Significant seasonal and event-driven changes of carbon and nutrient fluxes to first-order streams of an Amazon forest
Mark S. Johnson, Johannes Lehmann, Evandro Carlos Selva, Eduardo Guimarães Couto, Mara Abdo, Erick C.M. Fernandes,
Susan Riha
Cornell UniversityUniversidade Federal do Mato Grosso
Why study tiny catchments?
Clearly reflect land surface processesImportant measurements for determining
C balances and fluxes across interfacesOnce you get a bit (~50 m) downstream,
instream processes begin to strongly influence the aquatic picture
Site Description
Four perennial headwater catchments
Small streams originating as seeps (minas d’agua ou nacentes)
Juruena, MT
0.85 Ha1.69 Ha0.78 Ha0.62 Ha
N0 50 100 Meters
1
2
3
4 IKONOS Panchromatic Image(Courtesy EOS-Webster)
Headwater watersheds
1
234
0.85 Ha1.69 Ha0.78 Ha0.62 Ha
N0 50 100 Meters
1
2
3
4 IKONOS Panchromatic Image(Courtesy EOS-Webster)
Headwater watersheds
1
234
Jun-03 Aug-03 Oct-03 Dec-03 Feb-04 Apr-04 Jun-04
0
100
200
mm
d-1 throughfall
Site Description
Four perennial headwater catchments
Small streams originating as seeps (minas d’agua ou nacentes)
Juruena, MT
May-03 Jul-03 Sep-03 Nov-03 Jan-04 Mar-04 May-04
4.5
5.0
5.5
6.0
6.5
7.0
Streamwater pH- Seasonal Dynamics As dry season
progresses, streamflow pH rises.
Hypothesis: High GPP during rainy-season leads to higher soil CO2, and lower ground-water and stream water pH.
n=4 watersheds
100
mm d-1
Jul 03 Sep 03 Nov 03 Jan 04 Mar 04 May 04
Co
nd
uct
ivity
(S
cm
-1)
0
20
40
60
80
100
1200
100
Electrical Conductivity- Seasonal Dynamics As dry
season progresses, streamflow becomes more concentrated
Streamflow becomes more dilute as rainy season progresses.
n=4 watersheds
Carbon fluxes to forest floor
Sep-03 Oct-03 Nov-03 Dec-03 Jan-04 Feb-04 Mar-04 Apr-04
Litt
erfa
ll (g
C /
m2 )
and
Thr
ough
fall
(g C
/ m
2 )
0
25
50
75
100
Litter (g/m^2) TF (g/m2)
For period presented, 23X more C fell as litter than as DOC in throughfall
Selva et al., 2004 LBA poster 27.7-P for C in litterfall fractions
Mean ± SE, n=4 watersheds
DOC concentrations in surface runoff (enchurrada) Litter build up
during dry season leads to very large DOC values for surface runoff
Throughfall-DOC followed a similar pattern
01-Sep-03 01-Nov-03 01-Jan-04 01-Mar-04 01-May-04
0
100
200
0
10
20
30
40
50
60
70
DO
C (
mg
L-1)
Surface ponding- late in wet season
Rainfall-discharge-DOC flux relationship
DOC flux Discharge
Ra
infall (m
m d
-
1)
01-Sep-03 01-Nov-03 01-Jan-04 01-Mar-04 01-May-04
0
100
200
0
100
200
300
Dis
char
ge (
x 1
03 L
da
y-1)
and
DO
C fl
ux (
g d
ay-1
)
Ra
infall (m
m d
-1)
DOC stream export Discharge (vazão)
High surface DOC concentrations during dry to wet transition leads to high DOC export
Lower surface DOC concentrations during late rainy season leads to lower DOC export
Baseflow and storm flow DOC DOC (mg/L)
Baseflow Storm flow Ratio
Oct-03 5.7 10.0 1.7
Nov-03 3.1 9.9 3.2
Dec-03 2.4 7.5 3.1
Jan-04 2.1 7.3 3.5
Feb-04 1.9 5.8 3.1
Mar-04 1.1 3.6 3.3
Apr-04 0.7 3.8 5.3
Baseflow and storm flow CPOC
Intact leaves transported during baseflow
Fragmented material transported during storm flow
Evandro Selva et al., 2004, LBA poster 27.7-P
Rapid surface runoff, rapid stream response
Overland flow present
Percolation present at 10 cm
13:00 14:00 15:00 16:000
20
Ra
infall (m
m) p
er 5 m
inu
tes
0
10
20
Discharge
rainfall D
isch
arge
(L
s-1)
Time of Day, 28 April 2004
24 April 2004, Watershed 4
12:00 13:00 14:00 15:00 16:00 17:00
pHD
O (
mg
L-1)
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
EC
( S
cm
-1)
0
5
10
15
20
25
30
pH Dissolved OxygenElectrical Conductivity
Storm dynamics- pH, DO, EC
Storm water shows initial surficial contribution
Then, increasing contribution of subsurface lateral flow More anoxic More acidic More dilute
Groundwater seeps pH = 4.56 EC = 7 µS cm-128 April 2004, Watershed 2
pH Dissolved OxygenElectrical Conductivity
CO
2(aq
) pp
m
Lateral flow delivering CO2 pulse
28 April 2004, Watershed 2 12:00 13:00 14:00 15:00 16:00 17:00
Dis
char
ge (
L s-1
)
-1)
0
10
20
0
2000
4000
6000
8000
Discharge CO2(aq)
CO
2 (aq) p
pm
Initial CO2 decrease due to surface contributions
Storm water pulse of free CO2 flushed out of soil profile with interflow (rapid subsurface flow)
Terrestrial-aquatic organic C flux
DOC84.6%
POC12.1%
CPOC3.3%
DOC84.6% POC
12.1%
CPOC3.3%
Jan - May 2004
Dissolved C exports are 5.5X solid C exports
Large losses of CO2 from emergent groundwater
Forested Ultisol-OxisolSouthern Amazon, Juruena, MTN=30(from 4 watersheds)
Distance from spring (m)
0 20 40 60 80 100 120 140 160 25000
5000
10000
15000
20000
25000
30000
35000
y=24489.9/(1+0.1189X)r=0.79
pC
O2 (
pp
m)
Johnson et al. (unpublished data)
Terrestrial-aquatic C flux components
Jan - May 2004
DOC6.6%
HCO3- C15.7%CO2-C(aq)
10.5%
CO2-C outgas evasion66.0%
CPOC0.3%
POC0.9%
Solid Phase1.2%
Conclusions Solid inputs >> dissolved inputs Gaseous outputs >> dissolved outputs >> solid
outputsAboveground DOC fluxes become more dilute
over the course of the wet season If soil DOC are in equilibrium, aboveground fluxes are
important driver of variability within DOC system
Nested temporal scales are an important feature of the terrestrial-aquatic interface
AgradecimentosLBA and organizing committeeRohden Indústria Lígnea Ltda. for site access
and support (parabens pela sua certificação!)Jeff Richey, Alex Krusche and Paulo Nunes
for conceptual and logistical support Benedito Silveira de Andrade and Elielton
Anterio da Souza for field assistanceAo povo Brasileiro e Juruenense