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Controls of land-water nitrogen movement through small lowland forest and pasture

Controls of land-water nitrogen movement through small lowland forest and pasture drainage basins in Rondônia Christopher Neill, Linda A. Deegan, Alex V. Krusche, M. Victoria R. Ballester, Helmut Elsenbeer, Jorge M. Moraes, Reynaldo L. Victoria, Suzanne M. Thomas,

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Controls of land-water nitrogen movement through small lowland forest and pasture

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  1. Controls of land-water nitrogen movement through small lowland forest and pasture drainage basins in Rondônia Christopher Neill, Linda A. Deegan, Alex V. Krusche, M. Victoria R. Ballester, Helmut Elsenbeer, Jorge M. Moraes, Reynaldo L. Victoria, Suzanne M. Thomas, Christie L. Haupert, Adriana L. Castellanos, and Marisa C. Piccolo Marine Biological Laboratory  CENA University of Potsdam

  2. Alteration of N cycles an emerging global issue • N cycle influenced by land use • N use growing rapidly in tropics • N movement through landscapes • poorly known

  3. Most N inputs are retained in watersheds -1 Boyer et al. 2002

  4. Hypothesis: Absence of plant N limitation in Amazon forest leads to low N retention in flowpaths from terra firme to larger rivers

  5. Stream inorganic N export is low Nova Vida Rondonia 0.4 kg N ha-1 y-1 Hubbard Brook United States 1.4 kg N ha-1 y-1

  6. Terra firme Slope Riparian Stream zone NH4+ NO3- DON Soils

  7. SOILS

  8. SOILS • Low capacity for DIN retention • or loss • Low capacity for DON removal

  9. RIPARIAN ZONES Inorganic N

  10. RIPARIAN ZONES Organic N

  11. RIPARIAN ZONES • Very effective at DIN retention/ • removal • Less effective at DON retention

  12. NH4+ uptake distance Nitrification rate Nitrate uptake distance SMALL FOREST STREAM CHANNELS

  13. SMALL FOREST STREAM CHANNELS NH4+ uptake distance 1667 m NO3- uptake distance infinite % of 15N accounted for leaving reach as NH4+ 41 % of 15N accounted for leaving reach as NO3- 43 % of 15N retained in organic matter in stream channel 16

  14. SMALL FOREST STREAM CHANNELS • Convert some NH4+ to NO3- • Low retention of inorganic N

  15. Why do Amazon forest streams have low inorganic N concentrations? • Soils have low capacity to retain N • Stream channels have low capacity to • retain N • RIPARIAN ZONES are only place in • landscape where large amounts of • inorganic N are retained or removed

  16. SSNV OF TF GW Rancho Grande, RO FOREST February 19, 2003

  17. Why do Amazon forest streams have low inorganic N when soil solution N is so high? • RIPARIAN ZONES are only place in • landscape where large amounts of • inorganic N are retained or removed • Riparian N retention will depend on • hydrological connectedness • Riparian N retention will depend on soils, • basin topography, stream scale, rain event • patterns

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