Comparing Drought Response in Two Riparian Species Platanus

occidentalis L. (American Sycamore) and Salix nigra Marshall

(Black Willow) for Use in Riparian Restoration

1

Joshua Hashemi, Eric Duncan, Chelsea A. Harris, Reuben Hilliard

and Paula C. Jackson

Riparian Zones

2

American Sycamore (Platanus occidentalis)

Black Willow (Salix nigra)

3

Salix nigra

4

5

• To compare the performance of American Sycamore Platanus occidentalis L.) to Black Willow (Salix nigraMarshall) under field and greenhouse conditions.

• Determine if Arbuscular Mycorrhizae play a role in species response to water treatments.

6

Goals

AM in maize root.

7

Do Arbuscular Mycorrhizae (AM) play a role in drought

tolerance?

Overall Objectives

Field:

• Compare species in terms of:• CO2 assimilation

• Water use

• AM colonization

• Perform spore extraction from soil to ensure that homogenized field soil may be used as AM inoculum in greenhouse experiment.

Greenhouse:

• Across differing treatments of water and AM* availability, compare:• CO2 assimilation

• Anatomical growth

8

* A fungicide (Benomyl) was used to preclude AM fungal growth. All treatments had field soil as a source of

AM spore inoculum.

FIELDMATERIALS AND METHODS

(Preliminary Results)

9

CO2 assimilation and Water Use in the field

10

Amax was determined from light curves

generated using a LICOR 6400

photosynthesis system n=6 Platanus,

n=4 Salix

Water Use was determined using Thermal

Dissipation Probes (TDP)

n= 3 Platanus

n= 5 Salix

CO2 Assimilation Field

-3

0

3

6

9

12

15

0 200 400 600 800 1000 1200 1400 1600

AC

O2 (µ

mo

ls/m

2/s

)

PPFD (µmols/m2/s)

CO2 assimilation (Field)

P. occidentalis

S. nigra

11

Mean photosynthetic light curves for both species. Values represent species means (Platanus n=6, Salix

n=4). Measurements were taken in August 2013 on fully expanded leaves with healthy color and

appearance. Eric Duncan MSIB Thesis

• No significant difference in field CO2 assimilation rates.

• Differences in CO2 assimilation rates in greenhouse

experiment were expected to result from treatments

R² = 0.5905

R² = 0.4629

0

0.2

0.4

0.6

0.8

1

0 500 1000 1500 2000 2500 3000

Sa

p f

low

(g

/cm

2/m

in)

VPD Pascals

Sap flow and VPD

Salix

R² = 0.5189R² = 0.4641

0

0.2

0.4

0.6

0.8

1

0 200 400 600 800 1000

Sa

p f

low

(g

/cm

2/m

in)

PAR (µmol/m2/s)

Sap flow and Light

SalixPlatanus

12

Water use was higher in Salix and both had a strong relationship to PPFD (r =

0.68 Platanus; r = 0.72 Salix; p< 0.01) and to VPD (r = 0.68 Platanus; r = 0.77

Salix; p< 0.01)

Platanus

Mycorrhizal colonization level in field

• 10 individuals were sampled per species (20 trees total)

• Root samples were taken from a riparian area with a small (<

1 m wide) perennial stream at Kennesaw State University in

North West Georgia.

• Distance and orientation relative to the water source were

registered.

13

Field sample site – Kennesaw State University

Mycorrhizal colonization level in field

• Roots were stained with 0.05% trypan solution.

• AM Quantification was performed using the root piece

method and the root piece estimation method.

14

Colonized root stained with 0.05% Trypan BlueStaining of field samples in 0.05% trypan blue

Mycorrhizal colonization level in field

Root Piece Method:

• 160, 1cm root segments

• Root samples were checked for the presence or absence of

colonization

Root Piece Estimation Method:

• 160, 1cm root segments

• Root samples were given a

ranking based on level of

colonization

15

Root Piece Estimation

Rank % Colonization

0 0%

1 1-25%

2 26-50%

3 51-75%

4 76-100%

Field Sample Colonization Results

16

Salix nigra Colonization

Platanus occidentalis Colonization

Observed

With AM Without AM TOTAL

Platanus 28 132 160

Salix 56 104 160

TOTAL 84 236 320

Expected

With AM Without AM TOTAL

Platanus 42 118 160

Salix 42 118 160

TOTAL 84 236

CHI-SQUARED TEST

0.000374489P < 0.001

Root Piece Method:

Root Estimation Method:

Comparison of rank abundance.

Abundance was significantly higher in

Salix.

Mann Whitney U Test

P = 0.023

Soil sampling and spore extraction

• Soil samples were taken from two perennial streams

on Kennesaw State University’s campus (NW

Georgia).

• Soil was filtered through sieves and centrifuged in

sucrose solution to isolate spores.

17

Field Spore Extractions

18

Site 1 – Kennesaw State University, and spore sample

Site 2 – Kennesaw State University, and spore sample

Objectives

Greenhouse:

• Compare CO2 assimilation and anatomical

growth among species across different

treatments of AM* and water availability.

19

* A fungicide (Benomyl) was used to preclude AM fungal growth. All treatments had field

soil as a source of AM spore inoculum.

GREENHOUSEMETHODS

20

Greenhouse Experimental Design

21

A randomized complete block design was used to account for

possible microclimate differences within the greenhouse.

Treatments:

B4 A1

C3 D2

B8 A5

C7 D6

Table 2 Table 1

Letter Treatment

A Fungicide*/Wet+

B No Fungicide/Drought-

C No Fungicide/Wet

D Fungicide/Drought

* Addition of Benomyl, + Watered M/W/F, - Watered M/F

Greenhouse methods

22

Anatomical measurements:

• Plant height

• Measured with a meter stick as

• (end height – initial height) cm

• Stem width

• Measured with a caliper as:

• (end width-initial width)cm

• n=31 Platanus; n=34 Salix

• n=15-17 per treatment

Gas Exchange measurements were

taken using a Licor 6400 IRGA.

RESULTS

Greenhouse

23

24

Light Curve Model: Fungicide/Wet

Light Curve Model: No Fungicide/Drought

Light Curve Model: No Fungicide/Wet

Light Curve Model: Fungicide/Drought

Greenhouse Results –Salix Photosynthesis

25

Light Curve Model: Fungicide/Wet Light Curve Model: No Fungicide/Wet

Light Curve Model: No Fungicide/DroughtLight Curve Model: Fungicide/Drought

Greenhouse Results –Platanus Photosynthesis

Greenhouse Results –Salix anatomical

26

Greenhouse Results –Platanus anatomical

27

All visualizations created in Tableau 9.0

Conclusions - Greenhouse

• Based on Physiological Responses• Both species had similar light curves

• Further analyses may be required to distinguish treatment differences

• Based on Anatomical Results • Drought seemed to have a greater effect on Salix than on Platanus

• Platanus had a higher rate of growth

• Based on Fungicide Addition*• As seen earlier, field data showed higher colonization rates in Salix,

however Fungicide did not have as strong an effect on Salix in Greenhouse results

• Fungicide improved performance for Platanus growth under both Wet and Drought conditions.

• Possibly decreased the incidence of detrimental fungi

28

*Need to look at AM colonization in roots

Overall Conclusions

• Salix appeared to have higher water use, with

a stronger dependence on abiotic factors (VPD

and PPFD)

• Salix had stronger response to drought

• Both points may indicate a lack stomatal control?

• Our findings show that Platanus is a strong

contender for potential use in restoration

29

Acknowledgements

• Dr. Paula Jackson

• Dr. Tony Golubski

• Dr. Sigurdur Greipsson

• KSU Office of the Vice President of Research Grant

• KSU Center for Excellence in Teaching & Learning

Undergraduate Research and Creative Activity Grant

• KSU Graduate Student Association Grant

• Kennesaw State University Department of Ecology,

Evolution, and Organismal Biology

30

A Rose by any other name…

31

Signs of Fungal Rot?

32

Granier’s Equation

K= 0.0206 u0.8124

K= (ΔTmax – ΔT)/ ΔT

U= 119 x 10-6K1.231

http://www.dynamax.com

u= Mean Sap Flux Velocity

Flow= u x area

Sap flow

33