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Key connections in Amazonian Key connections in Amazonian stream corridors: Using stream corridors: Using 1515N to N to trace N transformations and trace N transformations and transport transport
ND-03: Deegan, Neill, Victoria, Krusche, Ballester, Gessner, Haupert, Thomas
UPLAND
SMALLSTREAM
RIPARIAN
LARGE RIVERS
SLOPE
FOREST TO PASTURE FOREST TO PASTURE CONVERSIONCONVERSION
• dissolved nutrients & nutrient ratios,
• stream conditions (e.g., oxygen) and
• biota (e.g., increased algae, loss of invertebrates in pastures)
N & P processing affected by changes in:
KEY QUESTIONSKEY QUESTIONS
• How and at what rates is nitrogen How and at what rates is nitrogen transformed in tropical forest streams?transformed in tropical forest streams?
• How does conversion to pasture alter N How does conversion to pasture alter N cycle?cycle?
• How far and in what form is nitrogen How far and in what form is nitrogen transported? transported?
FATE AND TRANSFORMATION OF NITROGENFATE AND TRANSFORMATION OF NITROGEN
15N NH4
+ UPTAKE
-10 0 30 40 50 60 80 800
Downstream Distance (m)> > >
Measure 15N of 15NH4+,
15NO3- and organic matter (including biota)
1515N Addition SchematicN Addition Schematic
2
4
3 5 68
Dripper
1
15N
STREAM
FLOW
79
Add 15(NH4)2SO4 for 21 days to raise the 15N of stream NH4
+
Conversion to other components
15N
of N
H4+
DISTANCE (M)
UPTAKE LENGTH - NHUPTAKE LENGTH - NH44++
0
100
200
300
-100 100 300 500 700
Day 1Day 21
3000m
1000m
Temperate Stream ~50m
0
100
200
300
d1
5N
-20 280 580 880
m_down_plot
NO3NH4
Bivariate Line ChartSplit By: TypeInclusion criteria: A Nh4/no3/day from Br Forest 15N.stv
0
50
100
150
d1
5N
-20 280 580 880
m_down_plot
NO3NH4
Bivariate Line ChartSplit By: TypeInclusion criteria: A Nh4/no3/day from Br Forest 15N.stv
Day 1 Day 21
DISTANCE (M)
0
100
200
300
d15N
-20 280 580 880
m_down_plot
NO3NH4
Bivariate Line ChartSplit By: TypeInclusion criteria: A Nh4/no3/day from Br Forest 15N.stvNITRIFICATION RATENITRIFICATION RATE
15N
RATE: ~5 X 10-6 m-1 or 2 x 10-5 ug/m2/min
~10% of NH4 loss converted to NO3
Temperate TropicalWalker Branch, TN Nova Vida, RO
NH4+ uptake length (m) 30 2000
NO3- uptake length (m) 500 infinite
Nitrification rate (1/m) 10-3 10-6
FOREST STREAM FOREST STREAM COMPARISIONCOMPARISION
% of 15N added Temperate TropicalWalker Branch Nova Vida
Retained 48 2
Total export 31 69
FOREST STREAM N MASS FOREST STREAM N MASS BALANCEBALANCE
NO3 23 8
NH4 4 60
Particulate 4 1
Effect of conversion to Effect of conversion to pasture?pasture?
0
500
1000
1500
-200 0 200 400 600
NO3
NH4
Small pasture stream
0
200
400
600
800
-100 100 300 500 700
NO3
NH4
Larger pasture stream
15N
Ammonium uptake length is shorter
(~500m)
Nitrification rate is near zero
For the rest of the story – see the poster Haupert 37.5
NHNH44++ uptake length is 10 to 100 times uptake length is 10 to 100 times
longer than in temperate streamslonger than in temperate streams
Peterson et al. 2001
TROPICAL FOREST STREAM
At 40 L s-1
TropicalForest: 2000mPasture: 500m
TemperateForest: 50 m
PASTURESTREAM
New Knowledge New Knowledge
• Not like temperate forest streams– Little transformation of DIN
• Low rates of nitrification• Little storage; Low rate of N release from
stream bottom
– Little retention of N occurs• Long downstream transport > 1000’s m • Primarily as DIN• Function as conduits that transport N from
upper reaches of watersheds to larger rivers.
New KnowledgeNew Knowledge
• Pasture formation radically alters N transformation and transport
– Nitrification is near zero in pasture streams
– NH4+ uptake length is shorter (500m) than
in tropical forest (2000m)
….. but still 10X longer than temperate forest
(50m)
SYNTHESIS & SCALINGSYNTHESIS & SCALINGSynthesis of stream N, P Synthesis of stream N, P and C processes across and C processes across different soil types and different soil types and regionsregions
Develop a model to Develop a model to integrate land use mosaic integrate land use mosaic with stream chemistry, with stream chemistry, stream size, riparian area stream size, riparian area and hydrology to predict and hydrology to predict the export of materials to the export of materials to larger rivers.larger rivers.