Introductions

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Introductions

• B.S. Ecology from Bates College, ME
• M.S. Ecological and Evolutionary Biology from
  Brown University, RI
• LUCE Fellowship in Dakar, Senegal with the World
  Wildlife Fund West African Marine Ecoregion
  Marine Protected Area Program
• Legislative Assistant for Congresswoman Madeleine
  Z. Bordallo (Guam)
• Chairwoman of the House Subcommittee on
  Fisheries, Wildlife and Oceans

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Controls on carbon and nitrogen accumulation and
loss in arctic tundra ecosystems
Marselle Alexander-Ozinskas August 2008
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Arctic Tundra

• Latitudes 55 to 70 North
• Accounts for 20 of earths land surface
• Low temperatures and short growing seasons
• ?Summer average temperature 12 C
• Winter average temperature -34 C
• Low biodiversity, low nutrients
• Presence of permafrost
• Low precipitation

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Climate change and carbon storage

• Most of terrestrial C stocks are in soils.
• 1/3 of the global soil carbon pool is stored in
  northern latitudes
• These higher latitudes have warmed more than
  equatorial regions in the past century
• ? The dominant effects of warming on C stocks are
  mediated by nitrogen, and corresponding changes
  to the N cycle

The World's CarbonReservoirs Size (Gt C)
    Atmosphere 750        
    Forests 610        
    Soils 2000        
    Surface ocean 1020        
    Deep ocean 38100        
    Fossil fuels  
        Coal 3000
        Oil 500
        Natural gas 500
    Total fossil fuel 4000        
Adapted from Kasting, 1998
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Nitrogen

• Changes in ecosystem N are intrinsically linked
  with changes in C due to stoichiometric
  requirements for production of organic matter
• Nitrogen is a limiting nutrient to growth in most
  terrestrial ecosystems
• Effects of warming alter the N cycle, changing
  composition, productivity, and other properties
  of many natural ecosystems

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Simplified Soil N Cycle
Atmosphere N2
N2
N2O
NOx
Biological N fixation
Lightning
Small OM uptake
Soil Organic Matter
Mineralization
NH4
NO3-
NO2
Nitrification
N2O
NOx
Aerobic
Soil Organic Matter
NH4
Mineralization
Denitrification
Anaerobic
Leaching
(Adapted from Schlesinger 1995)
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Effects of Warming
Atmosphere N2
N2
N2O
NOx
C
Biological N fixation
Lightning
Small OM uptake
Soil Organic Matter
Mineralization
NH4
NO3-
NO2
Nitrification
N2O
NOx
Aerobic
Soil Organic Matter
NH4
Mineralization
Denitrification
Anaerobic
Leaching
(Adapted from Schlesinger 1995)
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What C and N cycling processes should be more
responsive to global warming? What are the short
and long-term controls over these processes?
What are the implications for overall arctic C
balance?
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Fertilizer Addition
Atmosphere N2
N2
N2O
NOx
Biological N fixation
Lightning
Small OM uptake
Soil Organic Matter
Mineralization
NH4
NO3-
NO2
Nitrification
N2O
NOx
Aerobic
Soil Organic Matter
NH4
Mineralization
Denitrification
Anaerobic
Leaching
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Long-term experimental plots
Fertilizer added as NH4NO3 at the beginning of
the growing season (early June) Added 10g N,
5g P m-2 y-1 for 20 years ? 200 g m-2 total N
added
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Mack et al, 2004 Nature
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Fertilized / non-fertilized (CT) tundra (heath)
plots
Fertilized greenhouse, moist acidic tundra
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Mack et al, 2004 Nature
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C and N linkages Effects of Climate Change

• After 20 years of fertilization, C losses are
  larger than the increased C uptake, and must be
  associated with corresponding accumulation and
  loss of N
• If N remains in system, fertilization, and thus
  warming, will lead to greater C accumulation
• If N is lost, it should lead to net C loss

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Long-term fertilization of Alaskan tundra
? Where did all of the nitrogen go? ? What are
the long-term consequences for C storage?
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Simplified Soil N Cycle
Atmosphere N2
N2
N2O
NOx
Biological N fixation
Lightning
Small OM uptake
Soil Organic Matter
Mineralization
NH4
NO3-
NO2
Nitrification
N2O
NOx
Aerobic
Soil Organic Matter
NH4
Mineralization
Denitrification
Anaerobic
Leaching
(Adapted from Schlesinger 1995)
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Summary of Results

• Extrapolating the results of long-term
  fertilization to the effects of climate warming,
  denitrification could be an important N loss
  pathway in the arctic following climate-driven
  changes
• Continuing efforts to distinguish what controls
  this process and other nitrogen transformations
  will help clarify constraints on arctic ecosystem
  nutrient budgets and carbon storage abilities

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Acknowledgements
Osvaldo Sala Skylar Bayer Ben Hudson Angela
Allen Pedro Flombaum Lara Reichmann Seeta
Sistla Lucía Vivanco Jon Witman Dave Murray
Gus Shaver Anne Giblin Jim Laundre Debbie
Scanlon Christina Maki Don Burnette
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Fellowship Year - Guam

• Unincorporated Territory of the United States
• Land Area 212 square miles
• Population 154, 805 (2000 census)
• Language English and Chamorro

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Legislation

• Coral Reef Resolution (H.Con.Res. 300)
• Coastal Zone Management Act Reauthorization (
  H.R. 5451)
• Shark Conservation Act of 2008 (H.R. 5741)
• National Sea Grant College Program Act
  Reauthorization (H.R. 5618)
• Sanctuary Enhancement Act (National Marine
  Sanctuaries Act reauthorization, H.R. 6537)
• Nonnative Wildlife Invasion Prevention Act (H.R.
  6311)

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Issues

• Multinational Species Funds
• Neotropical Migratory Birds
• Aquaculture
• Wildlife Without Borders
• Illegal Wildlife Trade
• Guam Military Buildup

• International Whaling Commission
• Illegal, Unregulated, Unreported Fishing
• Oceans 21 (H.R. 21)
• Captive Primates
• Menhaden
• Invasive Brown Tree Snake

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