Species Diversity as Related to Fire

Species diversity is a community-level characteristic. A community includes all the populations of organisms in a given area at some point in time. Species diversity is high when many equally or nearly equally abundant species are present. If a community only has a few species, or if only a few species are abundant, then species diversity is low. Usually, a high species diversity value indicates a complex community with many species interactions.


The following data points were estimated from Collins and Gibson1. Fire impacts both the number of plant species present and the abundance of each species. The following data were collected to assess the relationship between time in years since last fire and species diversity of plants.

Time

Species diversity

Time

Species diversity

0

3.9

3

5.6

0

4.1

3

6.9

0

4.2

3

7.5

0

4.5

4

5.9

0

4.7

5

6.2

0

5.0

6

6.8

0

5.1

7

6.6

0

5.2

8

9.9

2

7.2

10

5.8

15

5.4

10

6.6

2

7.1

10

7.5

15

6.4

11

5.2

1

4.6

12

5.3

1

4.7

12

5.4

1

5.3

12

5.8

1

5.8

13

5.2

1

6.1

13

5.3

16

4.7

13

5.9

16

5.7

14

5.2

2

4.1

14

5.7

2

4.3

14

5.8

2

7.1

15

6.4

Species diversity as related to fire

Using a statistical package or a graphing calculator, make a scatterplot of this data set with time as the independent variable and species diversity as the dependent variable.

Does it look linear or quadratic?

Fit a line and a quadratic to this data set and discuss which equation best fits the dataset. For a reminder of how to choose which equation is best go here.

For the quadratic equation, find the vertex and the x-intercepts.

Explain what the vertex is describing in this physical situation.

Are there any values for the independent variable that give unreasonable answers for the dependent variable? Explain.



1Collins, S. and D. J. Gibson, 1990, Effects of fire on community structure in tallgrass and mixed-grass prairie. pp. 81-98, University of Oklahoma Press, Norman.