influences of salinity intrusion on belowground ... · • cotton strips • labile material only...

Influences of Salinity Intrusion on Belowground Decomposition: Implications for Surface

Elevation Change

Camille L. Stagg1

Nicole Cormier1, Ken Krauss1, William Conner2, Don Cahoon3

1U.S. Geological Survey, National Wetlands Research Center, Lafayette, LA2Clemson University, Baruch Institute of Coastal Ecology and ForestScience, Georgetown, SC

3U.S. Geological Survey, Patuxent Wildlife Research Center, Beltsville, MD

Sea-level Rise

River Flow Nutrients

Plant Growth

Salinity

Biomass Accumulation

Soil Redox

Sedimentation

Temperature

Surface Elevation

Subsidence

Decomposition

Waccamaw River

Savannah River

2.6 (0.16) ppt

Upper LowerMiddle Marsh

Rive

r 1Ri

ver 2

Salinity Gradient

Depth

10 25 50

Roots and Rhizomes• Litterbags• Labile and refractory materials• Long-term = 1 year• Single exponential decay model: Y= ae-kt

Cellulose• Cotton Strips• Labile material only• Short-term ~ 14 days• %Tensile strength lost

Sea-level Rise

River Flow Nutrients

Plant Growth

Salinity

Biomass Accumulation

Soil Redox

Sedimentation

Temperature

Surface Elevation

Subsidence

Decomposition

Organic Matter

Composition

• 10 cm depth• April 2011-Ocotber 2011Temperature

• 10cm, 25cm 50 cm depth• October 2010, 2011Redox

• October 2010-2011, 60 cm well depthSalinity

• Root and Rhizomes, initial material• Lignin, Cellulose, Total Carbon, Total Nitrogen

Organic Matter Composition

Soil Depth (cm)

10 25 50

% M

ass

Rem

aini

ng

0

20

40

60

80

100P = 0.7609

A A A

Soil Depth (cm)

10 25 50

Red

ox (m

V)

-300

-250

-200

-150

-100

-50

0

P = 0.5768

CSTL day-1

2.0 2.5 3.0 3.5 4.0 4.5

Soi

l Dep

th (c

m)

0

10

20

30

40

50

P < 0.0001

-505

101520253035

01-

Oct

-201

0 2

6-O

ct-2

010

20-

Nov

-201

0 1

5-D

ec-2

010

09-

Jan-

2011

03-

Feb-

2011

28-

Feb-

2011

25-

Mar

-201

1 1

9-Ap

r-20

11 1

4-M

ay-2

011

08-

Jun-

2011

03-

Jul-2

011

28-

Jul-2

011

22-

Aug-

2011

16-

Sep-

2011

11-

Oct

-201

1

Waccamaw Marsh

-10

-5

0

5

10

15

20

25

30

01-

Oct

-201

0 1

3-O

ct-2

010

26-

Oct

-201

0 0

7-N

ov-2

010

20-

Nov

-201

0 0

2-D

ec-2

010

15-

Dec

-201

0 2

7-D

ec-2

010

09-

Jan-

2011

21-

Jan-

2011

03-

Feb-

2011

15-

Feb-

2011

28-

Feb-

2011

12-

Mar

-201

1 2

5-M

ar-2

011

06-

Apr-

2011

19-

Apr-

2011

Waccamaw Lower

-10

-5

0

5

10

15

20

01-

Oct

-201

0 2

4-O

ct-2

010

16-

Nov

-201

0 1

0-D

ec-2

010

02-

Jan-

2011

25-

Jan-

2011

18-

Feb-

2011

13-

Mar

-201

1 0

5-Ap

r-20

11 2

9-Ap

r-20

11 2

2-M

ay-2

011

14-

Jun-

2011

08-

Jul-2

011

31-

Jul-2

011

23-

Aug-

2011

16-

Sep-

2011

09-

Oct

-201

1

Waccamaw Upper

-15-10-505

1015202530

01-

Oct

-201

0 2

3-O

ct-2

010

14-

Nov

-201

0 0

6-D

ec-2

010

28-

Dec

-201

0 1

9-Ja

n-20

11 1

0-Fe

b-20

11 0

4-M

ar-2

011

26-

Mar

-201

1 1

7-Ap

r-20

11 0

9-M

ay-2

011

31-

May

-201

1 2

2-Ju

n-20

11 1

4-Ju

l-201

1 0

5-Au

g-20

11 2

7-Au

g-20

11 1

8-Se

p-20

11 1

0-O

ct-2

011

Waccamaw Middle

Time (Days)

0 100 200 300 400

% M

ass

Rem

aini

ng

60

70

80

90

100

110

UpperMiddleLowerMarsh

P<0.0001

P=0.0203

AA

A

B

Landscape Salinity Gradient

Upper Middle Lower Marsh

% M

ass

Rem

aini

ng

0

20

40

60

80

100



Sal

inity

(ppt

)

0

1

2

3

4

P < 0.0001

SalinityA

B

C

D



Soi

l Tem

pera

ture

( C

)

0

5

10

15

20

25

30

35

P = 0.0856

Soil Temperature



Red

ox (m

V)

-300

-250

-200

-150

-100

-50

0

Redox

P = 0.0663

Salinity (ppt)

0 1 2 3 4 5

% M

ass

Rem

aini

ng

40

50

60

70

80

90

100

r = 0.38309P = 0.1430

Pearson Product-Moment Correlations

Redox Potential (mV)

Temperature(°C)

PorewaterSalinity (ppt)

% Mass Remaining r = -0.18041P = 0.5037

r = 0.47682P = 0.2322

r = 0.38309P = 0.1430

P=0.0203

AA

A

B



% M

ass

Rem

aini

ng

0

20

40

60

80

100

> 3ppt

Site Lignin Cellulose Carbon : Nitrogen Lignin : Nitrogen

Upper 35.1 (3.9) a 20.3 (0.9) bc 44.5 (1.2) bc 35.8 (1.5) b

Middle 34.9 (0.6) a 22.4 (0.9) ab 48.7 (3.8) b 38.6 (2.9) a

Lower 26.5 (6.0) b 18.0 (1.7) c 41.1 (0.9) c 29.0 (3.4) d

Marsh 22.3 (1.3) b 24.2 (0.5) a 61.6 (2.9) a 32.0 (3.1) c

Different letters indicate significant differences between site/salinity treatments



CS

TL d

ay-1

0

1

2

3

4

5

C

B

A

B

P < 0.0001

• Sulfate Introduction – Stimulated respiration– C- mineralization: Weston et al., 2011; Weston et al., 2006

• Nitrogen Availability– Salinity-induced plant mortality or stress with subsequent nutrient

pulse, or lower Nitrogen uptake and increased Nitrogen availability.

Pearson Product-Moment Correlations (n=120)

Total sulfur Conductivity

N mineralization flux(µmol m-2 d-1)

r = -0.088P = 0.338

r = -0.076P = 0.412

N turnover(d-1)

r = 0.017P = 0.852

r = 0.055P = 0.551

Noe et al., in review

Salinity (ppt)

0 1 2 3 4 5

CS

TL d

ay-1

12

14

16

18

20

22

24

26

28

Pearson Product-Moment Correlations

Redox Potential (mV)

Temperature(°C)

PorewaterSalinity (ppt)

CSTL day-1 r = -0.03203P = 0.9063

r = 0.39566P = 0.3319

r = 0.08374P = 0.7578

r = 0.08374P = 0.7578

NutrientsPlant

Growth/Mortality

Salinity Decomposition+- +

+



% M

ass

Rem

aini

ng

0

20

40

60

80

100



CS

TL d

ay-1

0

1

2

3

4

5

CB

A

B

Refractory + Labile Labile

A A AB

> 3ppt

N

Primary Production

Decomposition



Ele

vatio

n C

hang

e (c

m)

0

1

2

3

4

Accretion Surface Elevation Change

SLR 0.3 - 0.4 cm y-1

Time (year)

0.0 0.5 1.0 1.5 2.0

Sur

face

Ele

vatio

n C

hang

e (c

m)

-1

0

1

2

3

4

Upper MiddleLowerMarsh

P < 0.001

• Decomposition of refractory organic matter is limited when salinity exceeds 3ppt.

• There is not effect of salinity on decomposition of refractory material between 0-3ppt

• Decomposition of labile organic matter is stimulated in the degraded forest. Stimulation may be due to nutrient pulse/ increased nutrient availability resulting from salinity-induced plant mortality or stress.

• Decomposition of labile organic matter is limited in the marsh, either from adverse impacts of salinity on microbial activity or lack of nutrient availability.

• Marsh elevation is increasing and likely due to a combination of decreased organic matter decomposition and increased primary production.

influences of salinity intrusion on belowground ... · • cotton strips • labile material only...

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