Typically this is less than 10 pounds of total

This preview shows page 5 - 8 out of 19 pages.

Typically, this is less than 10 pounds of total nitrogen per acre per year. Bacteria converts nitrogen into organic forms Fixation can occur either in free-living organisms or symbiotically in association with legumes Nitrogen is also fixed industrially through several processes. Nitrogen fixing bacteria v Nitrogen-fixing bacteria change N to a more useful form by combining it with hydrogen to make ammonia (NH 3 ) . v Other bacteria convert ammonia to nitrites and nitrates , which can be taken up by plants to make proteins. v Members of the bean family (legumes) have nitrogen-fixing bacteria living in their root tissue
Image of page 5

Subscribe to view the full document.

9/19/18 6 Ecological Implications of Human Alterations to the Nitrogen Cycle Human activities significantly impact the nitrogen cycle Burning fossil fuels, application of nitrogen-based fertilizers , and other activities have dramatically increase the amount of biologically available nitrogen in an ecosystem. Industrial nitrogen fixation has increased exponentially since the 1940s, and human activity has doubled the amount of global nitrogen fixation Nitrogen availability often limits the primary productivity of many ecosystems large changes in the availability of nitrogen can lead to severe alterations of the nitrogen cycle in both aquatic and terrestrial ecosystems. Algae blooms can be toxic to fish an other organisms
Image of page 6
9/19/18 7 Figure modified from: Lambert and Driscoll, 2003. Nitrogen Pollution: Sources to the Sea. Hanover NH. Hubbard Brook Research Foundation, 4. Fixed Nitrogen and Global Population Figure From I. Valiela. Marine Ecological Processes, Second edition. 1995. Springer-Verlag, N.Y. and J. J. Cole, B. L. Peierls, N. F. Caraco, and M. L. Pace. 1997. Nitrogen loading of rivers as a human-driven process. In M. J. McDonnell and S. T. A. Pickett, eds. Humans as components of ecosystems: the ecology of subtle human effects and populated areas. Springer-Verlag, N.Y. Nitrogen export from watersheds and human population density
Image of page 7

Subscribe to view the full document.

9/19/18 8 Figure from How a century of ammonia synthesis changed the world Jan Willem Erisman, Mark A. Sutton, James Galloway, Zbigniew Klimont & Wilfried Winiwarter. Nature Geoscience 1 , 636 - 639 (2008) Published online: 28 September 2008 doi:10.1038/ngeo325 Haber Bosch Nitrogen Nitrogen Inputs and Outputs Nitrogen cycle : A continuous series of natural processes (and artificial) by which nitrogen passes from the air to the soil, to organisms, and then returns back to the air or soil.
Image of page 8
You've reached the end of this preview.
  • Spring '14
  • DenebKarentz

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern