing Factors, Ecosystem Responses, and Management Strategies. Ecological Applications. 8(3). 1998. pp. 706-733

 


 [ Get Acrobat ]  Get the latest version of the Adobe Acrobat reader or Acrobat Reader for Windows with Search and Accessibility

USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.