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

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180

0 10 20 30 40 50 60 70

N:P ratio

Latitude

foliar NP

litter NP

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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