نتایج جستجو برای: watersheds

تعداد نتایج: 5005  

2012
Shuiwang Duan Sujay S. Kaushal Peter M. Groffman Lawrence E. Band Kenneth T. Belt

[1] Watershed export of phosphorus (P) from anthropogenic sources has contributed to eutrophication in freshwater and coastal ecosystems. We explore impacts of watershed urbanization on the magnitude and export flow distribution of P along an urban-rural gradient in eight watersheds monitored as part of the Baltimore Ecosystem Study Long-Term Ecological Research site. Exports of soluble reactiv...

2004
Tanja N. Williamson Robert C. Graham Peter J. Shouse

Forty years after conversion from chaparral to perennial veldt grass in the San Dimas Experimental Forest, we compared land surface and soil properties between areas of the two vegetation types. Our objective was to evaluate the impact of this vegetation conversion on the soil physical properties likely to impact zero-order watershed hydrology. In three watersheds of each vegetation type, surfa...

Journal: :Proceedings of the National Academy of Sciences of the United States of America 2013
Charles C Rhoades James H McCutchan Leigh A Cooper David Clow Thomas M Detmer Jennifer S Briggs John D Stednick Thomas T Veblen Rachel M Ertz Gene E Likens William M Lewis

A current pine beetle infestation has caused extensive mortality of lodgepole pine (Pinus contorta) in forests of Colorado and Wyoming; it is part of an unprecedented multispecies beetle outbreak extending from Mexico to Canada. In United States and European watersheds, where atmospheric deposition of inorganic N is moderate to low (<10 kg⋅ha⋅y), disturbance of forests by timber harvest or viol...

2003
JOHN L. CAMPBELL JAMES W. HORNBECK MYRON J. MITCHELL MARY BETH ADAMS MARK S. CASTRO CHARLES T. DRISCOLL JEFFREY S. KAHL JAMES N. KOCHENDERFER GENE E. LIKENS JAMES A. LYNCH PETER S. MURDOCH SARAH J. NELSON JAMES B. SHANLEY

Input-output budgets for dissolved inorganic nitrogen (DIN) are summarized for 24 small watersheds at 15 locations in the northeastern United States. The study watersheds are completely forested, free of recent physical disturbances, and span a geographical region bounded by West Virginia on the south and west, and Maine on the north and east. Total N budgets are not presented; however, fluxes ...

2012
H. Ssegane E. W. Tollner Y. M. Mohamoud T. C. Rasmussen J. F. Dowd

0022-1694/$ see front matter 2012 Elsevier B.V. A doi:10.1016/j.jhydrol.2012.01.035 ⇑ Corresponding author. Tel.: +1 706 202 8193. E-mail addresses: [email protected] (H. Ssegane), Tollner), [email protected] (Y.M. Mo (T.C. Rasmussen), [email protected] (J.F. Dowd). Hydrological flow predictions in ungauged and sparsely gauged watersheds use regionalization or classification of hydrologi...

2010
J. M. Hathaway W. F. Hunt

Studies have shown stormwater runoff is a contributor to elevated indicator bacteria concentrations in surface waters. These elevated concentrations may indicate a heightened human health risk and lead to water quality violations as concentrations exceed regulatory standards. Total Maximum Daily Loads (TMDLs) are commonly established for indicator bacteria, requiring modeling and watershed plan...

Journal: :Journal of environmental quality 2012
Mark Gabriel Randy Kolka Trent Wickman Laurel Woodruff Ed Nater

The focus of this study is to investigate processes causing the observed spatial variation of total mercury (THg) in the soil O horizon of watersheds within the Superior National Forest (Minnesota) and to determine if results have implications toward understanding long-term changes in THg concentrations for resident fish. Principal component analysis was used to evaluate the spatial relationshi...

Journal: :The Science of the total environment 2005
Steven J Balogh Yabing H Nollet Heather J Offerman

Methylmercury (MeHg) bioaccumulates in aquatic food webs and can pose health risks to animals at higher trophic levels. Characterization of MeHg production in and export from watersheds can help clarify exposure scenarios for aquatic life downstream. A number of studies have demonstrated that anoxic conditions in the saturated soils of wetlands can promote the production of MeHg, and these wetl...

2008
J. L. Steiner E. J. Sadler J. - S. Chen G. Wilson D. James B. Vandenberg J. Ross T. Oster K. Cole

The USDA Agricultural Research Service has supported watershed research since the 1930s. Data from USDA Agricultural Research Service watersheds have been disseminated independently at each location, hindering multi-site analyses. A virtual team spanning diverse organizational units developed a web-based system, Sustaining the Earth’s Watersheds– Agricultural Research Data System (STEWARDS) tha...

Journal: :Journal of environmental quality 2016
Mark B David Lowell E Gentry Corey A Mitchell

Sulfur received extensive study as an input to terrestrial ecosystems from acidic deposition during the 1980s. With declining S deposition inputs across the eastern United States, there have been many studies evaluating ecosystem response, with the exception of agricultural watersheds. We used long-term (22 and 18 yr) sulfate concentration data from two rivers and recent (6 yr) data from a thir...

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