Developing a tool to classify and map factors limiting plant growth in coastal marshes

J. Andy Nyman, Vanessa D. TobiasSchool of Renewable Natural Resources, Louisiana State University Agricultural Centerjnyman@lsu.edu

John D. Foret, Joy J. MerinoNational Marine Fisheries Service

Ron D. DeLauneDepartment of Oceanography and Coastal Sciences, Louisiana State University

Dayna HuvalDepartment of Biology at the University of Louisaina at Lafayette

image: 19 April 2008, NASA Stennis Space Center Aeronet Network

Nyman et al. 2006 Estuarine Coastal and Shelf Science. 69:370-380.

DeLaune et al. 1990. Catena 17:277-288

Maybe the limiting factor is salinity stress.

Maybe the limiting factor is nutrient availability.

Mapping the Factors Limiting Growth of Existing Emergent Wetland Vegetation in Coastal Louisiana: flooding stress, salinity stress, nutrient limitation

• understand why existing restoration projects are having the effects that they do

• adaptively manage existing restoration projects that have water control structures such as diversions, marsh management, etc.

• more accurately predict the effects of restoration alternatives

• The ability to map limiting factors in agricultural crops has been routine for decades.

• The ability to map limiting factors in coastal wetlands is new:– Spartina patens. Most common plant in coastal

Louisiana

Mapping the Factors Limiting Growth of Existing Emergent Wetland Vegetation in Coastal Louisiana: flooding stress, salinity stress, nutrient limitation

A Tool for Identifying Limiting Factors

• collect 5 grams (about half a sandwich-sized ziplock bag) of “newest fully developed leaves

• if in plastic, then store on ice• if in paper, then no ice needed

• oven-dry the leaves• grind the dried leaves• arrange for leaves to be analyzed for “Plant Environmental plus C and N” by the Soil Testing and Plant Analyses Laboratory (STPAL) at the LSU AgCenter• mail samples and $16/sample to STPAL• use results to classify sample as flood-limited, salinity-limited, nitrogen-limited, or co-limited

using chemical content of S. patens leaves to classify limiting factors

1. Is the Mn content less than 223 ppm?

a) if yes, then classify the site as flood stressed

b) if no, then proceed to step 2

[Na]%

0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4

Mol

ar C

:N R

atio

40

45

50

55

60

65

70

75

Nutrients Both

Neither Salinity

technical documentationMerino, J., D. Huval, and J. Nyman. in press. Implication of nutrient and

salinity interaction on the productivity of Spartina patens. Wetlands Ecology and Management.

Tobias, V.D., J.A. Nyman, R.D. DeLaune, and J.D. Foret. in press. Improving marsh restoration: leaf tissue chemistry identifies factors limiting production in Spartina patens. Plant Ecology.

Tobias, V.D. J.A. Nyman, and J.D. Foret. in review. Developing critical values to improve diagnosis and management of flooding stress in marshes dominated by Spartina patens.

Tobias, V.D. J.A. Nyman, and J.D. Foret. in preparation. Field trials of critical values to identify flooding stress, salinity stress, and nutrient

limitation in marshes dominated by Spartina patens.

Next Step

• Find funding to produce the first map using these tools. Potential areas include– Management:

• Caernarvon outfall (roughly estimated at $150,000 in 2008)

• Cameron-Creole Watershed

– Planning• White Ditch

• South Pecan Island

Andy Nyman, 578-4220, jnyman@lsu.edu or jnyman@agcenter.lsu.edu School of Renewable Natural Resources, Louisiana State University Agricultural Center

Developing a tool to map limiting factors to coastal wetland vegetation

1. grow plants under controlled salinity and nutrient conditions– develop chemical signatures for plants growing all four possible conditions:

salinity-limited, nitrogen-limited, co-limited, and unlimited conditions

2. grow plants under controlled flooding and known salinity and nutrient conditions– develop chemical signatures for plants growing in all eight possible conditions:

salinity-limited, nitrogen-limited, flood-limited, salinity & nitrogen limited, nitrogen and flood-limited, salinity and flood-limited, tri-limited, and unlimited conditions

3. challenge/validate chemical signatures with new data from the field

1. pre-CREST greenhouse study

H0: Aboveground and belowground biomass of S. patens will not differ among salinity and nutrient treatments.

1populations # 66 and # 81 described by Hester et al. 1996. American Journal of Botany 83: 1521-1527.

Factors N Levels

salinity (ppt) 4 2, 6, 18, 36

soil nutrients (% of average) 4 25, 75, 125, 200

tubs within each salinity/nutrient combination

4

populations1 within tubs 2

total 128

1. pre-CREST greenhouse study

stress factor

0 1 2 3 4

plan

t gro

wth

0

25

50

75

100

125

150

stress factor

0 1 2 3 4

plan

t gro

wth

0

25

50

75

100

125

150

stress factor

0 1 2 3 4

plan

t gro

wth

0

25

50

75

100

125

stress factor

0 1 2 3 4

plan

t gro

wth

0

25

50

75

100

125

150

175

200

salinity stress more important than nutrient availability

nutrient availability more important than salinity stress

interaction: nutrient availability negates salinity stress

interaction: salinity stress negates nutrient availability

Target Salinity (ppt)

0 5 10 15 20 25 30 35 40

Bio

mas

s (g

/pot

)

0

20

40

60

80

100

120

140

160

30% N, 125%P95% N, 375% P130% N, 620% P205% N. 980% P

interaction: salinity stress negates nutrient availability

stress factor

0 1 2 3 4

plan

t gro

wth

0

25

50

75

100

125

150

175

200

1. pre-CREST greenhouse study

average water salinity

0 5 10 15 20 25 30 35 40

pote

ntia

l bio

ma

ss (

%)

0

25

50

75

100high nutrient availability

average nutrient availabilitylow nutrient availability

stress factor

0 1 2 3 4

plan

t gro

wth

0

25

50

75

100

125

150

175

200

average water salinity

0 5 10 15 20 25 30 35 40

pote

ntia

l bio

ma

ss (

%)

0

25

50

75

100high nutrient availability

average nutrient availabilitylow nutrient availability

Target Salinity (ppt)

0 5 10 15 20 25 30 35 40

Bio

mas

s (g

/pot

)

0

20

40

60

80

100

120

140

160

30% N, 125%P95% N, 375% P130% N, 620% P205% N. 980% P

Neither

Nutrient Both

Salinity

1. pre-CREST greenhouse study

Limiting Factor

Neither Nutrients Salinity Both

Mo

lar

C:N

Rat

io

0

20

40

60

80

100

120

High Nutrients

Low Nutrients

Limiting Factor

Neither Nutrients Salinity Both

[Na]

%0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

Low Salinity

High Salinity

1. pre-CREST greenhouse study

[Na]%

0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

Mol

ar C

:N R

atio

0

20

40

60

80

100

120NeitherNutrientsSalinityBoth

CREST-funded study

[Na]%

0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4

Mol

ar C

:N R

atio

40

45

50

55

60

65

70

75

Nutrients Both

Neither Salinity

Grow Plants Under Controlled Flooding and Known Salinity & Nutrient Conditions

• use marsh organs to create a range of flooding stress

• place marsh organs is areas with different salinity and nutrient conditions

high salinity

low salinity

Grow Plants Under Controlled Flooding and Known Salinity & Nutrient Conditions

Grow Plants Under Controlled Flooding and Known Salinity & Nutrient Conditions

develop chemical signatures for plants growing in all eight possible conditions

develop chemical signatures for plants growing in all eight possible conditions

CREST-Funded:Field Study

• challenge/validate the leaf-tissue tool using leaf tissue and porewater samples collected across the coast of Louisiana

• compare predictions of limiting factors based on landscape features to those identified by the leaf-tissue tool

• Biomass– 0.25m2 clip plots

• Porewater– YSI- pH, conductivity, salinity, temperature– Hach Colorimeter- Ammonia-N, Ortho-

Phosphate

• Tissue Stoichiometry– ICP: Na concentration– CHN Analyzer: C and N content

CREST-Funded:Field Study

low nutrients

high nutrients

CREST-Funded:Field Study

high salinity

low salinity

low nutrients

high nutrients

CREST-Funded:Field Study

high salinity

low salinity

Por

ewat

er A

mm

onia

(m

g/L)

0

2

4

6

8

10

12

14

16

18

20

22

24

26DBBHBCPSGHIMIAMIFWMISWMRB

Spring SpringSummer SummerFall Fall

2007 2008

Por

ewat

er O

rtho

phos

phat

e (m

g/L)

0

2

4

6

8

10

12

14

16

18

20

22

24

26 DBBHBCPSGHIMIAMIFWMISWMRB

Spring SpringSummer SummerFall Fall

2007 2008

Por

ewat

er S

alin

ity (

ppt)

0

2

4

6

8

10

12

14

16

18

20

22

24

26

DBBHBCPSGHIMIAMIFWMISWMRB

Spring SpringSummer SummerFall Fall

2007 2008

CREST-Funded:Field Study

good news: leaf-tissue signatures developed in the experiments worked in the field; i.e.,

limiting factors identified via tissue analyses match nutrients and salinity measured in the

field via pore water

CREST-Funded:Field Study

low nutrients

high nutrients

high salinity

low salinity

bad news: pore water analyses proves that even simple predictions such as this regarding landscape position, nutrient

availability, and salinity are wrong

Por

ewat

er A

mm

onia

(m

g/L)

0

2

4

6

8

10

12

14

16

18

20

22

24

26DBBHBCPSGHIMIAMIFWMISWMRB

Spring SpringSummer SummerFall Fall

2007 2008

Por

ewat

er O

rtho

phos

phat

e (m

g/L)

0

2

4

6

8

10

12

14

16

18

20

22

24

26 DBBHBCPSGHIMIAMIFWMISWMRB

Spring SpringSummer SummerFall Fall

2007 2008

Por

ewat

er S

alin

ity (

ppt)

0

2

4

6

8

10

12

14

16

18

20

22

24

26

DBBHBCPSGHIMIAMIFWMISWMRB

Spring SpringSummer SummerFall Fall

2007 2008

CREST-funded conclusions• Stoichiometry of leaf tissue can be used to map

flooding stress, salinity stress, and nutrient limitation in S. patens.

• Field trial of this tool reflected– seasonal differences in flooding stress, salinity stress,

and nutrient availability

– annual differences in flooding stress, salinity stress, and nutrient availability

– spatial patterns in flooding stress, salinity stress, and nutrient availability that challenge of even simple, landscape-scale attempts to predict nutrient availability and salinity stress

• collect 5 grams (about half a sandwich-sized ziplock bag) of “newest fully developed leaves

• if in plastic, then store on ice• if in paper, then no ice needed

• oven-dry the leaves• grind the dried leaves• arrange for leaves to be analyzed for “Plant Environmental plus C and N” by the Soil Testing and Plant Analyses Laboratory (STPAL) at the LSU AgCenter• mail samples and $16/sample to STPAL• use results to classify sample as flood-limited, salinity-limited, nitrogen-limited, or co-limited

CREST-funded study:A Tool for Identifying Limiting Factors

[Na]%

0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4M

olar

C:N

Rat

io

40

45

50

55

60

65

70

75

Nutrients Both

Neither Salinity

average water salinity

0 5 10 15 20 25 30 35 40

pote

ntia

l bio

ma

ss (

%)

0

25

50

75

100high nutrient availability

average nutrient availabilitylow nutrient availability

Questions

CREST-funded study

average water salinity

0 5 10 15 20 25 30 35 40

pote

ntia

l bio

ma

ss (

%)

0

25

50

75

100high nutrient availability

average nutrient availabilitylow nutrient availability

cc

b

a

DeLaune et al. 2005 Wetlands 25:155-161

average water salinity

0 5 10 15 20 25 30 35 40

pote

ntia

l bio

ma

ss (

%)

0

25

50

75

100high nutrient availability

average nutrient availabilitylow nutrient availability

ref

man

ref+fert

man+fert

Foret. 2001. PhD Dissertation. University

of Louisiana at Lafayette.