What to do with all our data?Tomomi Suwa and Liz Schultheis

GK-12 Workshop Session

DiversityProductivityCoexistence

Nutrients and Productivity

• Proteins, enzymes, metabolic processes, part of chlorophyll

• Plants grow larger and produce more seeds and fruits

Nutrients and Productivity in Plant Functional Groups

• While plants benefit from fertilization, not all plants will benefit to the same extent.

Nutrients and Productivity in Grass

• Grass species are notorious for needing high levels of nitrogen fertilizers

• They grow quickly and are browsed commonly by insects and mammals

Nutrients and Productivity in Legumes

• Legume plants have rhizobia bacteria living in their roots, helping them fix nitrogen

Nutrients and Productivity in Forbs

• Forbs = broad leaved, non-woody non-grass species. Commonly found in old fields and meadows.

• Forbs are a very diverse and variable group of plants

• Some forbs have high nitrogen requirements, while other require very little

Nutrients and Diversity

• If fertilization affects different groups of plants in different ways, what do you predict fertilization will do to species richness (# species)?

Our Questions:• How does nutrient addition

affect diversity and productivity?

• Does nutrient addition affect diversity and productivity of groups of plants in different ways?• Grasses• Legumes• Forbs

• Experimental design of schoolyard plots parallels the T7 treatment at the KBS LTER.

• Successional fields with a diversity of grass, legume, and forb species.

• Nitrogen fertilizer addition treatment.

• Every year collect subset of biomass to determine plant productivity.

• Measure the diversity of species.

What are the equivalent treatments in the BEST plots?How does fertilization affect diversity/productivity?

LTER Data Set

• 5 sheets• Raw data• Richness 2003 Data• Biomass 2003 Data• Richness over time (1989-2003)• Biomass over time (1989-2003)

Go to excel spread sheets:

What specific questions can we ask?

Our Question:Do grasses and legumes respond differently to N

addition? What do you predict?

-richness-biomass

We’ll address this question as a group!

Do grass and legume respond differently to

N addition? Break into 4 groups1. Grass Richness2. Grass Biomass3. Legume Richness4. Legume Biomass

Forb Biomass

Our Question:

10

20

40

60

80

100

120

140

160

180

No N Addition

N Addition

e.g. How did forbs respond to Nitrogen addition?

Forb

Bio

mas

s (g) SE

SE Average

To calculate Standard Error (SE):

-Two-step process

€

Variance =(x − x )2∑n −1

€

SE =Var

n

=var (A1:A6)

=sqrt (var(A1:A6))/# replicates)

Let’s go to Excel and graph the data

Data from year 2003

10

20

40

60

80

100

120

140

160

180

No N Addition

N Addition

e.g. How did forbs respond to nitrogen addition?

Forb

Bio

mas

s (g)

How can we tell the difference??

Analyze the data with T-test

• Used to determine if two groups are considered different

10

20

40

60

80

100

120

140

160

180

P-value• The p-value tells whether or not two groups

are different

10

20406080

100120140160180

N- N +

If p ≤ 0.05, two groups are differentIf p > 0.05, two groups are NOT different

e.g. p=0.013

Let’s go to Excel to do t-test!

4 groups:Grass RichnessGrass BiomassLegume RichnessLegume Biomass

What did you find?

12.2

2.25

2.3

2.35

2.4

2.45

2.5

2.55

N-N+

10

0.5

1

1.5

2

2.5

3

N-N+

Graphs: Richness and Biomass 2003Grass Legume

Rich

ness

10

5

10

15

20

25

N-N+

102468

1012141618

N-N+

Biom

ass

(g)

Does the effect of N fertilization change over time?

e.g. forb biomass

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

0

20

40

60

80

100

120

140

160

180

N-N+

Forb

bio

mas

s (g)

Year

Does effect of N change over time?

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

0

20

40

60

80

100

120

140

160

180

N-Linear (N-)N+Linear (N+)

Is this pattern real??

Forb

bio

mas

s (g)

Year

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

0

20

40

60

80

100

120

140

160

180

N-Linear (N-)N+Linear (N+)

Does effect of N change over time?

• Plot scatter graph

Is this pattern real??

r = -0.50P = 0.06

r = -0.24P = 0.39Fo

rb b

iom

ass (

g)

What did you find?

1989

1991

1993

1995

1997

1999

2001

2003

020406080

100120140160180

f(x) = − 0.18981173945445 x + 70.1205519404226R² = 0.00034495123509859

N-Linear (N-)N+Linear (N+)

1989

1991

1993

1995

1997

1999

2001

2003

0102030405060708090

100

N-Linear (N-)N+Linear (N+)

1989199

0199

1199

2199

3199

4199

5199

6199

7199

8199

9200

0200

1200

2200

30

0.5

1

1.5

2

2.5

3

3.5

N-Linear (N-)N+Linear (N+)

Richness and Biomass 1989-2003

1989199

0199

1199

2199

3199

4199

5199

6199

7199

8199

9200

0200

1200

2200

30

0.5

1

1.5

2

2.5

3

N-Linear (N-)N+Linear (N+)Linear (N+)

Rich

ness

Biom

ass

Grass Legume

Do grasses and legumes respond differently to N addition?

• How does N addition affect richness and productivity? ( or )

• Each group fill the table

Richness 2003

Biomass 2003

RichnessOver time

Biomass Over time

Grass

Legume

0

5

10

15

20

1985 1990 1995 2000 2005 2010 2015

Spec

ies R

ichn

ess

Year

- Fertilizer

+ Fertilizer

a Fertilizer: F1, 51.2 = 14.70; P < 0.001Year: F22, 198 = 6.73; P < 0.001Year x Fertilizer: F22, 198 = 1.53; P = 0.068

* ** *** **

***

area of sampling unit is 0.5m x 2m from 1992 onwards

0

5

10

15

20

25

30

35

1990 1995 2000 2005 2010 2015

sqrt

[Liv

e Bi

omas

s (g

m-2

)]

Year

- Fertilizer

+ Fertilizer

a Fertilizer: F1, 40.5 = 53.05; P < 0.001Year: F19, 169 = 7.51; P < 0.001Year x Fertilizer: F19, 169 = 1.53; P = 0.080

Comments/questions?

Richness 2003

Biomass 2003

RichnessOver time

Biomass Over time

Grass 0 0 - +Legume

- 0 - -

Functional Group RichnessData from year 2003