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Hydrologic losses from tropical forest soils– patterns and implications
Lars O. Hedin, Megan McGroddy, Ben Houlton, Emilio Moran and Mateus Battisella
LC-09
To determine the biological and physical (climate and geological) controls over patterns of nutrient losses from lowland Amazonian forest ecosystems
Justification
Carbon cycling is constrained by availability of biologically essential nutrients
Goal
0
20
40
60
80
100
120
140
160
180
0 10 20 30 40 50 60 70
N:P ratio
Latitude
foliar NP
litter NP
0
200
400
600
800
1000
1200
1400
2000
3000
4000
DON
NO3-
NH4-
S Temperate North America
Hawaii Other Tropical
Approach
Extensive sampling
Mature or undisturbed forests to determine “baseline” conditions
denitrification
occlusion
deposition
ground water inputs
Research Approach
1st phase
Determine impact of seasonality on nutrient concentrations and ratios
2nd phase
Extend sampling to include a wider range of sites
1st phase sites
pH C N Basal area
Prod.
t ha-1 yr-1
N
(%)
Altamira 5.2 1.46% 0.20 % 50 nd nd
Santarem 4.2 2.26 % 0.17 % 24.4 5.57 1.9-2.9%
Manaus 4.4 1.0 % 0.07% 5.42 1.78%
Soils Leaf litter
Altamira data from Moran et al. 2000 , Lu et al. 2002
Santarem data from Silver et al. 2000, Williams et al. 2002, Silver pers. comm.
Manaus data from Luizão 1989, Luizão et al 2004
Results
Manaus dryManaus wet
Altamira dry
Altamira wet
Santarem dry
Santarem wet
0.01
0.1
1.0
10.0
Mg
( p
pm
)
Altamira Santarem Manaus
0.01
0.1
1.0
10.0
Ca
(pp
m)
Altamira Santarem Manaus
0.01
0.1
1.0
10.0
0 2 4 6 8 10 12
Ca
pp
m
Cl ppm
Seasalt Cl:Ca ratio
0.0001
0.001
0.01
0.10
1.00
10.00N
O3-
N p
pm
Altamira Santarem Manaus
0.1
1
10T
ota
l P (
pp
b)
Altamira Santarem Manaus
1
10
100
1000T
N:T
P r
atio
Altamira Santarem Manaus
Inorganic NOrganic N
Altamira Santarem Manaus
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8N
co
nc
en
trat
ion
(p
pm
)
wells and lysimeters
0
200
400
600
800
1000
1200
1400
2000
3000
4000
DON
NO3-
NH4-
S Temperate North America
Hawaii
Brasil
Other Tropical
Hawaii Mainland
Mean Annual Precipitation (mm)
2000 2500 3000 3500 4000 4500 5000
15
N o
f T
DN
(p
er
mil
vs. a
ir)
-4
-2
0
2
4
6
8
10
Maui Forest Rainfall GradientInputs
Streams
N Fixation15 N
of
TD
N (
per
mil
vs.
air
)
-4
-2
0
2
4
6
8
10
Further goals
Expand the sampling gradient in Brasil both in terms of geographic expanse and variability of state factors of interest
Incorporate measures of biotic productivity and nutrient demand into analyses
Include 15N and 18O analyses to determine the importance of denitrification pathways in these sites
Many thanks to:
Chico Aves, Jo Bahiano, Niro Higuchi, Flavio Luizao, and the LBA Support Staff in Santarém and Manaus