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Metal Controls and Acidity Controls on
Forest Floor and B-Horizon Extractable
Phosphorus in Forested Watersheds
Michael D. SanClements1, Ivan J. Fernandez2, Stephen A. Norton3
1Dept.
of Plant, Soil, and Environmental Sciences
2Dept. of Plant, Soil, and Environmental Sciences & Climate Change Institute
3Dept. of Earth Sciences & Climate Change Institute
Research Objectives
• Apply P fractionation techniques to an analysis
of soil P, Al, and Fe across a suite of acidic
soils in forested watersheds to determine:
– chemical distributions of P among fractions
– metal controls on P availability
• Better understand influence of changing
chemical climate (e.g. acidic deposition)
ALPSS Project Sites
(Aluminum and Phosphorus in Soils and Solutions)
3
1
6
2
4
1.
2.
3.
4.
Bear Brook Watershed in Maine
Hadlock Brook Watershed
Mud Pond Watershed
Fernow Experimental Forest
5
5. Strengbach Watershed
Maine
Maine
6. Lesni Potok
Maine
West Virginia
France
Czech Republic
Conceptual Sampling Design
Stream Channel
Eight additional
sampling points
equidistant from each
other
20m
x
13 Pedons per transect
26 Pedons per watershed
10m
x
3m
x
1m
x
0.1m
x
Watershed Characteristics
• Upper B-horizon pH CaCl2: 3.4 to 4.1
• Upper B-horizon % C: 1.1 to 8.9
• Dominant Vegetation: Red spruce, Norway
spruce, American beech, European beech
• Soil Orders:
Spodosols
Inceptisols
Phosphorus Fractionation
Modified From Psenner (1985,1988)
– 1M NH4Cl
Labile-P
– NaHCO3-Na2S2O4
Reducible Fe-P
– 0.1M NaOH
Al-P, Fe-P
PT
Murphy-Riley
PT – PI =PO
– 0.5M HCl
Ca-P
– 1M NaOH
Residual-P
PI
Total Soil P by Watershed
900
d
Σ Psenner-P (mg kg-1)
800
700
acd
600
500
a
400
ca
300
eab
b
200
100
0
EB
HB
MP
F4
LP
SB
Distribution of P by Fraction
Residual-P
14%
Labile P
1%
Fe-P
4%
Ca-P
9%
Al-P
72%
pH, Al, and P
40 100
1400
80
0
0
30
1200
PNaOH-25
1000
60
HB800
MP
F3 600
F4
SB 400
LP
EB200
WB
20
40
10
20
3.0
0
3.03.2
3.4
3.6
3.5
3.8
4.0
4.0
4.2
pH CaCl
pH CaCl
2
2
4.44.5 4.6
4.8 5.0
AlNaOH-25 mmoles kg-1
PNaOH-25 mmoles kg-1
Al(NaOH-25):P(NaOH-25)
AlNaOH-25
Linkages to Biology?
B-horizon Controls on Forest Floor P
Mean O-horizon P(NH4Cl) mg kg
-1
200
SB
MP
F3
F4
EB
WB
180
160
140
120
100
80
60
40
20
0
10
20
30
40
Mean Al(NaOH-25):P(NaOH-25)
50
60
Conclusions
1. The results suggest that Al controls P accumulation,
and that Al dynamics are an important control on the
biological availability of P
2. Any process or perturbation affecting Al within the
ecosystem could directly alter P dynamics
Acknowledgements
With special thanks to:
•Mary Beth Adams, U.S.D.A Forest Service
•Tom Navratil, Czech Geologic Society
•Marie-Claire Pierret, University of Strasbourg
•Cheryl Spencer, University of Maine
•David Manski, National Parks Service
This research supported by:
National Science Foundation
Maine Agricultural and Forest Experiment Station