1. Biodiversity Species Richness and Physical Constraints Lab 2
Christine M. Rodrigue
Department of Geography
Environmental Science and Policy Program
California State University, Long Beach

2. Lab 2 Graphing how species richness varies with physical factors
Animal diversity depends on plant productivity
Plant productivity (carbon-fixing) depends on:
insolation intensity and daily duration (Lab 1)
water availability
Getting comfortable with spreadsheets
Download LibreOffice from
Graphing in Calc
Equation fitting in Calc
Download data from
should just open in Calc if you're in our labs
at home, save file first, then open Calc, and have it open file

3. Lab 2
Scatterplot 1
Diversity of mammal quadrupeds (4-legged) in huge quadrats (22,5002 mi.!) taken all over North and Central America
Plot species number against latitude:
highlight cells A4 through B51
click chart button up top
choose chart type X-Y scatter
next, next
install titles for graph and for its two axes
finish

4. Lab 2 Scatterplot 1 (continued)
If borders are grey, it's editable; if not, double-click it to make it editable
When editable, click on any dot (they all go green):
right-click, Insert Trend Line, and click Coëf. of Determination (R2)
you can also ask for the equation to show -- you may need to move this box around and format it to show 3 decimal places
experiment under the Type tab that comes up
watch changes in R2 as you click trend line, right click, and ask for different types (linear, logarithmic, exponential, power)
now try the polynomial equations of different degrees and find an order that gets above an R2 = but has the fewest terms in the equation above 0.900
note that that line visually matches the pattern in the dots: 3 bulges or plateaus, 3 downward slopes

5. Lab 2
Scatterplot 1 (continued)

6. Lab 2 Scatterplot 1 (continued)
Why is there, in general, an inverse relationship? (Lab 1)
Why is there a bump into higher diversity ~20°N?
Why does diversity drop ~25-30°N?
Why does it smooth out ~30-45°N?
Why does it resume dropping off ~45-55°N?
What's with the plateau around 55-65°N? (hint: Lab 1)
Why does it seem to turn down again around 70°N?
What about the residuals (departures from line)?
Where are the worst ones?
Think about the east-west differences along the coasts ~25-35°N?

7. Lab 2
Scatterplot 2: Tree species diversity going east to west around 35°N
This time highlight H4 through I15
X-Y scatterplot
Trend line (showing R2 and equation to 3 decimal places)
Curve now shows 2 peaks and 1 dip (so what degree polynomial?)
Where is diversity the highest?
Where is the second peak?
Where's the dip
What is the forcing variable here?

8. Lab 2
Scatterplot 2 (continued)

9. Lab 2
Scatterplot 3: Tree species going south to north along west coast
This time highlight H18 through I27
X-Y scatterplot
Trend line (showing R2 and equation to 3 decimal places)
Curve shows a pattern much like the mammalian quadrupeds
Where is diversity the highest?
Where does it drop?
Where does it plateau (and, indeed, rise a bit)?
Starts out kind of low (80 spp.) but stays higher longer
What are the forcing variables here?

10. Lab 2
Scatterplot 4: Tree species going south to north along east coast
This time highlight H30 through I39
X-Y scatterplot
Trend line (showing R2 and equation to 3 decimal places)
Curve shows a different pattern from west coast pattern
Where is diversity the highest?
Where does it drop?
Where does it plateau below ~20 spp.)?
Starts out much higher than west coast, but drops precipitously right where west coast is enjoying an increase in biodiversity
What are the forcing variables here?

11. Lab 2
Scatterplots 3 and 4 together

12. Lab 2
Useful context: Köppen climate map